J Mol Biol, 1999 Jun 11, 289(3), 517 - 27 A newly identified, essential catalytic residue in a critical secondary structure element in the integrase family of site-specific recombinases is conserved in a similar element in eucaryotic type IB topoisomerases; Cao Y et al.; The integrase family of site-specific recombinases catalyzes conservative rearrangements between defined segments of DNA . A highly conserved tetrad (RHRY) of catalytic residues is essential for this process . This tetrad is dispersed in two motifs in the linear sequence, but is configured appropriately in the catalytic pocket to execute the strand cleavage and rejoining reactions . A third conserved motif has been identified in the Xer subgroup of the integrase family . Mutational analysis of 12 conserved residues in this motif in the XerD protein from Salmonella typhimurium led to the identification of an essential fifth catalytic residue (lysine 172) which is implicated in strand cleavage or exchange . This lysine residue occupies part of the turn of an antiparallel beta-hairpin which forms one side of the catalytic cleft in XerD, and is found at similar positions among evolutionarily diverse integrase family members . Related antiparallel beta-hairpins are present in eucaryotic type IB topoisomerase enzymes which also contain a critical lysine residue in the turn of the hairpin . In both the integrase family and eucaryotic type IB topoisomerases, the catalytic lysine residues are in close contact with the substrates and may play similar roles in influencing the reactivity of the phosphotyrosine intermediates formed during reactions catalyzed by both enzymes . Biochemistry, 1999 Jun 1, 38(22), 7363 - 71 Mutagenesis of histidinol dehydrogenase reveals roles for conserved histidine residues; Teng H et al.; The dimeric zinc metalloenzyme L-histidinol dehydrogenase (HDH) catalyzes an unusual four-electron oxidation of the amino alcohol histidinol via the histidinaldehyde intermediate to the acid product histidine with the reduction of two molecules of NAD . An essential base, with pKa about 8, is involved in catalysis . Here we report site-directed mutagenesis studies to replace each of the five histidine residues (His-98, His-261, His-326, His-366, and His-418) in Salmonella typhimurium with either asparagine or glutamine . In all cases, the overexpressed enzymes were readily purified and behaved as dimers . Substitution of His-261 and His-326 by asparagine caused about 7000- and 500-fold decreases in kcat, respectively, with little change in KM values . Similar loss of activity was also reported for a H261N mutant Brassica HDH {Nagai, A., and Ohta, D . (1994) J . Biochem . 115, 22-25} . Kinetic isotope effects, pH profiles, substrate rescue, and stopped-flow experiments suggested that His-261 and His-326 are involved in proton transfers during catalysis . Sensitivity to metal ion chelator and decreased affinities for metal ions with substitutions at His-261 and His-418 suggested that these two residues are candidates for zinc ion ligands. Biochemistry, 1999 Jun 1, 38(22), 7355 - 62 Mechanism of Salmonella typhimurium histidinol dehydrogenase: kinetic isotope effects and pH profiles; Grubmeyer C et al.; L-Histidinol dehydrogenase catalyzes the biosynthetic oxidation of L-histidinol to L-histidine with sequential reduction of two molecules of NAD . Previous isotope exchange results had suggested that the oxidation of histidinol to the intermediate histidinaldehyde occurred 2-3-fold more rapidly than overall catalysis . In this work, we present kinetic isotope effects (KIE) studies at pH 9.0 and at pH 6.7 with stereospecifically mono- and dideuterated histidinols . The data at pH 9.0 support minimal participation of the first hydride transfer and substantial participation of the second hydride transfer in the overall rate limitation . Stopped-flow experiments with protiated histidinol revealed a small burst of NADH production with stoichiometry of 0.12 per subunit, and 0.25 per subunit with dideuterated histidinol, indicating that the overall first half-reaction was not significantly faster than the second reaction sequence . Results from kcat and kcat/KM titrations with histidinol, NAD, and the alternative substrate imidazolyl propanediol demonstrated an essential base with pKa values between 7.7 and 8.4 . In KIE experiments performed at pH 6.7 or with a coenzyme analogue at pH 9 . 0, the first hydride transfer became more rate limiting . Kinetic simulations based on rate constants estimated from this work fit well with a mechanism that includes a relatively fast, and thermodynamically unfavorable, hydride transfer from histidinol and a slower, irreversible second hydride transfer from a histidinaldehyde derivative . Thus, although the chemistry of the first hydride transfer is fast, both partial reactions participate in the overall rate limitation. Biochim Biophys Acta, 1999 May 18, 1431(2), 374 - 83 Interaction of FliI, a component of the flagellar export apparatus, with flagellin and hook protein; Silva-Herzog E et al.; FliI is a key component of the flagellar export apparatus in Salmonella typhimurium . It catalyzes the hydrolysis of ATP which is necessary for flagellar assembly . Affinity blotting experiments showed that purified flagellin and hook protein, two flagellar axial proteins, interact specifically with FliI . The interaction of either of the two proteins with FliI, increases the intrinsic ATPase activity . The presence of either flagellin or hook protein stimulates ATPase activity in a specific and reversible manner . A Vmax of 0.12 nmol Pi min-1 microgram-1 and a Km for MgATP of 0.35 mM was determined for the unstimulated FliI; the presence of flagellin increased the Vmax to 0.35 nmol Pi min-1 microgram-1 and the Km for MgATP to 1.1 mM . The stimulation induced by the axial proteins was fully reversible suggesting a direct link between the catalytic activity of FliI and the export process. Arch Toxicol, 1999 Mar, 73(2), 71 - 9 Enzyme-mediated dichloromethane toxicity and mutagenicity of bacterial and mammalian dichloromethane-active glutathione S-transferases; Gisi D et al.; The kinetic properties of bacterial and rat liver glutathione S-transferases (GST) active with dichloromethane (DCM) were compared . The theta class glutathione S-transferase (rGSTTI-1) from rat liver had an affinity for dihalomethanes lower by three orders of magnitude (K(app) > 50 mM) than the bacterial DCM dehalogenase/GST from Methylophilus sp . DM11 . Unlike the bacterial DCM dehalogenase, the rat enzyme was unable to support growth of the dehalogenase minus Methylobacterium sp . DM4-2cr mutant with DCM . Moreover, the presence of DCM inhibited growth with methanol of the DM4-2cr transconjugant expressing the rat liver GSTT1-1 . In Salmonella typhimurium TA1535, expression of rat and bacterial DCM-active GST from a plasmid in the presence of DCM yielded up to 5.3 times more reversions to histidine prototrophy in the transconjugant expressing the rat enzyme . Under the same conditions, however, GST-mediated conversion of DCM to formaldehyde was lower in cell-free extracts of the transconjugant expressing the rat GSTT1 than in the corresponding strain expressing the bacterial DCM dehalogenase . This provided new evidence that formaldehyde was not the main toxicant associated with GST-mediated DCM conversion, and indicated that an intermediate in the transformation of DCM by GST, presumably S-chloromethylglutathione, was responsible for the observed effects . The marked differences in substrate affinity of rat and bacterial DCM-active GST, as well as in the toxicity and genotoxicity associated with expression of these enzymes in bacteria, suggest that bacterial DCM dehalogenases/GST have evolved to minimise the toxic effects associated with glutathione-mediated catalysis of DCM conversion. J Toxicol Sci, 1999 May, 24(2), 87 - 94 Mutagenicity tests of 4-phenyl-1,3-dithia-2-thioxo-cyclopent-4-ene; Sadanobu S et al.; The mutagenicity of 4-phenyl-1,3-dithia-2-thioxo-cyclopent-4-ene (DT827B) was examined in reverse mutation tests using Salmonella typhimurium and Escherichia coli, in the chromosomal aberration test with Chinese hamster ovary (CHO) cells, and in the micronucleus test using mice bone-marrow . In reverse mutation assay on DT827B according to Ames' method, DT827B was not mutagenic to S . typhimurium or E . coli when tested in dimethylsulfoxide to the limit of its solubility where precipitation occurred . In chromosomal aberration assay using CHO cells, DT827B was not clastogenic to induce structural chromosomal aberration but capable of inducing polyploidy . In micronucleus test, DT827B did not show micronucleus-inducing potential at the maximum dose . In conclusion of the three mutagenicity studies, DT827B was considered to cause no mutagenicity under the conditions used in the present experiments except the increase in polyploidy, which probably is due to a toxic effect of the compound. J Bacteriol, 1999 Jun, 181(11), 3610 - 2 Salmonella typhimurium IroN and FepA proteins mediate uptake of enterobactin but differ in their specificity for other siderophores; Rabsch W et al.; Salmonella typhimurium possesses two outer membrane receptor proteins, IroN and FepA, which have been implicated in the uptake of enterobactin . To determine whether both receptors have identical substrate specificities, fepA and iroN mutants and a double mutant were characterized . While both receptors transported enterobactin, the uptake of corynebactin and myxochelin C was selectively mediated by IroN and FepA, respectively. J Bacteriol, 1999 Jun, 181(11), 3351 - 7 Mutant forms of Salmonella typhimurium sigma54 defective in transcription initiation but not promoter binding activity; Kelly MT et al.; Transcription initiation with sigma54-RNA polymerase holoenzyme (sigma54-holoenzyme) has absolute requirements for an activator protein and ATP hydrolysis . sigma54's binding to core RNA polymerase and promoter DNA has been well studied, but little is known about its role in the subsequent steps of transcription initiation . Following random mutagenesis, we isolated eight mutant forms of Salmonella typhimurium sigma54 that were deficient in transcription initiation but still directed sigma54-holoenzyme to the promoter to form a closed complex . Four of these mutant proteins had amino acid substitutions in region I, which had been shown previously to be required for sigma54-holoenzyme to respond to the activator . From the remaining mutants, we identified four residues in region III which when altered affect the function of sigma54 at some point after closed-complex formation . These results suggest that in addition to its role in core and DNA binding, region III participates in one or more steps of transcription initiation that follow closed-complex formation. Braz J Med Biol Res, 1999 Feb, 32(2), 241 - 6 New vaccine strategies against enterotoxigenic Escherichia coli . II: Enhanced systemic and secreted antibody responses against the CFA/I fimbriae by priming with DNA and boosting with a live recombinant Salmonella vaccine; Lasaro MO et al.; The induction of systemic (IgG) and mucosal (IgA) antibody responses against the colonization factor I antigen (CFA/I) of enterotoxigenic Escherichia coli (ETEC) was evaluated in mice primed with an intramuscularly delivered CFA/I-encoding DNA vaccine followed by two oral immunizations with a live recombinant Salmonella typhimurium vaccine strain expressing the ETEC antigen . The booster effect induced by the oral immunization was detected two weeks and one year after the administration of the DNA vaccine . The DNA-primed/Salmonella-boosted vaccination regime showed a synergistic effect on the induced CFA/I-specific systemic and secreted antibody levels which could not be attained by either immunization strategy alone . These results suggest that the combined use of DNA vaccines and recombinant Salmonella vaccine strains can be a useful immunization strategy against enteric pathogens. Appl Environ Microbiol, 1999 Jun, 65(6), 2396 - 401 Lethality of a heat- and phosphate-catalyzed glucose by-product to Escherichia coli O157:H7 and partial protection conferred by the rpoS regulon; Byrd JJ et al.; A by-product of glucose produced during sterilization (121 degrees C, 15 lb/in2, 15 min) at neutral pH and in the presence of phosphate (i.e., phosphate-buffered saline) was bactericidal to Escherichia coli O157:H7 (ATCC 43895) . Other six-carbon (fructose and galactose) and five-carbon (arabinose, ribose, and xylose) reducing sugars also produced a toxic by-product under the same conditions . Fructose and the five-carbon sugars yielded the most bactericidal activity . Glucose concentrations of 1% (wt/vol) resulted in a 99.9% decline in the CFU of stationary-phase cells per milliliter in 2 days at 25 degrees C . An rpoS mutant (pRR10::rpoS) of strain 43895 (FRIK 816-3) was significantly (P < 0.001) more sensitive to the glucose-phosphate by-product than the parent strain, as glucose concentrations from 0.05 to 0.25% resulted in a 2- to 3-log10 reduction in CFU per milliliter in 2 days at 25 degrees C . Likewise, log-phase cells of the wild-type strain, 43895, were significantly more sensitive (P < 0.001) to the glucose-phosphate by-product than were stationary-phase cells, which is consistent with the stability of rpoS and the regulation of rpoS-regulated genes . The bactericidal effect of the glucose-phosphate by-product was reduced when strains ATCC 43895 and FRIK 816-3 were incubated at a low temperature (4 degrees C) . Also, growth in glucose-free medium (i.e., nutrient broth) did not alleviate the sensitivity to the glucose-phosphate by-product and excludes the possibility of substrate-accelerated death as the cause of the bactericidal effect observed . The glucose-phosphate by-product was also bactericidal to Salmonella typhimurium, Shigella dysenteriae, and a Klebsiella sp . Attempts to identify the glucose-phosphate by-product were unsuccessful . These studies demonstrate the production of a glucose-phosphate by-product bactericidal to E . coli O157:H7 and the protective effects afforded by rpoS-regulated gene products . Additionally, the detection of sublethally injured bacteria may be compromised by the presence of this by-product in recovery media. Electrophoresis, 1999 Apr-May, 20(4-5), 813 - 7 Regulation of virulence genes by environmental signals in Salmonella typhimurium; Deiwick J et al.; Sensing and responding to environmental signals is a crucial element of bacterial pathogenicity . For a successful progression of infection, virulence gene expression is coordinated in response to habitat-specific environmental signals from the host organism . We are interested in identifying environmental cues affecting the expression of genes within Salmonella Pathogenicity Island 2 (SPI2), a virulence locus important for systemic infections by S . typhimurium . We describe our approach starting with the identification of new virulence genes, and analysis of the regulation of these genes by environmental signals leading to the proteome analysis in order to define the SPI2 regulon. Prev Vet Med, 1999 May 14, 40(1), 1 - 17 Generalised linear mixed models analysis of risk factors for contamination of Danish broiler flocks with Salmonella typhimurium; Chriel M et al.; We present a retrospective observational study of risk factors associated with the occurrence of Salmonella typhimurium (ST) in Danish broiler flocks . The study is based on recordings from 1994 in the ante-mortem database maintained by the Danish Poultry Council . The epidemiological units are the broiler flocks (about 4000 flocks) which are clustered within producers . Broiler flocks with ST-infected parent stocks show increased risk of salmonella infection, and also the hatchery affects the salmonella status significantly . Among the rearing factors, only the use of medicine as well as the time of rearing, and the sampling method are significant . Epidemiological control would seem most efficient on starting at the top levels of the production hierarchy from which a major part of the ST contamination is derived . A secondary purpose of the study is to evaluate different statistical approaches and software for the analysis of a moderately-sized data set of veterinary origin . We compare the results from five analyses of the generalised linear mixed model (GLMM) type . The first observation is that the results agree reasonably well and lead to similar conclusions . A closer look reveals certain patterns of bias and estimation accuracy that correspond well with theoretical findings and practical experience reported in the statistical literature. Microb Pathog, 1999 Jun, 26(6), 299 - 305 Comparison of the abilities of Salmonella typhimurium rpoS, aroA and rpoS aroA strains to elicit humoral immune responses in BALB/c mice and to cause lethal infection in athymic BALB/c mice; Coynault C et al.; Salmonella typhimurium rpoS and rpoS aroA mutants are effective live vaccines in the murine model of salmonellosis (Coynault et al., Mol . Microbiol . 1996; 22: 149-60) . Here, we further investigate the characteristics of these vaccines . The systemic humoral response induced by S . typhimurium rpoS, aroA and rpoS aroA vaccine candidates against S . typhimurium LPS was studied by ELISA . In BALB/c mice, the rpoS aroA strain induced a systemic anti-LPS humoral response similar to that induced by the rpoS and aroA strains . The virulence of aroA and rpoS aroA vaccines in nude (nu/nu) BALB/c mice was also compared . Salmonella typhimurium aroA and rpoS aroA vaccines both produced slowly progressing lethal infections in athymic mice inoculated i.p . but the rpoS aroA strain was more attenuated than the aroA strain, as determined by time to death and bacterial counts in spleens . Finally, a rpoS mutant of Salmonella dublin conferred protection in mice against an oral challenge with a wild-type strain of S . dublin whereas a rpoS mutant of S . typhimurium did not . This suggests that the protection provided by the S . typhimurium rpoS vaccine is serotype-dependent . JAMA, 1999 May 19, 281(19), 1811 - 6 Investigation of multidrug-resistant Salmonella serotype typhimurium DT104 infections linked to raw-milk cheese in Washington State; Villar RG et al.; CONTEXT: Multidrug-resistant Salmonella Typhimurium DT104 has recently emerged as a cause of human and animal illness in Europe and North America . In early 1997, health officials in Yakima County, Washington, noted a 5-fold increase in salmonellosis among the county's Hispanic population . OBJECTIVES: To characterize bacterial strains and identify risk factors for infection with Salmonella Typhimurium in Yakima County . DESIGN: Laboratory, case-control, and environmental investigations . SETTING AND PARTICIPANTS: Patients with culture-confirmed Salmonella Typhimurium infection living in Yakima County and age- and neighborhood-matched control subjects . MAIN OUTCOME MEASURES: Food vehicle implication based on case-control study and outbreak control . RESULTS: Between January 1 and May 5, 1997, 54 culture-confirmed cases of Salmonella Typhimurium were reported . The median age of patients was 4 years and 91% were Hispanic . Patients reported diarrhea (100%), abdominal cramps (93%), fever (93%), bloody stools (72%), and vomiting (53%); 5 patients (9%) were hospitalized . Twenty-two patients and 61 control subjects were enrolled in the case-control study . Seventeen case patients (77%) reported eating unpasteurized Mexican-style soft cheese in the 7 days before onset of illness compared with 17 control subjects (28%) (matched odds ratio, 32.3; 95% confidence interval, 3.0-874.6) . All case-patient isolates were phage definitive type 104 (DT104) (n = 10) or DT104b (n = 12), and 20 (91%) were resistant to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline . The cheese produced and eaten by 2 unrelated patients was made with raw milk traced to the same local farm . Milk samples from nearby dairies yielded Salmonella Typhimurium DT104 . The incidence of Salmonella Typhimurium infections in Yakima County returned to pre-1992 levels following interventions based on these findings . CONCLUSIONS: Multidrug-resistant Salmonella Typhimurium DT104 emerged as a cause of salmonellosis in Yakima County, and Mexican-style soft cheese made with unpasteurized milk is an important vehicle for Salmonella Typhimurium DT104 transmission . We postulate that recent increases in human salmonellosis reflect the emergence of Salmonella Typhimurium DT104 among dairy cows in the region . Continued efforts are needed to discourage consumption of raw milk products, promote healthier alternatives, and study the ecology of multidrug-resistant Salmonella Typhimurium. JAMA, 1999 May 19, 281(19), 1805 - 10 Two outbreaks of multidrug-resistant Salmonella serotype typhimurium DT104 infections linked to raw-milk cheese in Northern California; Cody SH et al.; CONTEXT: Salmonella serotype Typhimurium definitive type 104 (DT104), with resistance to 5 drugs (ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline), has emerged as the most common multidrug-resistant Salmonella strain in the United States . However, illnesses resulting from this strain have not been associated definitively with a source in this country . OBJECTIVE: To determine the source of 2 outbreaks of Salmonella Typhimurium DT104 . DESIGN: Matched case-control study conducted between March 24 and April 5, 1997 (outbreak 1), enhanced surveillance for new cases dating from February 1, 1997 (outbreak 2), and environmental and laboratory investigations . SETTING AND PARTICIPANTS: The case-control study included residents of 2 adjacent counties in northern California infected with the outbreak strain of Salmonella Typhimurium var Copenhagen and age-matched controls . For enhanced surveillance, a case was defined as Salmonella Typhimurium infection in a person exposed to fresh Mexican-style cheese . MAIN OUTCOME MEASURES: Risk factors for infection and source of implicated food . RESULTS: Outbreak 1 peaked in February 1997; 31 patients were confirmed by culture as having Salmonella Typhimurium var Copenhagen infection, isolates of which showed indistinguishable pulsed-field gel electrophoresis (PFGE) patterns . The outbreak strain was phage type DT104 with the 5-drug resistance pattern . Sixteen cases and 25 controls were enrolled in the case-control study; 15 of 16 Salmonella Typhimurium var Copenhagen cases compared with 14 of 24 matched controls reported eating unpasteurized Mexican-style cheese, (matched odds ratio, 7.9; 95% confidence interval, 1.1-354.9) . Enhanced surveillance uncovered outbreak 2, which peaked in April 1997 and was caused by a non-Copenhagen variant of Salmonella Typhimurium . During outbreak 2, Salmonella Typhimurium was isolated from 79 persons who ate fresh Mexican-style cheese from street vendors and from cheese samples and raw milk . The PFGE pattern of the milk isolate matched 1 of the 3 patterns recovered from patients; all strains were phage type DT104b with the 5-drug resistance pattern . CONCLUSION: Raw-milk products pose a risk for multidrug-resistant Salmonella Typhimurium DT104 infections. Regul Toxicol Pharmacol, 1999 Apr, 29(2 Pt 2), S36 - 42 Genotoxicity tests on D-tagatose; Kruger CL et al.; D-tagatose is a low-calorie sweetener that tastes like sucrose . Its genotoxic potential was examined in five standard assays: the Ames Salmonella typhimurium reverse mutation assay, the Escherichia coli/mammalian microsome assay, a chromosomal aberration assay in Chinese hamster ovary cells, a mouse lymphoma forward mutation assay, and an in vivo mouse micronucleus assay . D-tagatose was not found to increase the number of revertants per plate relative to vehicle controls in either the S . typhimurium tester strains or the WP2uvrA- tester strain with or without metabolic activation at doses up to 5000 microg/plate . No significant increase in Chinese hamster ovary cells with chromosomal aberrations was observed at concentrations up to 5000 microg/ml with or without metabolic activation . D-tagatose was not found to increase the mutant frequency in mouse lymphoma L5178Y cells with or without metabolic activation up to concentrations of 5000 microg/ml . D-tagatose caused no significant increase in micronuclei in bone marrow polychromatic erythrocytes at doses up to 5000 mg/kg . D-tagatose was not found to be genotoxic under the conditions of any of the assays described above . Regul Toxicol Pharmacol, 1999 Apr, 29(2 Pt 1), 205 - 10 Genotoxicity evaluation of wood-derived and vegetable oil-derived stanol esters; Turnbull D et al.; Plant stanol esters from wood and vegetable oil sources were tested for genotoxicity in bacterial (Salmonella typhimurium) and mammalian cell (L5178Y) gene mutation assays and in a mammalian cell chromosome aberration assay (CHO cells) . The two stanol ester formulations were tested separately at doses up to the limit of solubility, with and without the addition of an Aroclor-induced rat liver microsome metabolic activation system (S9 mix) . All tests were performed in duplicate and gave negative results for both wood and vegetable oil stanol ester formulations . Thus, plant stanol esters are not genotoxic under the conditions of exposure tested . J Food Prot, 1999 May, 62(5), 474 - 9 The effectiveness of triclosan-incorporated plastic against bacteria on beef surfaces; Cutter CN; Triclosan is a nonionic, broad-spectrum, antimicrobial agent that has been incorporated into a variety of personal hygiene products, including hand soaps, deodorants, shower gels, mouthwashes, and toothpastes . In this study, plastic containing 1,500 ppm of triclosan was evaluated in plate overlay assays and meat experiments as a means of reducing populations of bacteria . Plate overlay assays indicated that the triclosan-incorporated plastic (TIP) inhibited the following organisms: Brochothrix thermosphacta ATCC 11509, Salmonella Typhimurium ATCC 14028, Staphylococcus aureus ATCC 12598, Bacillus subtilis ATCC 6051, Shigella flexneri ATCC 12022, Escherichia coli ATCC 25922, and several strains of E . coli O157:H7 . In meat experiment 1, irradiated, lean beef surfaces inoculated with B . thermosphacta, Salmonella Typhimurium, E . coli O157:H7, or B . subtilis were covered with TIP, vacuum packaged, and stored for 24 h at 4 degrees C . Of the organisms tested, only populations of B . thermosphacta were slightly reduced . In meat experiment 2, prerigor beef surfaces were inoculated with E . coli O157: H7, Salmonella Typhimurium, or B . thermosphacta incubated at 4 degrees C for 24 h, wrapped in TIP or control plastic, vacuum packaged, and stored at 4 degrees C for up to 14 days . There was a slight reduction in the population of the organisms after initial application with TIP . However, bacterial populations following long-term, refrigerated (4 degrees C), vacuum-packaged storage up to 14 days were not statistically (P< or =0.05) or numerically different than controls . In meat experiment 3, even TIP-wrapped, vacuum-packaged beef samples that were temperature abused at 12 degrees C did not exhibit significant (P< or =0.05) or sustainable reductions after 14 days of 4 degrees C storage . Another study indicated that populations of E . coli O157:H7 or B . thermosphacta added directly to TIP were not affected after 2 h of refrigerated storage or that the antimicrobial activity could be extracted from the plastic . Additional experiments suggest that presence of fatty acids or adipose may diminish the antimicrobial activity of TIP on meat surfaces . This study demonstrates that while antimicrobial activity is detected against bacterial cultures in antimicrobial plate assays, plastic containing 1,500 ppm of triclosan does not effectively reduce bacterial populations on refrigerated, vacuum-packaged meat surfaces. J Food Prot, 1999 May, 62(5), 431 - 7 Development of a rapid response biosensor for detection of Salmonella typhimurium; Seo KH et al.; An integrated optic interferometer for detecting foodborne pathogens was developed . The interferometer is a planar waveguide with two thin antibody-coated channels of immunochemically selective agents that interact with antigen molecules . One channel is coated with antibody to Salmonella as a sample, and the other is coated with human immunoglobulin G as a reference channel by using reductive amination . Salmonella was introduced onto the sensing channels through the flow cell on the channels . Phase shift (pi) generated by refractive index variation, as determined by interfering the perturbed sample channel with an unperturbed reference channel and observing the fringe shift, was used for detection . Salmonella Typhimurium (heat-treated or boiled) was detected by binding to antibody against Salmonella common structural antigen immobilized on a silane-derived sensor surface at concentrations in the range of 1x10(5) to 1x10(7) CFU/ml . Salmonella (1x10(7) CFU/ml) mixed with Escherichia coli (1x10(7) CFU/ml) were readily detected without any decrease in sensitivity by the direct assay . Application of a sandwich assay with a second antibody or a gold-conjugated antibody increased the detection limit to 1x10(5) CFU/ml within a 10-min reaction time . Various methods for the immobilization of the capture antibody to the biosensor channels were compared . The greatest binding response was observed in a direct reductive amination method with a long reaction period and increased the detection limit of direct binding of Salmonella antigen to 1x10(4) CFU/ml . The biosensor was able to detect Salmonella Typhimurium in chicken carcass wash fluid originally inoculated at a level of 20 CFU/ml after 12 h of nonselective enrichment . The planar optic biosensor shows promise as a fast, sensitive, reliable, and economical means of detecting food pathogens in the future. FEMS Microbiol Lett, 1999 May 15, 174(2), 327 - 32 A new chloramphenicol and florfenicol resistance gene flanked by two integron structures in Salmonella typhimurium DT104; Arcangioli MA et al.; A new chloramphenicol resistance gene from Salmonella typhimurium DT104, designated floR, also conferring resistance to florfenicol, was characterized . Sequence analysis of the deduced FloR protein suggested that it belongs to the 12-TMS (transmembrane segments) multidrug efflux pumps family . The floR gene, and the downstream sequenced tetR and tetA tetracycline resistance genes, were surrounded by two class 1 integrons . The first one contained the resistance gene aadA2 and a deleted sulI resistance gene . The second one contained the beta-lactamase gene pse1 and a complete sulI gene . Thus, the floR gene is included in a multiresistance locus of at least 12.5 kb . Its particular organization and chromosomal location could be involved in the antibioresistance pattern stability of the DT104 Salmonella typhimurium strains. Infect Immun, 1999 Jun, 67(6), 3121 - 7 Porcine epithelial beta-defensin 1 is expressed in the dorsal tongue at antimicrobial concentrations; Shi J et al.; Epithelial cells and phagocytes contain antimicrobial polypeptides that participate in innate host defense . A recently cloned porcine beta-defensin, PBD-1, was detected by Northern organ blots exclusively in the tongue epithelium . We generated recombinant PBD-1 peptide by using a baculovirus-insect cell expression system and obtained two forms (PBD-142 and PBD-138), which differed by N-terminal truncation . Only PBD-142 was found in scrapings of the surface of the dorsal tongue or the buccal mucosa . Immunohistochemical staining with antibody to PBD-142 revealed that PBD-1 was highly concentrated in an approximately 0.1-mm-thick layer in the cornified tips of the filiform (but not fungiform) papillae of the dorsal tongue and in the superficial squamous cell layers of the buccal mucosa . By scraping, extraction, and semiquantitative Western blotting, the concentration of PBD-1 in the dorsal tongue surface and the buccal mucosa was estimated at 20 to 100 micrograms/ml . PBD-1 had antibacterial activity against Escherichia coli, Salmonella typhimurium, Listeria monocytogenes, and Candida albicans in 10 mM sodium phosphate buffer (pH 7.4) . Added NaCl progressively inhibited the activity of PBD-1 against E . coli and C . albicans . In 10 mM sodium phosphate with 125 mM NaCl, the combinations of sublethal concentrations of PBD-1 and the porcine neutrophil peptide PG-3, PR-39, or PR-26 showed synergistic activity against E . coli or the multidrug-resistant S . typhimurium DT104 . At its physiologic concentration, PBD-1 has antimicrobial effects under both low- and high-salt conditions encountered in the oral cavity and may contribute to the antimicrobial barrier properties of the dorsal tongue and oral epithelium. Infect Immun, 1999 Jun, 67(6), 2815 - 21 Evaluation of Salmonella typhimurium mutants in a model of experimental gastroenteritis; Everest P et al.; Salmonella typhimurium strains harboring independent, defined mutations in aroA, invA, ssrA, or msbB were assessed for their ability to induce fluid accumulation, tissue damage, and local inflammation in rabbit ileal loops . Three wild-type strains of S . typhimurium, TML, HWSH, and SL1344, and two mutant strains, S . typhimurium SL1344 ssrA and S . typhimurium SL1344 msbB, consistently induced fluid accumulation in the lumen of loops and inflammation of loop-associated tissues . In contrast, three different S . typhimurium aroA strains and an invA mutant of SL1344 did not induce significant fluid accumulation in the rabbit ileal loops . However, the S . typhimurium aroA strains did induce an inflammatory infiltrate and some local villus-associated damage, but the invA mutant did not . Histologically, wild-type S . typhimurium, S . typhimurium SL1344 ssrA, and S . typhimurium SL1344 msbB demonstrated more severe effects on villus architecture than S . typhimurium aroA strains, whereas S . typhimurium invA-infected loops showed no detectable damage . This suggests that villus damage most likely contributes to fluid accumulation within the loop. Biotechniques, 1999 May, 26(5), 892 - 4, 896, 898 passim Increasing DNA transfer efficiency by temporary inactivation of host restriction; Edwards RA et al.; E . coli and Salmonella typhimurium are widely used bacterial hosts for genetic manipulation of DNA from prokaryotes and eukaryotes . Introduction of foreign DNA by electroporation or transduction into E . coli and Salmonella is limited by host restriction of incoming DNA by the recipient cells . Here, we describe a simple method that temporarily inactivates host restriction, allowing high-frequency DNA transfer . This technique might be readily applied to a wide range of bacteria to increase DNA transfer between strains and species. Environ Mol Mutagen, 1999, 33(3), 240 - 8 VITOTOX bacterial genotoxicity and toxicity test for the rapid screening of chemicals; Verschaeve L et al.; The VITOTOX test is a new bacterial genotoxicity test that was previously shown to be very rapid and sensitive . Initially only one Salmonella typhimurium strain (TA104 recN2-4) was used in the test . In this paper we introduce a second strain (TA104pr1) that can be used as an internal control to further enhance the reliability of the test . We demonstrate the usefulness of this pr1 strain in genotoxicity and toxicity testing . We also report on the results of a study where the VITOTOX test was performed on newly synthesized pharmaceutical compounds, or intermediate products in the synthesis of drug candidates . We demonstrate that the test gives identical results when performed independently in two different laboratories and that it correlates well with either the Ames test or SOS chromotest. Environ Mol Mutagen, 1999, 33(3), 202 - 10 Combinations of chlorocatechols and heavy metals cause DNA degradation in vitro but must not result in increased mutation rates in vivo; Schweigert N et al.; Chlorocatechols introduced into the environment directly or as a result of degradation processes are highly toxic, particularly when combined with heavy metals . With in vitro DNA degradation assays, the high reactivity of chlorocatechols combined with heavy metals could be shown, whereby copper was shown to be more active than iron . Structure-activity analysis showed that the degradation potential of the chlorocatechols decreased with an increasing number of chloratoms . The addition of reactive oxygen species scavengers allowed the identification of hydrogen peroxide as an important agent leading to DNA damage in this reaction . The potential of other reactive compounds, however, can neither be determined nor excluded with this approach . Exposure of Escherichia coli and Salmonella typhimurium cultures to the same mixtures of chlorocatechols and copper surprisingly did not lead to an enhanced mutation rate . This phenomenon was explained by doing marker gene expression measurements and toxicity tests with E . coli mutants deficient in oxidative stress defense or DNA repair . In catechol-copper-exposed cultures an increased peroxide level could indeed be demonstrated, but the highly efficient defense and repair systems of E . coli avoid the phenotypical establishment of mutations . Increased mutation rates under chronic exposure, however, cannot be excluded. Mutat Res, 1999 May 17, 441(2), 205 - 13 Substituent effect of a fluorine atom on the mutagenicity of nitroquinolines; Saeki K et al.; Some 16 nitroquinolines (NQs) and their fluorinated derivatives were tested for mutagenicity in Salmonella typhimurium TA100 without S9 mix to investigate the effect of fluorine-substitution on the mutagenicity . These NQs consist of 5-NQs, 5-nitroquinoline N-oxides (5-NQOs), N-methyl-5-nitroquinolinium methanesulfonates (N-Me-5-NQs) and 8-NQs, including three ortho-F-NQs, one meta-F-NQ, four para-F-NQs and four 3-F-NQs . For this purpose, eight F-NQs were newly synthesized . The data indicated that the ratio of the mutagenic activities (revertants/plate/nmol) of fluorinated NQs to those of the corresponding parent non-fluorinated compounds ranged from 0.6- to 119-fold . The fluorine atom located para to the nitro group markedly enhanced the mutagenicity (24-fold and more), while three ortho-fluorinated derivatives showed no significant increase in mutagenicity (enhancement ratio were 0.6, 0.8 and 1.7) . With respect to 8-NQs, its meta-fluorinated derivative also had an enhanced mutagenicity over the parent compound (53-fold) . In addition, although N-Me-5-NQ was less mutagenic than 5-NQ and 5-NQO, the mutagenicity of N-Me-5-NQ was most significantly enhanced by fluorine-substitution . These results suggest that introduction of a fluorine atom to the molecule in question may be a useful tool to modify their mutagenic potency and to better understand the mechanism of mutation . Mol Biol Evol, 1999 Apr, 16(4), 512 - 24 CRITICA: coding region identification tool invoking comparative analysis; Badger JH et al.; Gene recognition is essential to understanding existing and future DNA sequence data . CRITICA (Coding Region Identification Tool Invoking Comparative Analysis) is a suite of programs for identifying likely protein-coding sequences in DNA by combining comparative analysis of DNA sequences with more common noncomparative methods . In the comparative component of the analysis, regions of DNA are aligned with related sequences from the DNA databases; if the translation of the aligned sequences has greater amino acid identity than expected for the observed percentage nucleotide identity, this is interpreted as evidence for coding . CRITICA also incorporates noncomparative information derived from the relative frequencies of hexanucleotides in coding frames versus other contexts (i.e., dicodon bias) . The dicodon usage information is derived by iterative analysis of the data, such that CRITICA is not dependent on the existence or accuracy of coding sequence annotations in the databases . This independence makes the method particularly well suited for the analysis of novel genomes . CRITICA was tested by analyzing the available Salmonella typhimurium DNA sequences . Its predictions were compared with the DNA sequence annotations and with the predictions of GenMark . CRITICA proved to be more accurate than GenMark, and moreover, many of its predictions that would seem to be errors instead reflect problems in the sequence databases . The source code of CRITICA is freely available by anonymous FTP (rdp.life.uiuc.edu in/pub/critica) and on the World Wide Web rdpwww.life.uiuc.edu). Mikrobiol Z, 1999 Jan-Feb, 61(1), 32 - 45 {The antibacterial efficacy of preparations of interferon and its inducers}; Spivak NIa et al.; Experimental data have been presented which prove antibacterial efficiency of interferon preparations and inducers under infection processes evoked by Staphylococcus aureus, Salmonella typhimurium, Pseudomonas aeruginosa, Klebsiella pneumoniae . It is shown that the system of phagocytizing cells and natural cells-killers plays the basic protective role in the organism under the persistence of these microbes . The basic regularities of activating effect of interferon preparations and its inducers on the functional activity of the above mentioned cells have been found . The methods of treatment with interferon drugs based on experimental data have been developed for the first time . They were used to cure patients with pyo-septic diseases. Aust N Z J Public Health, 1999 Apr, 23(2), 164 - 7 Consumer attitudes and behaviours--key risk factors in an outbreak of Salmonella typhimurium phage type 12 infection sourced to chicken nuggets; Kenny B et al.; OBJECTIVES: To identify the source and intervention methods for an outbreak of Salmonella Typhimurium phage type 12 in South Australia . METHOD: Ten cases of S . Typhimurium phage type (PT) 12 infection were notified in South Australia in a four-week period from 7 May 1998 . Nine cases and 27 controls were included in a case control study to test the hypothesis that illness was associated with the consumption of chicken nuggets . RESULTS: A significant association between illness and the consumption of one brand of chicken nuggets was determined, odds ratio undefined (95% CI undefined; p = undefined) . Nine of nine cases and one of 27 controls reported eating these chicken nuggets . S . Typhimurium PT 12 was isolated from an opened sample of this particular brand of nuggets which had been retrieved from the home of one case . CONCLUSIONS AND IMPLICATIONS: The implicated nuggets were essentially a raw product which had been 'flash fried' in contrast with other brands which were fully cooked . The investigation highlighted issues of inadequate labelling and consumer responses to labelling information which affect food safety . A media release to highlight to the consumer the need to cook frozen food properly and a voluntary recall of the 'flash fried' product was instigated as a result of these conclusions . Further action is needed to eliminate the potential hazard that consumers will perceive and handle 'flash fried' nuggets as if they are a cooked chicken product. Aust Vet J, 1999 Apr, 77(4), 229 - 32 Concurrent Aelurostrongylus abstrusus infection and salmonellosis in a kitten; Barrs VR et al.; A 14-week-old kitten had a history of vomiting, diarrhoea and pyrexia, all of which resolved without treatment . Three weeks later the kitten developed a violent non-productive dry cough . Thoracic radiographs revealed pneumothorax and nodular alveolar disease . Aelurostrongylus abstrusus larvae and intracellular Gram-negative bacilli were seen in bronchial wash fluid and pleural exudate, and Salmonella Typhimurium was cultured from both fluids but not from faeces . Therapy included unilateral closed-tube thoracostomy, enrofloxacin and fenbendazole . Historical signs were compatible with gastrointestinal salmonellosis and secondary broncho-pneumonia . Seeding of the lungs with salmonellae may have occurred as a result of migration of A abstrusus from a gastro-intestinal tract residually infected or colonised by S Typhimurium . Alternatively, the development of lungworm infection in the cat may have activated quiescent S Typhimurium pulmonary granulomata from bacteraemia secondary to gastro-intestinal salmonellosis . Two years after diagnosis the cat was reportedly in good health. EMBO J, 1999 May 17, 18(10), 2886 - 96 Mutations which alter the elbow region of tRNA2Gly reduce T4 gene 60 translational bypassing efficiency; Herr AJ et al.; Translating ribosomes bypass a 50 nucleotide coding gap in bacteriophage T4 gene 60 mRNA between codons 46 and 47 in order to synthesize the full-length protein . Bypassing of the coding gap requires peptidyl-tRNA2Gly detachment from a GGA codon (codon 46) followed by re-pairing at a matching GGA codon just before codon 47 . Using negative selection, based on the sacB gene from Bacillus subtilis, Escherichia coli mutants were isolated which reduce bypassing efficiency . All of the mutations are in the gene for tRNA2Gly . Most of the mutations disrupt the hydrogen bonding interactions between the D- and T-loops (G18*psi55 and G19*C56) which stabilize the elbow region in nearly all tRNAs . The lone mutation not in the elbow region destabilizes the anticodon stem at position 40 . Previously described Salmonella typhimurium mutants of tRNA2Gly, which reduce the stability of the T-loop, were also tested and found to decrease bypassing efficiency . Each tRNA2Gly mutant is functional in translation (tRNA2Gly is essential), but has a decoding efficiency 10- to 20-fold lower than wild-type . This suggests that rigidity of the elbow region and the anticodon stem is critical for both codon-anticodon stability and bypassing. J Mol Biol, 1999 Apr 23, 288(1), 165 - 75 Protein-ligand interaction: grafting of the uridine-specific determinants from the CytR regulator of Salmonella typhimurium to Escherichia coli CytR; Thomsen LE et al.; Members of the LacI family of transcriptional repressors respond to the presence of small effector molecules . The binding of the ligands affect the proteins ability to repress transcription by stabilizing a conformation that, in most cases, is unfavorable for high-affinity DNA binding . The CytR anti-activator diverges from the other family members by relying on the cooperative DNA binding with the global regulator CRP . The inducers of CytR do not affect CytR-DNA binding per se, but alleviate repression by interrupting protein-protein interactions between the two regulators . Here, we have studied of the CytR-inducer interaction by exploring a discrepancy in the inducer response observed for the homologous CytR regulators of Escherichia coli and Salmonella typhimurium . CytR of S . typhimurium (CytRSt) appears to respond to the presence of both uridine and cytidine nucleosides, whereas E . coli CytR (CytREc) responds to cytidine only . We have used a combination of genetic and structural modeling studies to provide detailed information regarding the nature of this discrepancy . By analysis of hybrid CytR proteins followed by site-directed mutagenesis, we have successfully transferred the specificity determinants for uridine from CytRSt to CytREc, revealing that serine substitutions of only two residues (G131 and A152) in CytREc is required to make CytREc sensitive to uridine . In addition, by employing a genetic screen for induction of defective mutants, we have identified four amino acid residues in CytRSt that appear to be important for the response to uridine . The implications of these findings for the understanding of the ligand binding and induction of CytR are discussed in the context of the structural knowledge of CytR and homologous protein-ligand complexes . J Math Biol, 1999 Apr, 38(4), 359 - 75 Model and analysis of chemotactic bacterial patterns in a liquid medium; Tyson R et al.; A variety of spatial patterns are formed chemotactically by the bacteria Escherichia coli and Salmonella typhimurium . We focus in this paper on patterns formed by E . coli and S . typhimurium in liquid medium experiments . The dynamics of the bacteria, nutrient and chemoattractant are modeled mathematically and give rise to a nonlinear partial differential equation system . We present a simple and intuitively revealing analysis of the patterns generated by our model . Patterns arise from disturbances to a spatially uniform solution state . A linear analysis gives rise to a second order ordinary differential equation for the amplitude of each mode present in the initial disturbance . An exact solution to this equation can be obtained, but a more intuitive understanding of the solutions can be obtained by considering the rate of growth of individual modes over small time intervals. Intervirology, 1998, 41(6), 238 - 43 Antiviral efficacy of disinfectant solution MRI-1; Skinner GR et al.; Disinfectant MRI-1 was prepared by dissolution of non-ionic and ionic detergent in ethanol . The disinfectant inactivated extracellular and intracellular enveloped and non-enveloped viruses including herpes viruses, influenza A and human immunodeficiency disease virus in suspension or on surfaces by pre-exposure or post-exposure to the disinfectant; in addition, cells were disabled as potential hosts for viral infection using concentrations of MRI-1 which were 50-fold less than the operative concentration for disinfection . There was no evidence of in vitro mutagenicity using Salmonella typhimurium or sensitization or other adverse effect in a guinea pig model or in human subjects. Mol Gen Genet, 1999 Apr, 261(3), 472 - 9 A coding segment of the virulence regulatory gene spvR enhances expression of spvR-lacZ and spvR-gfp translational fusions in Salmonella typhimurium; Robbe-Saule V et al.; The Salmonella gene spvR is regulated by RpoS, and encodes an autoregulatory DNA-binding protein of the LysR family, which is required for transcriptional activation of the virulence operon spvABCD . We found that the 12-bp sequence between codons 3 and 8 of spvR (12bp-box) increased the expression of spvR'-lacZ translational fusions by at least two orders of magnitude . The 12bp-box did not affect the level of expression of a transcriptional spvR'-lacZ fusion, as determined by measurement of beta-galactosidase activity and mRNA levels . This suggests that the 12bp-box does not play a major role at the transcriptional level . However, the amounts of both SpvR-LacZ hybrid protein and lacZ mRNA produced from a translational spvR'-lacZ fusion were significantly lower if the 12bp-box was removed . Thus, the 12bp-box directly or indirectly affects the amount of spvR'-lacZ mRNA produced from a translational fusion but not from a transcriptional fusion . The 12bp-box still appeared to be functional when the spvR'-lacZ mRNA was elongated at its 5' end . In that case, however, while the 12bp-box greatly reduced the level of downstream mRNA produced, it did not affect the level of upstream mRNA . The effect of the 12bp-box was not restricted to lacZ fusions because expression of a translational spvR'-gfp fusion was also decreased by removal of the 12bp-box . The sequence of the 12bp-box is complementary to a sequence near the decoding region of 16S rRNA thought to be involved in translation initiation . This box may thus function as a translational enhancer, in which case the effect of the 12bp-box on lacZ mRNA levels might result indirectly from the tight coupling of translation and mRNA degradation . However, a direct role of the 12bp-box in increasing mRNA stability or in reducing the incidence of premature termination of transcription cannot be excluded. Int Immunol, 1999 Apr, 11(4), 481 - 9 Th1 dominance in the immune response to live Salmonella typhimurium requires bacterial invasiveness but not persistence; Pashine A et al.; Factors responsible for the predictable generation of Th1 or Th2 immune responses to microorganisms in vivo are not well characterized, although the ability of antigen presenting cells (APC) to provide co-stimulation, the kinetics of MHC-peptide ligand generation as well as the cytokine environment are all considered important factors for the differential Th1/Th2 priming of T cells . Our earlier findings of an IFN-gamma-dominant, Th1-type response to live Salmonella typhimurium (Stm) and a Th2-type response to killed Stm suggested that persistence of viable bacteria might be an important factor in the generation of IFN-gamma-dominant responses . Using genetically susceptible and resistant strains of mice to limit bacterial replication and persistence in vivo, we show that mice of the lty(r) genotype, capable of a 10-fold better clearance of Stm, mount an IFN-gamma-dominant immune response following immunization with live Stm similar to that in the lty(s) strain . Further, metabolically defective mutants of Stm, aroA and purA, when used in the live form, also elicit IFN-gamma-dominant immune responses similar to the wild-type Stm strain despite their inability to proliferate in vivo . While a laboratory strain of Escherichia coli, which is antigenically cross-reactive but non-invasive, elicits hardly any IFN-gamma in immune responses, an invasive strain of E . coil induces an IFN-gamma-dominant response . These data together indicate that, while entry of bacteria into macrophages is likely to be critical for the generation of IFN-gamma-dominant immune responses, their persistence is not. Zhonghua Yu Fang Yi Xue Za Zhi, 1998 Mar, 32(2), 70 - 2 {Studies on mutagenicity of humic acid samples collected from arsenosis-affected areas in China}; Yu X et al.; OBJECTIVE: To explore whether there is mutagenicity of humic acid samples collected from arsenosis affected areas in China . METHODS: Ames' test was used for natural humic acid samples extracted from the coal containing high arsenic in Guizhou Province, and the well water in the areas with blackfoot disease in Taiwan and with arsenosis in Inner Mongolia of China . RESULTS: Coefficients of revertant mutation were 1.02-0.82 net revertant per microgram (rev/microgram) of humic acid extracted from the coal containing high arsenic in Guizhou without rat liver homogenate (-S9), and 1.53-1.12 rev/microgram of that with rat liver homogenate (+S9), with an obvious dose-response relationship . CONCLUSION: Humic acid extracted from the coal containing high arsenic produced in Guizhou could cause stronger direct mutation in Salmonella typhimurium TA98 (frameshift mutation) and that extracted from the well water in the areas with blackfoot disease in Taiwan could cause weaker direct mutation in Salmonella typhimurium (-S9), but that extracted from the well water with arsenosis in Inner Mongolia could not cause mutation . Mutagenicity of commercial humic acid, purchased from Aldrich Co . in the United States, arsenic and iron was also studied, and no mutagenicity was found for them independently, but arsenic combined with humic acid, at certain concentrations, could cause weak mutation in TA98 (-S9), with or without iron . No mutagenicity in TA100 (+/- S9, base pair substitution mutation) was found in all the samples mentioned above. Zhonghua Yu Fang Yi Xue Za Zhi, 1998 Jul, 32(4), 214 - 8 {Plasmid profile typing of Salmonella typhimurium and its distribution in some provinces and cities of China}; Pan R et al.; OBJECTIVE: To study the relationship between the infection and prevalence of Salmonella typhimurium . METHODS: From 1980 to 1995, when Salmonella typhimurium infection was prevalent in north and south China, a total of 2,655 isolates of Salmonella typhimurium were collected from 19 provinces, municipalities, and autonomous regions and Hong Kong Special Administrative Region for plasmid profile analysis . The profiles consisting of some small plamids were recorded with capital letters A to J, and the profile which was free from small plasmid was recorded with capital letter O . Large plasmid in molecular weights of 140-20 Mdal showing in profiles was recorded with Arabic numerals 9 to 0 respectively . Having two or more than two large plasmids, the profile was recorded with two or more Arabic numerals . RESULTS: The 2,655 strains were divided into 11 plasmid profile groups and 168 plasmid profile types . Of 52 plasmid profile types frequently isolated, plasmid profile type O 4 was distributed extensively in 16 provinces, municipalities, and autonomous rehions and Hong Kong . Plasmid profile type O 5 was isolated in 5 provinces and Hong Kong, mostly in Jiangxi and Hubei . Plasmid profile type J 4 was isolated in 7 provinces, municipalities and autonomous regions, mostly in Jiangxi . Five plasmid profile types of Group A caused a big prevalence of nosocomial infection in Henan . Type A 6 was also isolated in Xinjiang and Anhui . Six plasmid profile types of Group E were prevalent in Xinjiang predominantely, three types caused nosocomial infection in Shanghai, type E 82 caused nosocomial infection and food poisoning in Liaoning . Type F 4 was isolated in 4 provinces, mostly in jiangxi and Fujian . Many plasmid profile types were prevalent local . Types B 5, BCEG 60, BE 6, B' 0 G 6, G 5 and EG 6 were prevalent in Jiangxi, Types IF'4, IF'H40 and F 9864 were prevalent in Sandong, Type IF'4 was also isolated in Jiangsu and Hubei, Type IF 40 in Anhui, Type BH 6 in Huibei, and Type EH 5 in Fujian . CONCLUSION: Plasmid profile analysis showed the same types in the prevance but different plasmid profiles in different provinces. J Bacteriol, 1999 May, 181(10), 3096 - 104 A HilA-independent pathway to Salmonella typhimurium invasion gene transcription; Rakeman JL et al.; Salmonella typhimurium invasion of nonphagocytic cells requires the expression of a type III secretion system (TTSS) encoded within Salmonella pathogenicity island 1 (SPI1) . TTSS gene transcription is activated in response to environmental signals and requires transcriptional regulators encoded within (HilA) and outside (SirA) SPI1 . Two unique loci, sirB and sirC, which contribute to SPI1 gene transcription were defined . sirC is an SPI1-encoded transcription factor of the AraC family that contributes to the invasive phenotype . sirB is required for maximal expression of sirC and consists of two open reading frames located near kdsA, a gene involved in lipopolysaccharide biosynthesis . sirC expression, unlike expression of other SPI1 genes, does not require HilA . Overexpression of sirC or sirA restores expression of a subset of SPI1 genes, including invF and sspC, in the absence of HilA . These data define roles for SirC and SirA as part of a HilA-independent pathway to SPI1 gene expression . We postulate that HilA-independent activation of inv expression is important for efficient assembly and function of the SPI1 TTSS. Biochim Biophys Acta, 1999 May 14, 1445(2), 196 - 206 Identification of a cis-acting regulatory sequence responsible for the repression of brnQ in Salmonella typhimurium; Ohnishi K et al.; brnQ is the gene encoding the LIV-II transport system for branched-chain amino acids in Salmonella typhimurium . The expression of the gene is transcriptionally repressed by an excess of glycyl-l-leucine added to the bacterial culture . To investigate the mechanism of regulation, we constructed brnQ-lacZ translational fusions with various deletions upstream from the promoter of brnQ, and examined the effects of the deletions on the regulation . We found a cis-acting region, 5'-GTGTTTTA-3', for the repression of brnQ expression, which was located 94 base pairs upstream from the transcription start site . Removal of the sequence resulted in derepression of brnQ . Two homologous sequences were found 45 base pairs downstream and 42 base pairs upstream from the sequence . We designated these sequences as O1, O2, and O3, in the order from the sequence proximal to the promoter to that distal to the promoter, respectively . The gleR1 mutation, which we reported previously to be a regulatory mutation enhancing transcription of brnQ, was a G-to-T transversion in the O1 sequence 50 base pairs upstream from the transcription start site . Insertion of five nucleotides between O1 and O2 resulted in derepression of brnQ . Further insertion of five nucleotides did not restore the original regulation of brnQ, indicating the importance of the proper spacing of these sequences . We also showed that the protein product of livS, the gene responsible for regulation of the LIV-I transport system, may bind to the O2 sequence . Furthermore, LivS was shown to be an allele of Lrp based on complementation experiments. Parasite Immunol, 1999 Apr, 21(4), 219 - 24 Immunogenicity of the extracellular copper/zinc superoxide dismutase of the filarial parasite Acanthocheilonema viteae delivered by a two-phase vaccine strain of Salmonella typhimurium; Lattemann CT et al.; The recombinant extracellular copper/zinc superoxide dismutase of the filarial parasite Acanthocheilonema viteae (AVSOD2) was cloned in an expression vector under control of the bacteriophage T7 promoter and the resulting plasmid pLAT7 was introduced in tha aroA attenuated Salmonella typhimurium vaccine strain SL3261:pYZ84 . This vaccine strain carries a chromosomally integrated two phase expression system containing inducible T7 RNA polymerase . The recombinant AVSOD2 was efficiently expressed, constituting up to 5% of the total bacterial protein . Furthermore, the plasmid vector containing the AVSOD2 cDNA was shown to be stable over a long period of time in the vaccine strain without antibiotic selection in vitro and in vivo . Jirds which were immunised orally with the recombinant vaccine strain expressing the A . viteae EC-SOD produced a strong humoral immune response. Mol Microbiol, 1999 May, 32(3), 595 - 606 Phage Mu transposition immunity reflects supercoil domain structure of the chromosome; Manna D et al.; Transposition immunity is the negative influence that the presence of one transposon sequence has on the probability of a second identical element inserting in the same site or in sites nearby . A transposition-defective Mu derivative (MudJr1) produced transposition immunity in both directions from one insertion point in the Salmonella typhimurium chromosome . To control for the sequence preference of Mu transposition proteins, Tn10 elements were introduced as targets at various distances from an immunity-conferring MudJr1 element . Mu transposition into a Tn10 target was not detectable when the distance of separation from MudJr1 was 5 kb, and transposition was unencumbered when the separation was 25 kb . Between 5 kb and 25 kb, immunity decayed gradually with distance . Immunity decayed more sharply in a gyrase mutant than in a wild-type strain . We propose that Mu transposition immunity senses the domain structure of bacterial chromosomes. Science, 1999 May 7, 284(5416), 967 - 70 An essential role for DNA adenine methylation in bacterial virulence; Heithoff DM et al.; Salmonella typhimurium lacking DNA adenine methylase (Dam) were fully proficient in colonization of mucosal sites but showed severe defects in colonization of deeper tissue sites . These Dam- mutants were totally avirulent and were effective as live vaccines against murine typhoid fever . Dam regulated the expression of at least 20 genes known to be induced during infection; a subset of these genes are among those activated by the PhoP global virulence regulator . PhoP, in turn, affected Dam methylation at specific genomic sites, as evidenced by alterations in DNA methylation patterns . Dam inhibitors are likely to have broad antimicrobial action, and Dam- derivatives of these pathogens may serve as live attenuated vaccines. Res Rep Health Eff Inst, 1999 Mar, (84), i - iv, 1-22; discussion 23-7 Evaluation of the potential health effects of the atmospheric reaction products of polycyclic aromatic hydrocarbons; Grosovsky AJ et al.; The genotoxic risks from exposure to polycyclic aromatic hydrocarbons (PAHs) have long been recognized . Less well understood are the potential genotoxic risks of the atmospheric reaction products of this class of compounds . In this investigation, we have utilized several human cell assays to evaluate the genotoxicity of naphthalene, phenanthrene, and their atmospheric reaction products 1-nitronaphthalene, 2-nitronaphthalene (2NN), 1-hydroxy-2NN, 2-hydroxy-1-nitronaphthalene, 1,4-naphthoquinone, and 2-nitrodibenzopyranone (2NDBP) . In addition, simulated atmospheric reaction products of naphthalene were generated in a 6,700 liter (L) Teflon environmental chamber, collected on a solid adsorbent, extracted, and fractionated by normal-phase high-performance liquid chromatography (HPLC) . Individual fractions were then analyzed using gas chromatography/mass spectrometry (GC/MS), and tested for genotoxic effects . Genotoxicity was primarily determined using the human B-lymphoblastoid cell line, MCL-5, which expresses several transfected P450 and epoxide hydrolase genes . Mutagenicity was evaluated at both the heterozygous thymidine kinase (tk) locus and the hemizygous hypoxanthine phosphoribosyl transferase (hprt) locus, permitting detection of both intragenic and chromosomal scale mutational events . Test compounds were also screened using the CREST modified micronucleus assay . The results indicate that 2NN and 2NDBP possess greater mutagenic potency than their parent compounds, and, interestingly, both compounds induced significant increases in mutation frequency at the tk but not the hprt locus . These findings suggest a mechanistic difference in human cell response to 2NN and 2NDBP as compared to bacteria, where both compounds were previously shown to induce point mutations in the Salmonella typhimurium reversion assay . The genotoxicity of 2NN and 2NDBP in human cells, together with their high concentrations in ambient air relative to nitro-PAHs directly emitted from combustion sources, emphasizes the need to consider atmospheric reaction products of PAHs in assessments of the genotoxicity of air pollutants . We also investigated whether transfected cytochrome P450 monooxygenase activities were required to activate 2NN and 2NDBP to genotoxic species, and whether a single enzyme could be sufficient for metabolic activation . Three directly related cell lines with multiple (MCL-5), single (AHH-1 1A1), or no (L3) transfected cytochrome P450 genes were used . AHH-1 is additionally distinguished by elevated mutagenic response at the tk locus, a heterozygous mutation in p53, and apoptosis capacity . The effect of these metabolic and genetic differences on genotoxicity of 2NN, 2NDBP, and beta-naphthylamine (beta NA) was also investigated . The results indicated that 2NN and 2NDBP were not activated to genotoxic species through nitroreduction pathways . Mutagenicity induced at the tk locus was dependent on oxidative metabolism, provided by transfected cytochrome P450 enzymes in MCL-5 and AHH-1 1A1 . Mutagenicity was not observed in the L3 cell line, which does not carry transfected cytochrome P450 activities . The negative response of beta NA in all cell lines indicates that, contrary to previous hypotheses, 2NN and beta NA are not activated by similar metabolic pathways in these human cell lines . Taken as a whole, these results suggest that the genotoxicity of nitro-PAHs in human cells requires oxidative metabolism. Arch Pharm Res, 1994 Apr, 17(2), 71 - 5 Antimutagenic effect of plant flavonoids in the Salmonella assay system; Choi JS et al.; The antimutagenic effects of 27 kinds of plant flavonoids on the mutagenicity of aflatoxin B1(AFB1) and N-methyl-N'-nitro-N-nitrosoguanidine(MNNG) in Salmonella typhimurium TA100 were investigated . In the mixed applications of AFB1 (1 microgram/plate) with the flavonoids (300 micrograms/plate) in the presence of a mammalian metabolic activation system (S9 mix), chrysin, apigenin, luteolin and its glucoside, kaempferol, fisetin, morin, naringenin, hesperetin, persicogenin, (+)-catechin and (-)-epicatechin showed the antimutagenic effect against AFB1 with more than 70% inhibition rate . A little or no antimutagenicities except flavone against MNNG (0.5 microgram/plate) were observed . For the antimutagenicity of the flavonoids on AFB1, the flavonoid structure that contains the free 5-, 7-hydroxyl group seemed to be essential . However, saturation of the 2,3-double bond or elimination of the 4-keto group did not affect the activity. Mol Microbiol, 1999 Apr, 32(2), 275 - 87 The genetic basis of tetrathionate respiration in Salmonella typhimurium; Hensel M et al.; A range of bacteria are able to use tetrathionate as a terminal respiratory electron acceptor . Here we report the identification and characterization of the ttrRSBCA locus required for tetrathionate respiration in Salmonella typhimurium LT2a . The ttr genes are located within Salmonella pathogenicity island 2 at centisome 30.5 . ttrA, ttrB and ttrC are the tetrathionate reductase structural genes . Sequence analysis suggests that TtrA contains a molybdopterin guanine dinucleotide cofactor and a {4Fe-4S} cluster, that TtrB binds four {4Fe-4S} clusters, and that TtrC is an integral membrane protein containing a quinol oxidation site . TtrA and TtrB are predicted to be anchored by TtrC to the periplasmic face of the cytoplasmic membrane implying a periplasmic site for tetrathionate reduction . It is inferred that the tetrathionate reductase, together with thiosulphate and polysulphide reductases, make up a previously unrecognized class of molybdopterin-dependent enzymes that carry out the reductive cleavage of sulphur-sulphur bonds . Cys-256 in TtrA is proposed to be the amino acid ligand to the molybdopterin cofactor . TtrS and TtrR are the sensor and response regulator components of a two-component regulatory system that is absolutely required for transcription of the ttrBCA operon . Expression of an active tetrathionate reduction system also requires the anoxia-responsive global transcriptional regulator Fnr . The ttrRSBCA gene cluster confers on Escherichia coli the ability to respire with tetrathionate as electron acceptor. Mol Microbiol, 1999 Apr, 32(2), 243 - 52 Negative and positive regulation of the non-osmoregulated ompS1 porin gene in Salmonella typhi: a novel regulatory mechanism that involves OmpR; Oropeza R et al.; The Salmonella typhi ompS1 gene codes for an outer membrane protein of the OmpC/OmpF porin family . It is expressed at very low levels, relative to the major porins . However, deletion analysis of the 5' regulatory region showed that the gradual removal of nucleotides -310 to -88, upstream from the P1 major transcriptional start-point, resulted in a stepwise increase in expression, reaching levels 10-fold above those for the ompC major porin gene . Hence, this 222 bp segment contains cis-acting regulatory elements involved in negative control . Primer extension analysis revealed the presence of three promoters: P1 activity was OmpR dependent; P2 was expressed at a lower level in the absence of OmpR; and P3 had a minor constitutive activity . OmpR bound preferentially to box II, an 18 bp F1/C1 canonical site, the removal (-88 to -66) of which resulted in a decrease in expression thus supporting its role in positive control . Expression of ompS1 was not induced by a set of stress conditions, including a shift in osmolarity, nor was the IHF regulator involved in negative control . An ompS1 homologue was found in E . coli K-12, which contains a nonsense codon and a shift in the reading frame, whereas Salmonella typhimurium contains an open reading frame in this region . Thus, S . typhi ompS1 provides novel features in OmpR regulation. Poult Sci, 1999 Apr, 78(4), 546 - 9 Effects of chicken-derived cecal microorganisms maintained in continuous culture on cecal colonization by Salmonella typhimurium in turkey poults; Hollister AG et al.; A characterized, chicken-derived, competitive exclusion culture of cecal bacteria was evaluated for effectiveness in the reduction of Salmonella typhimurium cecal colonization in growing turkey poults . The culture was administered by crop gavage on the day of hatch . All groups were challenged orally on Day 3 with 10(4) S . typhimurium . Compared with untreated controls, the percentage of poults that were Salmonella cecal-culture-positive at 10 d of age was significantly reduced (P < 0.05) in the poults provided culture . Additionally, the culture-treated poults had significantly (P < 0.05) fewer Salmonella per gram of cecal contents than the controls . The results indicated that treatment of turkey poults with the characterized chicken-derived culture effectively decreased Salmonella cecal colonization. Chemosphere, 1999 Jun, 38(13), 3015 - 30 Frontier orbital energies, hydrophobicity and steric factors as physical QSAR descriptors of molecular mutagenicity . A review with a case study: MX compounds; Tuppurainen K; A review on QSARs (Quantitative Structure-Activity Relationships) in modelling molecular mutagenicity is given . The importance of hydrophobicity, frontier orbital (HOMO and LUMO) energies and steric factors as physical descriptors of mutagenicity is emphasized . In addition, some possible connections between QSAR models and the general electrophilic theory of genotoxic activity are discussed . As a detailed example, QSARs for the Ames Salmonella typhimurium TA100 mutagenicity of halogenated hydroxyfuranones including MX, one of the most potent bacterial mutagens ever identified, are discussed and a plausible mechanism for their mutagenic activity is proposed. Mutagenesis, 1999 Mar, 14(2), 181 - 5 Microsomal metabolism of dictamnine: identification of metabolites and evaluation of their mutagenicity in Salmonella typhimurium; Klier B et al.; Incubation of the furoquinoline alkaloid dictamnine with microsomal fractions from phenobarbital-induced rat liver resulted in a metabolite mixture from which demethyl-dictamnine and dictamnic acid were identified by a GCMS technique . The identity of the two compounds was confirmed by synthesis . Other metabolites were characterized by their mass spectra only . The pattern of the metabolites suggested a possible pathway of metabolism in vitro . We assume that the metabolism of dictamnine is analogous to the metabolism of the related 8-methoxypsoralen and takes place via an unstable epoxide and subsequent oxidative opening of the furan ring . Direct evidence for the formation of an epoxide was, however, not obtained . The identified compounds as well as some putative metabolites were shown to be non-mutagenic in Salmonella typhimurium TA98 except for 8-hydroxydictamnine, which, however, was not detected in the metabolite mixture. J Immunol, 1999 May 1, 162(9), 5398 - 406 T cell responses to Gram-negative intracellular bacterial pathogens: a role for CD8+ T cells in immunity to Salmonella infection and the involvement of MHC class Ib molecules; Lo WF et al.; Despite being a major group of intracellular pathogens, the role of class I-restricted T cells in the clearance of Gram-negative bacteria is not resolved . Using a murine typhoid model, a role for class I-restricted T cells in the immune response to the Gram-negative pathogen Salmonella typhimurium is revealed . Class I-deficient beta2-microglobulin-/- mice show increased susceptibility to infection with S . typhimurium . Following infection, CD8+ CTLs specific for Salmonella-infected targets can be readily detected . The Salmonella-specific CTLs recognize infected H-2-mismatched targets, suggesting the involvement of shared class Ib molecules . Studies using transfectants expressing defined class Ia and class Ib molecules indicate the involvement of the class Ib molecule, Qa-1 . Ab-blocking studies and the measurement of bacteria-specific CTL frequencies identified Qa-1 as a dominant restricting element . The Qa-1-restricted CTL recognition depends on TAP and proteasome functions . Surprisingly, Qa-1-restricted CTLs recognized cells infected with other closely related Gram-negative bacteria . Taken together, these observations indicate that Salmonella-specific CTLs recognize a cross-reactive epitope presented by Qa-1 molecules and, as such, may be novel targets for vaccine development. Food Chem Toxicol, 1999 Feb-Mar, 37(2-3), 135 - 44 Chemical composition and toxicity of Taiwanese betel quid extract; Wang CK et al.; In this genotoxic study, the Ames Salmonella microsome test showed that an aqueous extract of betel quid did not induce mutagenicity in Salmonella typhimurium strains TA98 and TA100 . Mammalian cell studies (Chinese hamster ovary K1 cell; CHO-K1 cell) revealed that only higher concentrations (100 and 1000 microg/ml) of aqueous extract weekly increased the frequencies of sister-chromatid exchange (SCE) in the absence of S9 . Animal (male Sprague-Dawley rat) studies showed that low-dose feeding (0.53 g dry aqueous extract/kg diet) significantly increased the activities of glutathione (GSH) peroxidase and cytoplasmic glutathione S-transferase (cGST) of liver, high-dose feeding (26.5 g dry aqueous extract/kg diet) lowered the contents of GSH and total glutathione . The effect of an aqueous extract of betel quid on the oxidation of 2'-deoxyguanosine (2'-dG) to 8-hydroxy-2'-deoxyguanosine (8-OH-dG) evaluated that this aqueous extract may act as a pro-oxidant at lower dosage and may be dependent on the iron ions in the model system . However, the aqueous extract of betel quid showed antioxidant activity at higher doses by the ability of the scavenging effect of the hydroxyl radicals. Food Chem Toxicol, 1999 Feb-Mar, 37(2-3), 95 - 103 Antimutagens in food plants eaten by Polynesians: micronutrients, phytochemicals and protection against bacterial mutagenicity of the heterocyclic amine 2-amino-3-methylimidazo{4,5-f}quinoline; Botting KJ et al.; We have previously suggested that differences in cancer incidence between Polynesians (including Maoris and people from several Pacific islands) and Europeans in New Zealand may at least partially relate to differences in the species of food plants (fruits, vegetables and cereals) preferentially eaten by these groups . Twenty-five food plants that are typically eaten in different amounts by these two population groups were selected for detailed study . Antimutagenic properties of three extracts from each of the selected plants were investigated using a preincubation mutagenicity assay with Salmonella typhimurium strain TA1538 against the mutagenicity of the heterocyclic amine 2-amino-3-methylimidazo{4,5-f}quinoline (IQ) . The data revealed strong antimutagenic properties in several of the food plants commonly eaten by Polynesians, especially rice, watercress, pawpaw, taro leaves, green banana and mango . Using the New Zealand food database, a number of nutrients and micronutrients with antimutagenic and anticarcinogenic potential were identified from the selected food plants . Some of these were tested for antimutagenic potential in parallel experiments to those done with the food plant extracts . Although some of these micronutrients are antimutagens against IQ, their concentrations in the food plants failed to explain the protection against mutagenicity found in the experiments with extracts of the food plants . Thus, other types of chemical, not identified in the database, must be leading to antimutagenesis . Possible active molecules include chlorophylls, carotenoids, flavonoids and coumarins, many of which are also known to be anticarcinogens . If human cancer data are to be interpreted in terms of cancer protection, these components need urgently to be quantified in food plants in the New Zealand diet, especially in those food plants eaten in large amounts by Polynesians. FEMS Microbiol Lett, 1999 Apr 15, 173(2), 411 - 23 Sample sequencing of a Salmonella typhimurium LT2 lambda library: comparison to the Escherichia coli K12 genome; Wong RM et al.; As part of the ongoing sequencing of the complete Salmonella typhimurium LT2 genome, a partly ordered set of 416 lambda clones has been developed, representing over 90% of the genome . The average insert size is 17 kb . Sequences were obtained from both ends of each clone in this set . A total of over 600 kb of sequence has been deposited in the genome survey sequence section of GenBank . This resource of clones is available from the Salmonella Genome Stock Center . A preliminary comparison with the Escherichia coli K12 genome indicates that there are likely to be many hundred insertion deletion events, encompassing more than one gene, that distinguish these genomes . Fully 30% of the S . typhimurium sequences have no close homologs in the GenBank database. Biosci Biotechnol Biochem, 1999 Mar, 63(3), 537 - 41 Antimutagenicity of sweetpotato (Ipomoea batatas) roots; Yoshimoto M et al.; Antimutagenicity of the water extracts prepared from the storage roots of four varieties of sweetpotato with different flesh colors was investigated using Salmonella typhimurium TA 98 . The extract from the whole roots of the purple-colored Ayamurasaki variety effectively decreased the reverse mutation induced not only by Trp-P-1, Trp-P-2, IQ, B{a}P, and 4-NQO but also by dimethyl sulfoxide extracts of grilled beef . Comparison of the inhibitory activity of the extracts from the normal Ayamurasaki and its anthocyanin-deficient mutant one suggested that the anthocyanin pigment in the flesh decreases the mutagenic activity of the mutagens as heterocyclic amines . Two anthocyanin pigments purified from purple-colored sweet-potato, 3-(6,6'-caffeylferulylsophoroside)-5-glucoside of cyanidin (YGM-3) and peonidin (YGM-6) effectively inhibited the reverse mutation induced by heterocyclic amines, Trp-P-1, Trp-P-2, and IQ in the presence of rat liver microsomal activation systems. Anticancer Res, 1999 Jan-Feb, 19(1A), 569 - 72 Antimutagenicity of lignin in vitro; Ebringer L et al.; The inhibitory activity of lignin against nitrosoguanidine (MNNG)- and acridine orange (AO)- induced mutagenesis was examined using two microbial systems: green unicellular flagellate Euglena gracilis and Salmonella typhimurium TA100 and TA97 . To verify the hypothesis that the above mentioned mutagens may generate some oxidant species and subsequently free radicals, or they may interact with lignin, two physico-chemical measurements were performed . Lignin at a tested concentration (100 micrograms/ml) decreases Euglena-bleaching activity of MNNG by 67.7% and AO by 99.7% . Percentage of MNNG-induced revertants of S . typhimurium was also decreased substantially by lignin . We conclude that our results indicate the possible mechanisms behind the antimutagenic/anticarcinogenic effects of lignin: namely, scavening of reactive oxygen species produced by MNNG and binding of AO itself. Infect Immun, 1999 May, 67(5), 2292 - 8 Characterization of the Escherichia coli AF/R1 pilus operon: novel genes necessary for transcriptional regulation and for pilus-mediated adherence; Cantey JR et al.; We isolated the genetic determinant of AF/R1 pilus production in attaching/effacing Escherichia coli RDEC-1 and identified seven genes required for pilus expression and function . DNA sequence analysis of the structural subunit gene afrA corrected an error in the published sequence and extended homology with the F18 pilus subunit of pig edema E . coli strains . AfrB and AfrC, encoded downstream from AfrA, were required for pilus expression . AfrB was related to the usher protein PefC of Salmonella typhimurium plasmid-encoded fimbriae, and AfrC was related to PefD, a chaperone protein . AfrD and AfrE, encoded downstream from AfrC, were not necessary for the expression of AF/R1 pili but were required for ileal adherence as assayed by ileal brush border aggregation . Thus, the adhesive subunit of the AF/R1 pilus is distinct from the structural subunit, as is the case for Pap pili and type 1 pili . AfrD was related to FedE of the F18 fimbrial operon of the E . coli strain that causes edema disease in pigs . AfrE was a novel protein . AfrR and AfrS are encoded upstream from AfrA, in the opposite orientation . AfrR is related to the AraC family of transcriptional regulators, and AfrR and AfrS interact to function in a novel mode of transcriptional activation of afrA . AF/R1 pili mediate the adherence to Peyer's patch M cells, ileal mucosa, and colonic mucosa in a rabbit model of diarrhea caused by enteropathogenic E . coli . Our observations will facilitate the further study of the phenomena of M-cell adherence. Infect Immun, 1999 May, 67(5), 2225 - 32 Functional expression of Nramp1 in vitro in the murine macrophage line RAW264.7; Govoni G et al.; Mutations at the Nramp1 locus in vivo cause susceptibility to infection by unrelated intracellular microbes . Nramp1 encodes an integral membrane protein abundantly expressed in the endosomal-lysosomal compartment of macrophages and is recruited to the phagosomal membrane following phagocytosis . The mechanism by which Nramp1 affects the biochemical properties of the phagosome to control microbial replication is unknown . To devise an in vitro assay for Nramp1 function, we introduced a wild-type Nramp1(G169) cDNA into RAW 264.7 macrophages (which bear a homozygous mutant Nramp1(D169) allele and thus are permissive to replication of specific intracellular parasites) . Recombinant Nramp1 was expressed in a membranous compartment in RAW264.7 cells and was recruited to the membrane of Salmonella typhimurium and Yersinia enterocolitica containing phagosomes . Evaluation of the antibacterial activity of RAW264.7 transfectants showed that expression of the recombinant Nramp1 protein abrogated intracellular replication of S . typhimurium . Studies with a replication-defective S . typhimurium mutant suggest that this occurs through an enhanced bacteriostatic activity . The effect of Nramp1 expression was specific, since (i) it was not seen in RAW264.7 transfectants overexpressing the closely related Nramp2 protein, and (ii) control RAW264.7 cells, Nramp1, and Nramp2 transfectants could all efficiently kill a temperature-sensitive, replication-defective mutant of S . typhimurium . Finally, increased antibacterial activity of the Nramp1 RAW264.7 transfectants was linked to increased phagosomal acidification, a distinguishing feature of primary macrophages expressing a wild-type Nramp1 allele . Together, these results indicate that transfection of Nramp1 cDNAs in the RAW264.7 macrophage cell line can be used as a direct assay to study both Nramp1 function and mechanism of action as well as to identify structure-function relationships in this protein. Virus Res, 1999 Mar, 60(1), 95 - 9 Specific interaction of fused H protein of bacteriophage phiX174 with receptor lipopolysaccharides; Suzuki R et al.; The DNA fragment encoding the spike H protein of bacteriophage phiX174 was amplified by polymerase chain reaction . The fragment was sub-cloned into pQE-30 to yield pQE-H . The histidine-tagged H protein (HisH) was obtained from the cell extract of Escherichia coli M15 (pREP4) harboring pQE-H and purified by nickel chelating and anion-exchange chromatographies . HisH was shown to bind dose-dependently to the lipopolysaccharides (LPSs) isolated from phiX174-sensitive strains, E . coli C or Salmonella typhimurium TV119 (Ra mutant) . In sharp contrast, HisH did not bind to the LPSs from insensitive strains, E . coli F583 (Rd2 mutant) or E . coli O111:B4 (smooth strain) . Since the same selectivity was observed in the plaque counting assay for in vitro inactivation of phiX174, the spike H protein was shown to recognize receptor LPS. Kaohsiung J Med Sci, 1999 Mar, 15(3), 127 - 36 Epidemiological study of human salmonellosis during 1991-1996 in southern Taiwan; Chen YH et al.; Within a 6-year period from January 1991 to December 1996, 249 patients of salmonellosis admitted to Kaohsiung Medical College Hospital were enrolled for clinical and microbiological analysis . The number of patients increased by year from 1991 (14 patients) to 1996 (79 patients), especially in the case of nontyphoid salmonellosis . There were 57 different serotypes isolated during these period . Salmonella typhimurium was the most common clinical serotype of human origin in southern Taiwan, followed by S . choleraesuis, S . schwanzengrund, and S . derby . Fever (81.1%), diarrhea (68.9%), and anorexia (44.6%) were the most common manifestations of human salmonellosis . Relative bradycardia was a more important feature in S . typhi group (100%) than nontyphoid salmonellosis . Leukocytosis, especially lymphocytosis, was found especially in nontyphoid, but not in typhoid salmonellosis . Elevated liver function tests were found in the most severe patients, such as S . choleraesuis and S . typhi infections . Malignancy (8.8%), especially hematological malignancy (5.2%), gastrointestinal diseases (8.8%), and diabetes mellitus (6.4%) were the common underlying diseases . Case fatality rate of human salmonellosis was 8% (20/249), especially high in S . choleraesuis group . The severity of underlying diseases may be the major cause in S . choleraesuis group . There was no fatal case with typhoid fever . Very high resistance rate to commonly used antimicrobial agents in nontyphoid Salmonella was noted in southern Taiwan with overall rates of resistance to ampicillin, 67.9%, chloramphenicol, 66.7%, and TMP/SMZ, 42.2% . The emergence of ciprofloxacin-resistant and multiresistant strains was also a major therapeutic problem in this study. Mutat Res, 1999 Apr 26, 441(1), 43 - 51 Exposure to mutagenic airborne particulate in a rubber manufacturing plant; Fracasso ME et al.; Epidemiological studies conducted in the 1980s revealed that people working in the rubber manufacturing industry had an increased risk of cancer . Even now, workers employed in rubber processing are still at risk despite the measures adopted to improve their working conditions . The aim of the study was to evaluate the presence of a genotoxic risk in a rubber industry and to verify whether or not it was possible to locate the most dangerous position among the different rubber-working processes . The mutagenic activity of airborne particulate was evaluated in samples collected in the mixing department of a rubber manufacturing plant . Ambient air samples were taken over 3-h period in two stable positions near the mixing (Banbury mixer) and calendering areas . Personal air samples were taken over 2-h period during a normal workday from five workers employed in different rubber processing operations (mixing, weighing, calendering, compounding and extruding) . The mutagenic activity of the air samples was determined by plate incorporation assay using Salmonella typhimurium strains (TA 98, TA 98NR, TA 100, YG 1021) with and without metabolic activation . Polycyclic aromatic hydrocarbon (PAH) concentrations were determined by high-performance liquid chromatography (HPLC); the presence of other presumable contaminants were carried out by gas chromatography-mass spectrometry (GC-MS) . The results showed substantial direct and indirect frameshift mutagenicity in both ambient and personal samples . No mutagenic activity was present in S . typhimurium TA 100, except in the personal sample from a worker employed on the Banbury mixer . HPLC analysis revealed very low concentrations of PAHs . GC-MS analysis showed the presence of compounds such as azulene derivative, 1,2-dihydro-2,2,4-trimethylquinoline, N-methyl N-phenylbenzenamine, diphenylamine, bis(2-ethylhexyl)phthalate and bis(methyl-propyl)phthalate . We conclude that the high levels of mutagenic activity in ambiental and personal samples indicate the presence of substances with high genotoxic potency; no substantial differences were seen among the several rubber processing operations . PAHs were not involved in indoor pollution . GC-MS analysis revealed the presence of compounds which may be produced by high temperatures to which the raw materials are subjected during rubber manufacturing processes . These substances are potential carcinogen though their mutagen properties have not been clearly determined . Mutat Res, 1999 Apr 26, 441(1), 1 - 9 Antimutagenic effects of natural phenolic compounds in beans; de Mejia EG et al.; Polyphenols in fruits, vegetables (e.g., flavonols like quercetin) and tea (e.g., catechins such as epigallocatechin gallate) are good antioxidants with antimutagenic and anticarcinogenic properties . In the present study, the Salmonella typhimurium tester strain YG1024 was used in the plate-incorporation test to examine the antimutagenic effect of phenolic compounds, extracted from common beans (Phaseolus vulgaris), on 1-NP and B{a}P mutagenicity . Dose-response curves for 1-NP and B{a}P were obtained; the number of net revertants/plate at the peak mutagenic dosage were 880 for 1-NP and 490 for B{a}P . For the antimutagenicity studies doses of 0.1 microg/plate and 2 microg/plate for 1-NP and B{a}P, respectively, were chosen . We obtained a dose-response curve of ellagic acid (EA) against B{a}P and 1-NP mutagenicity . To test the bean extract, a dose of 300 microg/plate of EA was chosen as the antimutagenic control . The EA and bean extracts were not toxic to the bacteria at the concentrations tested . The inhibitory effects of the bean extracts and EA against B{a}P mutagenicity were dose-dependent . The percentages of inhibition produced against B{a}P (2 microg/plate) using 300 microg/plate of EA and for the extracts 500 microg equivalent catechin/plate were 82%, 83%, 81% and 83% for EA, water extract, water/methanol extract and methanol extract, respectively . However, for 1-NP mutagenicity, only the methanolic extract from beans showed an inhibitory effect . These results suggest that common beans, as other legumes, can function as health-promoting foods . J Exp Med, 1999 May 3, 189(9), 1479 - 88 Requirement of p21-activated kinase (PAK) for Salmonella typhimurium-induced nuclear responses; Chen LM et al.; Salmonella typhimurium has sustained a long-standing association with its host and therefore has evolved sophisticated strategies to multiply and survive within this environment . Central to Salmonella pathogenesis is the function of a dedicated type III secretion system that delivers bacterial effector proteins into the host cell cytoplasm . These effectors stimulate nuclear responses and actin cytoskeleton reorganization leading to the production of proinflammatory cytokines and bacterial internalization . The stimulation of these responses requires the function of Cdc42, a member of the Rho family of small molecular weight GTPases, and SopE, a bacterial effector protein that stimulates guanine nucleotide exchange on Rho GTPases . However, nothing is known about the role of Cdc42 effector proteins in S . typhimurium-induced responses . We showed here that S . typhimurium infection of cultured epithelial cells results in the activation of p21-activated kinase (PAK), a serine/threonine kinase that is an effector of Cdc42-dependent responses . Transient expression of a kinase-defective PAK blocked both S . typhimurium- and SopE-induced c-Jun NH2-terminal kinase (JNK) activation but did not interfere with bacteria-induced actin cytoskeleton rearrangements . Similarly, expression of SH3-binding mutants of PAK did not block actin-mediated S . typhimurium entry into cultured cells . However, expression of an effector loop mutant of Cdc42Hs (Cdc42HsC40) unable to bind PAK and other CRIB (for Cdc42/Rac interacting binding)-containing target proteins resulted in abrogation of both S . typhimurium-induced nuclear and cytoskeletal responses . These results show that PAK kinase activity is required for bacteria-induced nuclear responses but it is not required for cytoskeletal rearrangements, indicating that S . typhimurium stimulates cellular responses through different Cdc42 downstream effector activities . In addition, these results demonstrate that the effector loop of Cdc42 implicated in the binding of PAK and other CRIB-containing target proteins is required for both responses. Appl Environ Microbiol, 1999 May, 65(5), 1924 - 9 Combinations of intervention treatments resulting in 5-log10-unit reductions in numbers of Escherichia coli O157:H7 and Salmonella typhimurium DT104 organisms in apple cider; Uljas HE et al.; The U.S . Food and Drug Administration (FDA) recently mandated a warning statement on packaged fruit juices not treated to reduce target pathogen populations by 5 log10 units . This study describes combinations of intervention treatments that reduced concentrations of mixtures of Escherichia coli O157:H7 (strains ATCC 43895, C7927, and USDA-FSIS-380-94) or Salmonella typhimurium DT104 (DT104b, U302, and DT104) by 5 log10 units in apple cider with a pH of 3.3, 3.7, and 4.1 . Treatments used were short-term storage at 4, 25, or 35 degrees C and/or freeze-thawing (48 h at -20 degrees C; 4 h at 4 degrees C) of cider with or without added organic acids (0.1% lactic acid, sorbic acid {SA}, or propionic acid) . Treatments more severe than those for S . typhimurium DT104 were always required to destroy E . coli O157:H7 . In pH 3.3 apple cider, a 5-log10-unit reduction in E . coli O157:H7 cell numbers was achieved by freeze-thawing or 6-h 35 degrees C treatments . In pH 3.7 cider the 5-log10-unit reduction followed freeze-thawing combined with either 6 h at 4 degrees C, 2 h at 25 degrees C, or 1 h at 35 degrees C or 6 h at 35 degrees C alone . A 5-log10-unit reduction occurred in pH 4.1 cider after the following treatments: 6 h at 35 degrees C plus freeze-thawing, SA plus 12 h at 25 degrees C plus freeze-thawing, SA plus 6 h at 35 degrees C, and SA plus 4 h at 35 degrees C plus freeze-thawing . Yeast and mold counts did not increase significantly (P < 0.05) during the 6-h storage at 35 degrees C . Cider with no added organic acids treated with either 6 h at 35 degrees C, freeze-thawing or their combination was always preferred by consumers over pasteurized cider (P < 0.05) . The simple, inexpensive intervention treatments described in the present work could produce safe apple cider without pasteurization and would not require the FDA-mandated warning statement. APMIS, 1999 Mar, 107(3), 318 - 24 The effect of hydrocarbon chain length, pH, and temperature on the binding and bactericidal effect of amphiphilic betaine esters on Salmonella typhimurium; Ahlstrom B et al.; Amphiphilic betaine esters are quaternary ammonium compounds (QAC) with rapid microbicidal action . They are often labeled 'soft antimicrobial agents', since the compounds hydrolyze spontaneously into betaine and fatty alcohols, thus not only losing their surface active properties and toxicity but also becoming amenable to metabolic use . The present results show that the bactericidal effects of 1-decyl (B10), 1-dodecyl (B12), and 1-tetradecyl (B14) betaine esters on Salmonella typhimurium 395 MS decreased with decreasing hydrocarbon chain lengths, decreased at pH below neutral, and were lower at 0 degrees C that at 30 degrees C . At least part of the decreased effect at pH 4.0 as compared to pH 6.0 can be explained by reduced binding . However, reduced binding cannot explain the decrease in the microbicidal effect at 0 degrees C since the binding of B 14 was the same at 0 degrees C and 30 degrees C although 10-30 times higher concentrations were required at 0 degrees C to achieve the same microbicidal effect as at 30 degrees C . Neither can differences in binding explain the great differences seen in microbicidal effect between QAC with different chain lengths . It is proposed that the membrane deformation resulting in killing of S . typhimurium is more efficiently achieved with QAC with longer hydrocarbon chains and that reduced fluidity of the outer membrane of the bacteria at lower temperatures antagonizes the bactericidal effect . Charge interaction seems to be more important for the binding and bactericidal effect for the QAC with shorter hydrocarbon chains . The different effects of pH, temperature, and hydrocarbon chain length on binding, bactericidal effect, and hydrolysis have to be taken into account when optimizing disinfection and the subsequent elimination of disinfectants. Carcinogenesis, 1999 Apr, 20(4), 545 - 51 Heterocyclic aromatic amines induce DNA strand breaks and cell transformation; Pfau W et al.; Heterocyclic aromatic amines (HAAs), formed during the cooking of foods, are known to induce tumours in rodent bioassays and may thus contribute to human cancer risk . We tested six HAAs in a morphological transformation assay and in three in vitro genotoxicity assays . The morphological transforming abilities of HAAs were tested, in the presence of rat-liver S9, in the C3H/M2 fibroblast cell line . Concentration levels of 50 microM 2-amino-3,8-dimethylimidazo{4,5-f}quinoxaline (8-MeIQx), 100 microM 2-amino-3,4,8-trimethylimidazo-{4,5-f}quinoxaline (4,8-DiMeIQx), 50 microM 2-amino-3-methylimidazo{4,5-f}quinoline (IQ), 100 microM 2-amino-9H-pyrido{2,3-b}indole (AalphaC), 100 microM 2-amino-3-methyl-9H-pyrido{2,3-b}indole (MeAalphaC) and 15 microM 2-amino-1-methyl-6-phenylimidazo{4,5-b}pyridine (PhIP) induced maximum transformation potencies of 5.5, 6.6, 6.3, 5.2, 7.3 and 9.2 transformed foci per 10(4) surviving cells, respectively . Bacterial mutagenic activity was determined in the presence of rat-liver S9 using the Salmonella typhimurium reverse-mutation assay employing strain YG1019 . Mutagenic potencies of 3800 revertants (revs)/ng with 8-MeIQx, 2900 revs/ng with 4,8-DiMeIQx, 3480 revs/ng with IQ, 1.6 revs/ng with AalphaC, 2.9 revs/ng with MeAalphaC and 5 revs/ng with PhIP were observed . Clastogenic activity in vitro was analysed by the micronucleus assay in metabolically competent MCL-5 cells . Dose-dependent induction of micronuclei was observed for all HAAs tested with 1-5.4% of cells containing micronuclei at 10 ng/ml . Micronucleus induction was in the order 4,8-DiMeIQx > 8-MeIQx > IQ > MeAalphaC > PhIP > AalphaC . DNA strand-breaking activity in MCL-5 cells was measured by the alkaline single cell-gel (comet) assay . The lowest effect doses for significant increases (P < or = 0.0007, Mann-Whitney test) in comet tail length (microm) were 45.5 microg/ml (200 microM) for PhIP, 90.9 microg/ml (410-510 microM) for 4,8-DiMeIQx, IQ, MeAalphaC and AalphaC, and 454.5 microg/ml (2130 microM) for 8-MeIQx . It is not yet clear which of these assays most accurately reflects the genotoxic potential to humans of compounds of this class of environmental carcinogens. Emerg Infect Dis, 1999 Mar-Apr, 5(2), 216 - 23 Enteropathogenic E . coli, Salmonella, and Shigella: masters of host cell cytoskeletal exploitation; Goosney DL et al.; Bacterial pathogens have evolved numerous strategies to exploit their host's cellular processes so that they can survive and persist . Often, a bacterium must adhere very tightly to the cells and mediate its effects extracellularly, or it must find a way to invade the host's cells and survive intracellularly . In either case, the pathogen hijacks the host's cytoskeleton . The cytoskeleton provides a flexible framework for the cell and is involved in mediating numerous cellular functions, from cell shape and structure to programmed cell death . Altering the host cytoskeleton is crucial for mediating pathogen adherence, invasion, and intracellular locomotion . We highlight recent advances in the pathogenesis of enteropathogenic Escherichia coli, Salmonella Typhimurium, and Shigella flexneri . Each illustrates how bacterial pathogens can exert dramatic effects on the host cytoskeleton. Biochemistry, 1999 Apr 27, 38(17), 5283 - 9 Selection and characterization of human cytochrome P450 1A2 mutants with altered catalytic properties; Parikh A et al.; Random mutagenesis is an approach that has the potential to provide useful information about cytochrome P450 (P450) enzymes but has not been extensively used to date . We applied our previously developed systems for generation of random libraries of human P450 1A2 with the putative substrate recognition sequences mutated (individual residues) and an Escherichia coli genotoxity assay involving reversion to lac prototrophy as a response to activation of the heterocyclic amine 2-amino-3,5-dimethylimidazo{4,5-f}quinoline (MeIQ) . A total of 27 mutants were screened from 6000 clones, a small portion of the library . The sequence changes were identified, and E . coli membranes containing each P450 (with NADPH-P450 reductase expressed using a bicistronic vector) were used to determine kcat and Km values for 7-ethoxyresorufin and phenacetin O-deethylation and the (in vitro) activation of MeIQ with another bacterial genotoxicity system (Salmonella typhimurium umu) . Within each assay, the values of kcat/Km varied by 2 orders of magnitude, and in some cases these parameters were 3-4-fold higher than for the native enzyme . The profiles of the mutants varied considerably for the three different reactions . Some of the mutants in the Asp-320 region may be compared with site-directed mutants of rat P450 1A2 already reported, with several differences noted . Other mutants have not been studied before in human P450 1A2 or homologues and are of interest; i.e., all Phe-226 mutants showed considerably reduced activity but Glu-225 mutants had increased catalytic activities . In principle, this approach may be applied to random mutagenesis of any enzyme that converts chemicals to mutagens and can be expressed in bacteria. Shock, 1999 Apr, 11(4), 253 - 8 Lethality of endotoxin in mice genetically deficient in the respiratory burst oxidase, inducible nitric oxide synthase, or both; Nicholson SC et al.; Two classes of oxidants are thought to play a critical role in tissue damage in septic shock: reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI) . Particular importance has been ascribed to peroxynitrite, a product arising from the reaction of nitric oxide with superoxide . A major source of ROI is the respiratory burst oxidase of neutrophils, eosinophils, monocytes, and macrophages . A major source of RNI is inducible nitric oxide synthase (iNOS), an enzyme expressed in leukocytes, hepatocytes, vascular smooth muscle cells, endothelium, and cardiac myocytes during inflammation . In previous studies using various mouse models of endotoxic shock, genetic deficiency of iNOS as a sole intervention did not consistently alter survival . Here, using Salmonella typhimurium endotoxic bacterial lipopolysaccharide (LPS) as a sole challenge, genetic deficiency of iNOS was associated with no protection or a reduction in survival, depending on the dose of LPS . Further, no protection from lethality was observed when LPS was injected into mice genetically deficient in the 91 kDa subunit of the respiratory burst oxidase (gp91phox) nor in mice genetically deficient in both gp91phox and iNOS (gp91phox-/-/NOS2-/- mice) . For the latter experiments, mice were challenged either with S . typhimurium LPS alone or with inactivated bacille Calmette-Guerin (BCG) followed by Escherichia coli LPS . Deficiency of gp91phox impaired the inflammatory response to inactivated Propionobacterium acnes, rendering survival studies following priming with P . acnes difficult to interpret . Thus, in two models of endotoxic shock, major reductions in the ability to form nitric oxide or superoxide, alone or in combination, failed to improve survival. J Bacteriol, 1999 May, 181(9), 2938 - 41 Histidine operon deattenuation in dnaA mutants of Salmonella typhimurium correlates with a decrease in the gene dosage ratio between tRNA(His) and histidine biosynthetic loci; Blanc-Potard AB et al.; Expression of the histidine operon of Salmonella typhimurium is increased in dnaA(Ts) mutants at 37 degrees C . This effect requires an intact his attenuator and can be suppressed by increasing the gene copy number of the hisR locus, which encodes the tRNA(His) . We present data which suggest that the his deattenuation defect in dnaA(Ts) mutants results from the loss of a gene dosage gradient between the hisR locus, close to oriC, and the his operon, far from oriC . Some of the conclusions drawn here may apply to other operons as well. FEBS Lett, 1999 Apr 1, 448(1), 131 - 4 A Cys-less variant of the bacterial ATP binding cassette protein MalK is functional in maltose transport and regulation; Hunke S et al.; The cysteine residues of the ABC protein MalK from Salmonella typhimurium maltose transport system (C40, C350, C360) were consecutively replaced by serines . Cys-less MalK was fully functional in maltose transport in vivo . Moreover, the activity of MalK as a repressor of other maltose-regulated genes was also retained . The absence of cysteine residues in the purified protein was verified by its failure to react with fluorescein-5-maleimide . In contrast to purified wild-type MalK, the ATPase activity of the C40S variant was insensitive to inhibition by N-ethylmaleimide. Mol Microbiol, 1999 Apr, 32(1), 179 - 91 The regulation and role of the periplasmic copper, zinc superoxide dismutase of Escherichia coli; Gort AS et al.; The discovery of superoxide dismutase (CuZnSOD) within the periplasms of several Gram-negative pathogens suggested that this enzyme evolved to protect cells from exogenous sources of superoxide, such as the oxidative burst of phagocytes . However, its presence in some non-pathogenic bacteria implies that there may be a role for this SOD during normal growth conditions . We found that sodC, the gene that encodes the periplasmic SOD of Escherichia coli, is repressed anaerobically by Fnr and is among the many antioxidant genes that are induced in stationary phase by RpoS . Surprisingly, the entry of wild-type E . coli into stationary phase is accompanied by a several-hour-long period of acute sensitivity to hydrogen peroxide . Induction of the RpoS regulon helps to diminish that sensitivity . While mutants of E . coli and Salmonella typhimurium that lacked CuZnSOD were not detectably sensitive to exogenous superoxide, both were killed more rapidly than their parent strains by exogenous hydrogen peroxide in early stationary phase . This sensitivity required prior growth in air . Evidently, periplasmic superoxide is generated during stationary phase by endogenous metabolism and, if it is not scavenged by CuZnSOD, it causes an unknown lesion that augments or accelerates the damage done by peroxide . The molecular details await elucidation. Biosci Biotechnol Biochem, 1999 Jan, 63(1), 216 - 9 Occurrence of stereoisomers of 1-(2'-pyrrolidinethione-3'-yl)- 1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in fermented radish roots and their different mutagenic properties; Ozawa Y et al.; Stereoisomers of the tetrahydro-beta-carboline derivative, 1-(2-pyrrolidinethione)-3-yl)-1,2,3,4-tetrahydro-beta-carboline- 3-carboxylic acid (PTCC), were formed from L-tryptophan with 4-methylthio-3-butenyl isothiocyanate, and their mutagenic properties and contents in different types of the radish products were studied . The isomers were identified as (1S*, 3S*, 3R*)- and (1R*, 3S*, 3R*)-PTCCs; the former was found as the major compound but had no mutagenic activity, while the latter was mutagenic toward Salmonella typhimurium TA 98 in the presence of a rat microsomal fraction . Both (1S*, 3S*, 3R*)- and (1R*, 3S*, 3R*)-PTCC were detected in a ratio of about 4:1 in a product fermented for 8 months, but only a trace was apparent in products manufactured within a few weeks. Lett Appl Microbiol, 1999 Apr, 28(4), 255 - 7 Induction of rpoS in Salmonella typhimurium by nutrient-poor and depleted media is slower than that achieved by a competitive microflora; Aldsworth TG et al.; The presence of a viable competitive microflora, at greater than 10(8) cfu ml-1, is known to advance the induction of RpoS-mediated gene expression in a sub-population of Salmonella typhimurium . As starvation is known to induce RpoS, one action of the competitive microflora could be to cause depletion of essential nutrients . The aim of the current experiments was to determine whether this was the case by examining RpoS induction in Salm . typhimurium in reduced nutrient media . RpoS-mediated gene expression in Salm . typhimurium was not advanced so significantly in 'conditioned' or diluted medium as it was in the presence of competitors, which indicates that nutrient depletion was not the responsible mechanism . The effect of a competitive microflora has implications for models of bacterial survival during food processing, as RpoS ultimately regulates both stress resistance and virulence. Mol Microbiol, 1999 Mar, 31(6), 1759 - 73 Environmental regulation of Salmonella pathogenicity island 2 gene expression; Deiwick J et al.; The enteric pathogen Salmonella typhimurium co-ordinates the expression of virulence determinants in response to environmental cues from the host organism . S . typhimurium possesses Salmonella pathogenicity island 2 (SPI2), a large virulence locus encoding a type III secretion system for virulence determinants required fo