J Biol Chem, 1991 Jul 5, 266(19), 12741 - 6 The kinetic mechanism of S-adenosyl-L-methionine: glutamylmethyltransferase from Salmonella typhimurium; Simms SA et al.; The kinetic mechanism of the CheR methyltransferase, S-adenosyl-L-methionine (AdoMet): protein-L-glutamate O-methyltransferase (EC 2.1.1.24), from Salmonella typhimurium was investigated . Initial velocity, product inhibition, and binding studies were performed, and from the data obtained, it was determined that the mechanism of the reaction catalyzed by the enzyme is random . Initial velocity rates were measured with varied amounts of both substrates, and double-reciprocal plots gave patterns which converged on or near the abscissa . The products, S-adenosyl-L-homocysteine and methylated receptor, were found to be competitive inhibitors with respect to both AdoMet and receptor . Equilibrium dialysis and immunoprecipitation studies indicated that the two substrates can bind to the enzyme independent of each other . These results are consistent with a random mechanism with no abortive complexes being formed . The Michaelis constants calculated for AdoMet and receptor were 8.62 microM and 2.03 mg/ml total membrane protein (approximately 2.10 microM Tar protein), and the apparent dissociation constants of AdoMet and the receptor were 16.8 microM and 4.07 mg/ml total membrane protein (approximately 4.2 microM Tar protein), respectively . The Kd of AdoMet for the enzyme was 10.9 microM as determined by binding studies. J Med Microbiol, 1991 Jul, 35(1), 53 - 9 Passive secretory immunity against Salmonella typhimurium demonstrated with foster mouse pups; Shope SR et al.; Mice immunised by drinking water containing an Aro- mutant strain of Salmonella typhimurium produced intestinal IgA antibodies after a memory response which was demonstrated by measuring copro-antibodies . After oral challenge with a virulent strain of S . typhimurium, foster mouse pups placed with immunised mothers survived longer than control pups held with non-immunised mothers. Carcinogenesis, 1991 Jul, 12(7), 1221 - 5 Tumor promoting potential in male F344 rats and mutagenicity in Salmonella typhimurium of dipyrone; Izumi K et al.; For assessment of the carcinogenic potential and the mutagenicity of dipyrone, an antipyretic anodyne, -{(2,3-dihydro-1,5-dimethyl-3-oxo-2-phenyl-1H-pyrazol-4-yl) methylamino}-methanesulfonic acid sodium salt monohydrate, three experiments were conducted using dipyrone A produced in Japan and/or dipyrone B obtained from the Federal Republic of Germany . (i) Carcinogenic potential of dipyrone A for rat liver: 8 week old male F344 rats were pretreated with 0.01% diethylnitrosamine (DEN) in drinking water for 2 weeks and, after 1 week of resting, administered 0.4% dipyrone in drinking water, 5 days a week, for 72 weeks . After an 8 week recovery period, all surviving rats were killed at 83 weeks . Hepatocellular carcinomas developed at a higher incidence in the DEN + dipyrone group (18 of 29 rats, 62%) than in the DEN alone group (9 of 29 rats, 31%), the difference being statistically significant (P less than 0.05) . No carcinogenic activity of dipyrone was demonstrated in the groups given 0.4% dipyrone for 72 weeks or 0.4% dipyrone for 25 weeks, followed by 0.05% phenobarbital (PB) for 50 weeks . However, glutathione S-transferase P positive (GST-P+) preneoplastic hepatic foci in these groups were observed at a higher incidence than in the untreated control group (P less than 0.01) . (ii) Effect of dipyrone A and dipyrone B on induction of DEN-initiated GST-P+ hepatic foci in a medium-term bioassay system: 0.4% dipyrone A in drinking water and 0.57% dipyrone A or dipyrone B in powdered diet after DEN initiation had similar enhancing effects on the development of GST-P+ foci (P less than 0.001) . (iii) The Ames mutation test in Salmonella: both dipyrone A and dipyrone B proved weakly mutagenic for strain TA100 in the presence or absence of S9 fraction. Radiat Res, 1991 Jul, 127(1), 36 - 44 An interrelatedness of the potentiation of radiation-induced bacterial cell killing by cisplatin and binuclear rhodium carboxylates; Richmond RC et al.; Cisplatin and binuclear rhodium (Rh2) carboxylates appear to potentiate radiation-induced killing of Salmonella typhimurium cells largely as a consequence of one-electron reduction that leads to an active radiolytic product . This conclusion is supported by results from experiments wherein the hydrated electron and the hydroxyl radical are competed for in the presence of cisplatin and Rh2 carboxylates, and by the similarly shaped radiation survival curves for cisplatin and Rh2 carboxylates wherein potentiation is expressed beyond variable thresholds of radiation dose . Increasing concentrations of phosphate and chloride also inhibit radiation potentiation by both cisplatin and Rh2 carboxylates, further supporting the contention for similar mechanisms . Radiation potentiation by cisplatin is relatively much more sensitive to the inhibition by chloride. Mutat Res, 1991 Jul, 249(1), 93 - 104 Interaction with microsomal lipid as a major factor responsible for S9-mediated inhibition of 1,8-dinitropyrene mutagenicity; Shah AB et al.; 1,8-Dinitropyrene (1,8-DNP), present in polluted air, is a rodent carcinogen and a potent, direct-acting mutagen in salmonella typhimurium TA98 . This mutagenicity is markedly reduced in the presence of mammalian hepatic S9 or microsomes . We demonstrate that at least a substantial part of this effect is attributable to non-enzymatic processes . The microsomal-dependent inhibition was unaffected by omission of an NADPH-generating system or when the cytochrome P-450 inhibitor, SKF-525A, or the cytochrome P-448 inhibitor, ellipticine, was incorporated in the metabolic activation system, suggesting that mixed function oxidases are not involved . Heat inactivation partially decreased the ability of induced S9 to reduce DNP mutagenicity . Substitution of S9 with a similar concentration of bovine serum albumin did not affect DNP activity . Thus non-specific binding to microsomal protein is not involved . However, when lipids, derived from uninduced microsomes, were added to incubations of DNP and S . typhimurium TA98, mutagenicity was decreased . Furthermore, substitution of microsomal lipids with a suspension of phosphatidylcholine (PC), a major lipid constituent of microsomes, affected DNP mutagenicity similarly . An increase in PC concentration resulted in a greater inhibitory effect . The reduction in DNP mutagenicity observed with microsomal lipids or with PC was less than that detected with uninduced S9, whilst the mutagenicity of 2-nitrofluorene was reduced to an approximately equal extent by lipids and S9 . This phenomenon may be responsible for the S9-mediated detoxification of other mutagenic nitroaromatic compounds and may have important implications for mutagenicity testing. Mutat Res, 1991 Jul, 249(1), 243 - 54 Transformation of arylamines into direct-acting mutagens by reaction with nitrite; Kato T et al.; Arylamines including aniline (I), 1-naphthylamine (II), 2-naphthylamine (III), 2-aminofluorene (IV), 1-aminoanthracene (V) and 1-aminopyrene (VI) were treated with 4 equivalent amounts of nitrite at pH3 and 37 degrees C for 4 h . The reaction mixtures of I, IV, V and VI showed mutagenicity to Salmonella typhimurium TA98 and TA100 strains without metabolic activation . The numbers of His+ revertant colonies to TA98 strain were 110/0.05 mumole I, 970/0.055 mumole IV, 620/0.10 mumole V and 870/0.02 mumole VI . These arylamines were converted into mutagens with diazoquinone, diazonium and nitro functions depending on their structures . The mutagen from I was p-diazoquinone (I2) . The mutagen from IV was highly unstable fluorene-2-diazonium salt (IV1) . The mutagens from V were N3O3-introduced anthracene (V1-1) and 1-nitroanthracene (V2), and those from VI were unidentified nitro-introduced compound (VI1) and 1-nitropyrene (VI2). Mutat Res, 1991 Jul, 249(1), 119 - 23 UV-irradiation potentiates the antimutagenicity of p-aminobenzoic and p-aminosalicylic acids in Salmonella typhimurium; Gichner T et al.; UV-irradiation (254 nm, 10 or 20 J/cm2) of p-aminobenzoic acid (PABA) and p-aminosalicylic acid (NaPAS) potentiated their antimutagenicity towards N-methyl-N'-nitro-N-nitrosoguanidine mutagenesis in Salmonella typhimurium . Their inhibitory action towards the formation of the mutagen N-methyl-N-nitrosourea from the nitrosation mixture of N-methylurea and nitrite was also increased by UV-irradiation . In contrast, UV-irradiated PABA exhibited no inhibitory effects towards the mutagenicity of sodium azide or 3-azidoglycerol . Neither PABA nor NaPAS nor their UV-irradiation products were themselves mutagenic in the Ames assay. Mutat Res, 1991 Jul, 249(1), 105 - 10 Furoquinoline alkaloids as photosensitizers in Chlamydomonas reinhardtii; Schimmer O et al.; Seven naturally occurring furoquinoline alkaloids were investigated for their photobiological activity using arg-1 cells of Chlamydomonas reinhardtii . UV-A-mediated toxicity of the compounds was calculated from the colony-forming ability of the treated cells . The UV-A-mediated mutagenicity was measured by counting the number of Arg+ revertants induced by the treatment . Dictamnine was found to be the strongest mutagen as well as the most toxic compound of the group . The mutagenic activities were measured as mutation frequencies at equal substance concentration and ranked in the following order: An increase in the number of substituents on the lateral aromatic nucleus greatly decreased the photomutagenicity . Except for evolitrine, a similar ranking order was found as reported for the dark mutagenicity of these compounds in Salmonella typhimurium strain TA98 . Based on the result that furoquinolines are able to intercalate into DNA, we assume that the different mutagenic potencies may reflect differences in the geometry of the intercalation complex, which is important for the subsequent photochemical reaction. J Bacteriol, 1991 Jul, 173(13), 4144 - 54 Salmonella typhimurium prfA mutants defective in release factor 1; Elliott T et al.; Mutations have been characterized that map in the prfA gene of Salmonella typhimurium . These weak amber suppressors show increased readthrough of UAG but not UAA or UGA codons . Some hemA mutants exhibit a similar suppressor activity due to transcriptional polarity on prfA . All of the suppressors mapping in prfA are recessive to the wild type . Two mutant prfA genes were cloned onto plasmids, and their DNA sequences were determined . A method was devised for transferring the sequenced mutant alleles back to their original location in S . typhimurium via an Escherichia coli recD strain that carries the entire S . typhimurium hemA-prfA operon as a chromosomal insertion in trp . This reconstruction experiment showed that the mutations sequenced are sufficient to confer the suppressor phenotype. J Bacteriol, 1991 Jul, 173(13), 4079 - 87 Site-specific recombinase genes in three Shigella subgroups and nucleotide sequences of a pinB gene and an invertible B segment from Shigella boydii; Tominaga A et al.; Inversional switching systems in procaryotes are composed of an invertible DNA segment and a site-specific recombinase gene adjacent to or contained in the segment . Four related but functionally distinct systems have previously been characterized in detail: the Salmonella typhimurium H segment-hin gene (H-hin), phage Mu G-gin, phage P1 C-cin, and Escherichia coli e14 P-pin . In this article we report the isolation and characterization of three new recombinase genes: pinB, pinD, and defective pinF from Shigella boydii, Shigella dysenteriae, and Shigella flexneri, respectively . The genes pinB and pinD were detected by the complementation of a hin mutation of Salmonella and were able to mediate inversion of the H, P, and C segments . pinB mediated H inversion as efficiently as the hin gene did and mediated C inversion with a frequency three orders of magnitude lower than that of the cin gene . pinD mediated inversion of H and P segments with frequencies ten times as high as those for the genes intrinsic to each segment and mediated C inversion with a frequency ten times lower than that for cin . Therefore, the pinB and pinD genes were inferred to be different from each other . The invertible B segment-pinB gene cloned from S . boydii is highly homologous to the G-gin in size, organization, and nucleotide sequence of open reading frames, but the 5' constant region outside the segment is quite different in size and predicted amino acid sequence . The B segment underwent inversion in the presence of hin, pin, or cin . The defective pinF gene is suggested to hae the same origin as P-pin on e14 by the restriction map of the fragment cloned from a Pin+ transductant that was obtained in transduction from S . flexneri to E . coli delta pin. Infect Immun, 1991 Jul, 59(7), 2232 - 8 Inhibition of macrophage phagosome-lysosome fusion by Salmonella typhimurium; Buchmeier NA et al.; Salmonella typhimurium-infected macrophages were examined by electron microscopy to determine whether intracellular survival of S . typhimurium is associated with failure of bacteria containing phagosomes to fuse with secondary lysosomes . S . typhimurium 14028 actively inhibited phagosome-lysosome fusion and appeared to preferentially divide within unfused phagocytic vesicles . In comparison with Escherichia coli, S . typhimurium inhibited phagosome-lysosome fusion in peritoneal macrophages, J774 macrophages, and bone marrow-derived macrophages from both BALB/c (itys) and SWR/J (ityr) mice . The mechanism responsible for Salmonella inhibition of phagosome-lysosome fusion is unknown but requires viable salmonellae, is not blocked by opsonization with fresh normal mouse serum, and is not due to lipopolysaccharide . Inhibition of phagosome-lysosome fusion may play a critical role in survival of salmonellae within macrophages and in virulence. Avian Dis, 1991 Jul-Sep, 35(3), 435 - 42 Humoral responses and salmonellosis protection in chickens given a vitamin-dependent Salmonella typhimurium mutant; Alderton MR et al.; Humoral responses in chickens inoculated with an aromatic vitamin dependent (Aro-) Salmonella typhimurium mutant (STM) were studied to ascertain the efficacy of the organism as a vaccine for salmonellosis and possibly as a delivery system for antigens from enteric pathogens of chickens . Serum antibody responses in chickens that were given oral or subcutaneous inoculations of the bacterium followed the classic order of antibody production, with IgM being detected first, followed by IgG and IgA . Antibody responses in the gut of orally inoculated chickens were restricted to IgG and IgA . Weight gain measured in chickens given high doses of STM (up to 5 x 10(9)) orally, revealed that the bacterium did not adversely affect the chickens; in fact, inoculated chickens had significantly higher body weights than controls at the same age . Salmonellosis protection of chickens by oral vaccination with STM was examined in a vaccination/challenge experiment . The experiment revealed that oral vaccination reduced excretion of a virulent S . typhimurium used as the challenge organism. Zh Mikrobiol Epidemiol Immunobiol, 1991 Jul, (7), 11 - 4 {The adhesion of pathogenic microflora on carbon sorbents}; Grigor'ev AV et al.; The adsorbing activity of granulated carbonic sorbents SKN and KAU, as well as their oxidated forms, containing protogenic carboxylic and phenolic groups with respect to Shigella flexneri, Salmonella typhimurium, Escherichia coli, Streptococcus aureus and Pseudomonas aeruginosa pathogenic strains has been studied . As shown in this study, the process of interaction between microorganisms and carbonic sorbents has two stages . At the first stage the main role is played by long-distance electrostatic forces and at the second stage, by Van der Waals short-distance forces, as well as bonds formed between cell structures and surface groupings of carbonaceous materials . In the mechanism of interaction between microbial cells and carbons the geometry of carbon surface plays an important role . KAU(0)-1 exhibits the highest degree of adhesion with respect to pathogenic bacteria. Mutagenesis, 1991 Jul, 6(4), 289 - 95 Study on the mutagenic activity of 13 bioflavonoids with the Salmonella Ara test; Jurado J et al.; The mutagenicity of 13 flavonoids has been investigated with the L-arabinose forward mutation assay of Salmonella typhimurium . Each flavonoid was tested by both plate incorporation and preincubation mutagenesis protocols in the presence or the absence of mammalian metabolic activation (S9 mixture) . All flavonoids gave a dose-response relationship and induced a number of AraR mutants considered statistically significant . Their minimum mutagenic doses (MMD) differed markedly in the Ara test, covering a 400-fold range: from 4 nmol for quercetin to 1626 nmol for taxifolin . Flavonols were the strongest mutagens, with mutagenic potencies (MMD-1) representing from 27 to approximately 2% that of quercetin . Comparatively, the mutagenicities of other flavonoids represented only less than or equal to 1% . The data reported in this paper for the Ara forward mutation test suggest structural requirements for mutagenicity of bioflavonoids like those previously reported for the His reverse mutation assay: (i) flavonols with a free hydroxyl at position 3 are the strongest mutagenic flavonoids, (ii) saturation of the 2,3 double bond diminishes the mutagenic potency, and (iii) free hydroxyl groups at positions 3' and 4' influence the non-requirement for metabolic activation . The mutagenic properties of quercetin and rutin in the Ara test support the idea that these flavonols are not the major putative mutagens in complex mixtures such as wine. Mutagenesis, 1991 Jul, 6(4), 261 - 9 Genotoxicity of p-nitrocinnamaldehyde and related alpha, beta-unsaturated carbonyl compounds in two bacterial assays; Eder E et al.; Seventeen cinnamaldehydes, cinnamic acids, 2-furylacroleins and related compounds were tested in the Salmonella preincubation reversion assay and in the SOS chromotest . Of eight compounds containing nitrogroups, seven were clearly mutagenic in the presence of S9 mix and six in its absence; whereas none of the parent compounds not containing a nitrogroup and none of the congeners containing chlorine, methoxy or amino groups were mutagenic . Metabolic epoxidation was excluded in additional experiments using SKF525, an inhibitor of mono-oxygenases, and trichloropropene oxide, an inhibitor of epoxide hydrolases . Less or no mutagenicity was found in the nitroreductase deficient strains Salmonella typhimurium TA100NR or TA98NR and in the O-acetyltransferase deficient strains TA100/1,8-DNP6 or TA98/1,8-DNP6 except with 5-nitro-2-furylacrolein which exhibited decreased mutagenicity in TA100NR when compared with TA100 but the highest mutagenicity in TA100/1,8-DNP6 . Less or no genotoxic activity was found in the SOS chromotest when using the nitroreductase deficient Escherichia coli strain PQ253 whereas all seven compounds tested were positive in strain PQ37 . The results demonstrate the importance of the nitro group and that the compounds are activated either by bacterial nitroreductase or by the nitroreductase in the S9 mix . A chemical activation of the acrolein moiety by the negative inductive effect of the nitro group is unlikely . The genotoxicity of the cinnamyl compounds is dependent on the position of the nitro group in the phenyl ring . The genotoxicities of the p-nitro compounds were about two orders of magnitude higher than those of the ortho and meta congeners . The comparison between the Ames test and the SOS chromotest showed good agreement. Mol Microbiol, 1991 Jul, 5(7), 1741 - 3 Absence of acetohydroxy acid synthase III in Salmonella typhimurium is due to early termination of translation within the ilvl gene; Ricca E et al.; The cryptic ilvlH locus of Salmonella typhimurium has genetic information for two distinct subunits of acetohydroxy acid synthase III . We show that the ilvH-encoded subunit is normally translated and the lack of activity is due to early termination of translation within the promoter-proximal ilvl gene . Analysis of the 5' region of the operon led to identification of the promoter and the amino-terminal part of ilvl . Expression of this gene in a mutant producing acetohydroxy acid synthase is due to a transversion which creates a UUA (leucine) codon in the place of a UGA (stop) codon present in position 12 of the wild-type coding region. Cell Biol Toxicol, 1991 Jul, 7(3), 281 - 306 1986 survey of genetic toxicology testing in industry, government contract, and academic laboratories; Auletta AE et al.; Results of the 1986 Genetic Toxicology Association's survey of industrial, government, contract, and academic laboratories on the status of several assays in genetic toxicology are presented below . 1 . The most commonly used assay was the Salmonella typhimurium/mammalian microsomal (Ames) assay, which was used by 83% of all respondents . 2 . The next five (5) most commonly used assays were in vitro cytogenetics (72%), in vivo cytogenetics (59%), CHO HGPRT gene mutation (55%), the micronucleus assay (53%), and L517BY gene mutation (45%) . 3 . The assay showing the greatest percentage increase in routine use was the micronucleus assay which went from 14% in 1984 to 34% in 1986, an increase of 20% . 4 . Other assays which increased in routine use were CHO HGPRT mutation (+18%); in vitro cytogenetics (+14%); L5178Y gene mutation (+9%), and the Ames assay (+5%) . 5 . Routine use of in vitro UDS assays declined by 6%; use of in vitro SCE assays declined by 12% . 6 . There was no change in the rate of routine use of in vivo cytogenetics or in vivo SCE assays . 7 . Assays routinely performed on contract included the Salmonella assay, CHO HGPRT gene mutation, in vitro cytogenetics, in vitro UDS, in vivo cytogenetics, the micronucleus assay, L5178Y gene mutation, and the Drosophila sex-linked recessive lethal assay . 8 . Four assays were being developed by five or more laboratories . These included in vitro SCE (8); the micronucleus assay (7); in vivo SCE (6); and DNA adduct formation (5) . 9 . A total of 17 assays had been abandoned by one or more laboratories . However, since no assay had been given up by more than three laboratories no conclusions can be drawn about the overall robustness of any of the assays on the survey form. J Pediatr Gastroenterol Nutr, 1991 Jul, 13(1), 101 - 3 Salmonella typhimurium appendicitis; Kazlow PG et al.; A child with signs and symptoms of acute gastroenteritis developed localization of her pain to the right lower quadrant . A clinical diagnosis of appendicitis was made and an inflamed appendix was found at surgery . The postoperative period was marked by high spiking fevers and profuse nonbloody diarrhea . Cultures of the appendix and the stool revealed Salmonella typhimurium . Nontyphoidal Salmonella organisms are a rare cause of acute suppurative appendicitis . Intraoperative cultures of the appendix and peritoneal fluid as well as postoperative cultures of the diarrheal fluid were crucial in elucidating the cause of this patient's unusual course. FEMS Microbiol Lett, 1991 Jul 1, 65(3), 345 - 51 Lack of specific hybridization between the lep genes of Salmonella typhimurium and Bacillus licheniformis; van Dijl JM et al.; This paper describes an attempt to clone the Bacillus licheniformis lep gene, encoding signal peptidase, using the Salmonella typhimurium lep gene as a hybridization probe . Although a hybridizing fragment was obtained, DNA sequence analysis indicated that it did not contain the lep gene . Instead, the protein encoded by the cloned fragment showed similarity with a variety of L-asparaginases. FEMS Microbiol Lett, 1991 Jul 1, 65(3), 305 - 9 Construction and evaluation of a cea-lacZ gene fusion for the detection of environmental mutagens and carcinogens; Schumann W et al.; The cea-kil operon of the ColE1 plasmid is negatively regulated by the LexA-repressor and therefore, it is under the control of SOS regulation . We constructed a gene fusion between the cea and lacZ genes . Expression of the translational fusion can be easily detected by monitoring the levels of beta-galactosidase . Since the whole detection system is plasmid-based, it can be used in both Escherichia coli and Salmonella typhimurium strains . The SOS-function-inducing activities of 14 chemical mutagens were investigated in E . coli K12 and in two S . typhimurium Ames-strains and compared with results obtained by the SOS-chromotest and by the Umu-test . To correct for the inhibitory effects of test chemicals on mRNA and/or protein synthesis, the level of the constitutive chloramphenicol acetyl transferase was assayed in parallel. Chem Res Toxicol, 1991 Jul-Aug, 4(4), 445 - 53 Isolation and characterization of N7-guanyl adducts derived from 1,2-dibromo-3-chloropropane; Humphreys WG et al.; 1,2-Dibromo-3-chloropropane is a potent renal and testicular toxicant and has been shown to induce tumor formation in laboratory animals . The toxic effects of the compound are thought to be a result of a bioactivation step in which a glutathione conjugate is formed and subsequently reacts with cellular DNA . The L-glutathione conjugate of 1,2-dibromo-3-chloropropane was chemically synthesized and used to alkylate DNA: following incubations of the conjugate with calf thymus DNA and neutral thermal hydrolysis (to release N7-guanyl adducts) four major fluorescent products were observed . Three of these were isolated and characterized, the structures being determined as S-{bis(N7-guanylmethyl)methyl}glutathione and the two diastereomers of S-{1-(hydroxymethyl)-2-(N7-guanyl)ethyl}glutathione . The fourth fluorescent product was unstable and formed in low yield and thus could not be characterized . The formation of these N7-guanyl adducts can be explained by a mechanism that includes the formation of two consecutive episulfonium ion intermediates followed by nucleophilic attack at the unsubstituted methylene carbon . These adducts bear structural and mechanistic similarities to the major adduct derived from 1,2-dibromoethane, S-{2-(N7-guanyl)ethyl}glutathione . The same adducts were also formed when DBCP was incubated with rat liver cytosol, GSH, and DNA . In vivo experiments with DBCP yielded very low levels of the N7-guanyl adducts formed in rat liver compared to the levels seen after treatments with 1,2-dibromoethane . The bis-guanyl adduct represents a cross-linked structure that may be important in the toxicity of this compound . The conjugate was not found to be mutagenic to Salmonella typhimurium TA100 but rather showed a toxic effect toward the bacteria. J Vet Diagn Invest, 1991 Jul, 3(3), 218 - 22 Use of a Salmonella typhimurium-derived virulence probe in the detection of Salmonella sp . and in the characterization of S . cholerae-suis virulence plasmids; Maddox CW et al.; A genetic probe encoding a virulence gene from Salmonella typhimurium was useful in the detection of Salmonella from feces during an outbreak of salmonellosis at a local dairy . A 3.2-kb BamHI restriction endonuclease fragment of the S . typhimurium virulence plasmid, pStSR100, has been useful as a DNA probe for both detection of Salmonella sp . and characterization of virulence plasmids from numerous field isolates . This virA probe hybridizes to a highly conserved gene carried on the large virulence plasmids of invasive Salmonella isolates . Colony blots prepared from feces directly plated onto MaConkey's agar failed to detect low numbers of Salmonella sp . However, hybridization of the VirA probe to vacuum blots or colony blots prepared from feces in tetrathionate enrichment broth incubated for 16 hours at 37 C was effective for detecting Salmonella sp . and resulted in an 85.9% correlation with culture results . The probe also demonstrated the highly conserved nature (96%) of the virulence gene among S . cholerae-suis isolate plasmids detected using Southern blot analysis. J Mol Evol, 1991 Jul, 33(1), 23 - 33 Determinants of DNA sequence divergence between Escherichia coli and Salmonella typhimurium: codon usage, map position, and concerted evolution; Sharp PM; The nature and extent of DNA sequence divergence between homologous protein-coding genes from Escherichia coli and Salmonella typhimurium have been examined . The degree of divergence varies greatly among genes at both synonymous (silent) and nonsynonymous sites . Much of the variation in silent substitution rates can be explained by natural selection on synonymous codon usage, varying in intensity with gene expression level . Silent substitution rates also vary significantly with chromosomal location, with genes near oriC having lower divergence . Certain genes have been examined in more detail . In particular, the duplicate genes encoding elongation factor Tu, tufA and tufB, from S . typhimurium have been compared to their E . coli homologues . As expected these very highly expressed genes have high codon usage bias and have diverged very little between the two species . Interestingly, these genes, which are widely spaced on the bacterial chromosome, also appear to be undergoing concerted evolution, i.e., there has been exchange between the loci subsequent to the divergence of the two species. Carcinogenesis, 1991 Jul, 12(7), 1359 - 62 Mutagenicity of benzo{a}pyrene bay-region sulfonates; Green JL et al.; The interaction between the sulfite anion and specific benzo{a}pyrene (B{a}P) derivatives produces a novel class of benzo{a}pyrene sulfonates . (+/-)-7,8,9-Trihydroxy-7,8,9,10-tetrahydrobenzo{a}pyrene-10-sulfonate (B{a}PT-10-sulfonate) is formed in high yields in incubations containing (+/-)-7r,8t-dihydroxy-9t,10t-epoxy-7,8,9,10-tetrahydrobenzo{a}pyre ne (anti-BPDE) and sulfite, and sulfite strongly enhances the mutagenicity of the diolepoxide toward Salmonella typhimurium under those conditions . Although B{a}PT-10-sulfonate itself shows little direct mutagenicity over a 1-20 microM concentration range, this reactive bay-region intermediate does enhance the mutagenicity of anti-BPDE in strains TA98 and TA100 by up to 280% . No significant enhancement was seen when up to 20 microM B{a}PT-10-sulfonate was used in concert with another direct-acting mutagen, N-acetoxy-acetylaminofluorene (N-AcO-AAF) . The isomeric product derived from sulfite and (+/-)-7,8-dihydroxy-7,8-dihydrobenzo{a}pyrene (B{a}P-7,8-diol) is (+/-)-7,8,10-trihydroxy-7,8,9,10-tetrahydrobenzo{a}pyrene-9-sulfonate (B{a}PT-9-sulfonate) . Like B{a}PT-10-sulfonate, B{a}PT-9-sulfonate is not mutagenic to strains TA97, TA98 and TA100 . This sulfonate exhibited little enhancing activity with anti-BPDE over a 1-20 microM concentration range, but did enhance the mutagenic response of strain TA98 to 0.2 microM N-Aco-AAF by up to 128% . Sulfite, anti-BPDE and B{a}PT-sulfonates were also examined for the ability to induce a forward mutation at the hgprt locus (8-azaguanine resistance) in strains of S.typhimurium . Sulfite caused a marked enhancement of forward mutation due to anti-BPDE in both TA98 and TA100 . Surprisingly, concurrent administration of B{a}PT-10-sulfonate with anti-BPDE did not increase the number of mutant colonies . The extensive conversion of anti-BPDE to B{a}PT-10-sulfonate under conditions where sulfite enhances diolepoxide mutagenicity, when coupled with this enhancement of diolepoxide mutagenicity by B{a}PT-10-sulfonate in the reverse mutation assay, supports this novel B{a}P derivative as a mediator of the sulfite-dependent enhancement of B{a}P genotoxicity . Determining why this enhancing effect was not seen when selecting for mutation at the hgprt locus of S.typhimurium will require further study. Mutat Res, 1991 Jul, 260(3), 271 - 9 Bacterial mutagenicity of two cyclopentafused isomers of benzpyrene; Ball LM et al.; Two novel cyclopentafused polycyclic aromatic hydrocarbons, naphtho(1,2,3-mno)acephenanthrylene (cyclopenta benzo{e}pyrene) and naphtho(2,1,8-hij)acephenanthrylene (cyclopenta(ij)benzo{a}pyrene) were evaluated for mutagenic activity in the Ames Salmonella typhimurium plate incorporation assay . Both compounds required S9 metabolic activation, and showed optimal activity at low S9 concentrations (below 0.6 mg/plate) . Both compounds induced frameshift and base-pair substitution mutations, being active in strains TA98, TA100, TA1537, TA1538 and TA104, but not in strain TA1535 . Cyclopenta(ij)benzo{a}pyrene was more active than cyclopentabenzo{e}pyrene, and both were more potent than their parent ring systems, benzo{a}pyrene and benzo{e}pyrene, respectively . Cyclopenta(ij)benzo{a}pyrene was more active in strain TA104 than in TA100 or TA98 (250-470, 340 and 80-100 rev/nmole) as was benzo{a}pyrene (120, 70 and 40 rev/nmole respectively); cyclopentabenzo{e}pyrene was more active in TA100 than TA104 or TA98 (70 versus 50 and 40 rev/nmole), and benzo{e}pyrene showed a similar pattern (4, 3.5 and 0.6 rev/nmole) . The relative potencies of the four compounds are in accord with predictions based on perturbational molecular orbital calculations . The peak of activity at low S9 concentrations is consistent with epoxidation at the cyclopentafused ring being the major route of metabolic activation for both these cyclopentafused compounds. J Toxicol Environ Health, 1991 Jul, 33(3), 317 - 26 Short-term dermal toxicity and mutagenicity of coal coprocessing products in the rat; Chu I et al.; The present study was conducted to determine the dermal toxicity of coal coprocessing products and to assess their potential health hazards . Groups of 10 male and 10 female Sprague-Dawley rats were administered dermally coal coprocessing products (light gas oil, LGO; heavy gas oil I, HGOI; heavy gas oil II, HGOII) at 1 g/kg body weight/d for 14 d . The control and positive control groups received normal saline and a coal liquefaction product (CLP) at the same dose level, respectively . Treatment with either the three fractions of coprocessing products or CLP caused decreased growth rate and food consumption in animals of both sexes . Liver enlargement occurred in groups treated with HGOI, HGOII, and CLP . Decreased serum glucose was observed in animals of both sexes treated with the three fractions and CLP . Treatment with HGOI and CLP caused an elevation of hepatic microsomal ethoxyresorufin deethylase activity in the rat of both sexes . The three fractions and CLP caused mild anemia . Mild treatment-related histological changes were observed in the liver, spleen, thyroid, bone marrow, and kidney . All three fractions of coprocessing products were tested for their mutagenicity in five strains of Salmonella typhimurium: TA98, TA100, TA1535, TA1537, and TA1538 . HGOI, after metabolic activation, was found to be mutagenic in the strains of TA98, TA100, and TA1538 . In contrast, HGOII was mutagenic in the five strains with or without metabolic activation . These data indicate that HGOI and HGOII are more toxic than LGO, and should be subjected to further studies to determine their long-term effects. Gut, 1991 Jul, 32(7), 787 - 90 Prospective hospital based study on persistent diarrhoea; Dutta P et al.; A total of 383 children aged less than 5 years suffering from acute watery diarrhoea or dysentery were studied in hospital to determine the rate of persistent diarrhoea . Altogether 335 (87.5%) recovered within 13 days . Only in 48 (12.5%) did the diarrhoea continue for 14 days or more, and they were considered as having persistent diarrhoea . Children aged between 7 and 18 months had a significantly increased incidence of persistent diarrhoea . Children suffering from grade II-IV malnutrition constituted the majority (70.8%) of those with persistent diarrhoea . Higher rates of isolation of Shigella flexneri, Shigella dysenteriae 1, and Salmonella typhimurium were observed among patients with persistent diarrhoea than in those with diarrhoea of shorter duration . No positive correlations were observed between the clinical severity of disease at hospital admission and measles . Breast fed babies were not prone to persistent diarrhoea. Am J Pathol, 1991 Jul, 139(1), 177 - 84 Salmonella-induced M-cell formation in germ-free mouse Peyer's patch tissue; Savidge TC et al.; M cells present in Peyer's patch tissue transport enteric antigens for presentation to underlying lymphoid tissue to initiate immune responses against intestinal infection . Present work investigates how interactions taking place between bacteria, epithelial cells, and immunocytes could contribute to initial detection and later elimination of enteric antigens . Oral infection of germ-free mice with Salmonella typhimurium aroA- caused a twofold to threefold increase in M cell numbers, crypt depth, and enterocyte migration rate after 7 days . These changes were accompanied by a twofold increase in follicle-associated epithelial tissue (FAE)-associated CD4+ and a threefold decrease in FAE-associated CD8+ counts . Salmonella also increased M-cell numbers shortly after infection . Other effects on crypt size and spleen weight took longer to develop . Salmonella probably creates M cells by changing the local subepithelial immune environment in the lymphoid follicle. Toxicol Appl Pharmacol, 1991 Jul, 109(3), 538 - 46 Mutagenesis and DNA adduct formation by 1-nitropyrene in Chinese hamster ovary cells without exogenous metabolic activation; Thornton-Manning JR et al.; The direct-acting mutagenicity of 1-nitropyrene (1-NP), a tumorigenic environmental pollutant and model nitropolycyclic aromatic hydrocarbon, was studied in Chinese hamster ovary (CHO) cells . Previous reports indicated that 1-NP, a potent direct-acting mutagen in Salmonella typhimurium, was mutagenic in CHO cells only in the presence of an exogenous activation system . In this study, a DNA-repair-deficient CHO cell line, CHO-UV5, and the repair-proficient CHO-K1-BH4 cell line were used to measure the direct-acting mutagenicity of highly purified samples of 1-NP . Exposure of CHO-K1-BH4 cells for 5, 12, and 24 hr did not increase mutations at the hypoxanthine-guanine phosphoribosyl transferase (hprt) locus (p greater than 0.1; paired t test; n = 5-6), while treatment of CHO-UV5 cells for 24 hr produced a statistically significant induction of mutants (22 +/- 6 mutants per 10(6) clonable cells vs a solvent control value of 9 +/- 3 per 10(6) cells; p less than 0.01; n = 6) . 32P-Postlabeling analysis of the DNA adducts formed in CHO-UV5 cells following 1-NP exposure revealed the presence of a single major adduct . Based on its chromatographic properties, its sensitivity to nuclease P1 digestion, and its resistance to hydrazine treatment, the adduct appeared to be N-(deoxyguanosin-8-yl)-1-aminopyrene, which was presumably produced by nitroreduction of 1-NP to N-hydroxy-1-aminopyrene . These results suggest that the use of extended treatment times and DNA-repair-deficient cells may be required to assess adequately the mutagenicity of nitropolycyclic aromatic hydrocarbons in CHO cells. Toxicol Appl Pharmacol, 1991 Jul, 109(3), 494 - 506 Immunotoxicity of 2-methoxyethanol following oral administration in Fischer 344 rats; Smialowicz RJ et al.; The immunotoxicity of the glycol ether 2-methoxyethanol (ME) was evaluated in adult Fischer 344 rats using a variety of in vitro and in vivo immune function assays . In the first phase of this study, male rats were dosed by oral gavage with ME in water, at dosages ranging from 50 to 200 mg/kg/day, for 10 consecutive days . Decreases in thymus weights were observed at dosages of 50-200 mg/kg/day in the absence of decreased body weights . Lymphoproliferative (LP) responses to concanavalin A and phytohemagglutinin were reduced at 50-200 mg/kg/day while pokeweed mitogen and Salmonella typhimurium mitogen responses were reduced at 200 mg/kg/day . No alterations were observed in natural killer cell activity, mixed lymphocyte reaction, or cytotoxic T lymphocyte responses . The frequency of W3/25-positive splenocytes was reduced in rats dosed at 200 mg/kg/day . Interleukin-2 production was reduced in splenocytes from rats exposed to all dosages of ME . The plaque-forming cell (PFC) response to sheep red blood cells was enhanced in rats dosed at 50 mg/kg/day . However, the PFC response to trinitrophenyl-lipopolysaccharide (TNP-LPS) was suppressed at all dosages . Similarly, the PFC response to TNP-LPS was suppressed in adult female rats dosed with ME . A reduction in the expulsion of adult worms was observed in rats dosed at 200 mg/kg/day that were infected with Trichinella spiralis . A number of male reproductive parameters were also evaluated in rats dosed with ME over 10 days . A significant reduction in testicular weight was observed in rats dosed at 200 mg/kg/day . In the second phase of this study, the PFC response to TNP-LPS was employed to assess the role that metabolism of ME to 2-methoxyacetic acid (MAA) plays in the immunotoxicity of this glycol ether . Ten-day oral dosing with MAA resulted in the inhibition of the PFC response to TNP-LPS at dosages of 50-200 mg/kg/day . Concomitant exposure of rats to ME and the alcohol dehydrogenase inhibitor 4-methylpyrazole blocked ME-induced suppression of this PFC response . Attempts to ameliorate ME-induced suppression of the PFC response with serine, which has been shown to reverse ME-induced developmental and reproductive toxicity, were unsuccessful . These results suggest that the immune system may be more sensitive than the reproductive system to the toxic effects of ME . Furthermore, it appears that MAA is the proximate toxicant for ME-induced alterations in the immune system, as has been demonstrated for ME-induced reproductive and developmental toxicity. Rev Chil Pediatr, 1991 Jul-Aug, 62(4), 221 - 6 {Adenosine deaminase in typhoid fever and other febrile diseases}; Casanueva V et al.; The contribution of serum adenosine deaminase (ADA) activity to the diagnosis of typhoid fever was assessed in 246 children and in 46 adults, by Giusti's original technique . Children included otherwise healthy patients admitted for elective surgical conditions or under follow up for epilepsy which were considered to be a control group (n: 81), presumptive viral diseases (n: 31), miscellaneous febrile diseases except for typhoid fever (n: 41), different kinds of bacteremia (n: 6), diarrhea due to Salmonella typhimurium (n: 14), viral hepatitis (n: 24), and culture proven typhoid fever (n: 49) . Adult's group included 39 healthy controls and 7 patients with culture proven typhoid fever . Among children mean ADA activity was as follows: control group 28 +/- 7.8, viral disease 35.3 +/- 13.1, miscellaneous febrile disease 36.1 +/- 15.6, bacteremia group: 30.3 +/- 10.3, salmonellosis group 51.6 +/- 9, hepatitis group 68.3 +/- 34.5, typhoid fever group 124.4 +/- 40.8 U/I 37 degrees C . Among adults, values were 18.4 +/- 7.5 for controls and 112.8 +/- 19.2 U/I 37 degrees C in typhoid fever patients . In both adults and children ADA activity was significantly higher in the typhoid fever group (p < 0.0001) . Untreated typhoid fever patients had their higher ADA activity between 10th and 15th day of illness . When ADA cut point was set at 80 U/I, sensitivity of the test was 91.8% and specificity was 91.4% as a preliminary clue to the recognition of typhoid fever. J Immunol, 1991 Jul 1, 147(1), 224 - 30 Modulation of mouse complement receptors 1 and 2 suppresses antibody responses in vivo; Thyphronitis G et al.; A mAb, 7G6, that binds to mouse CR1 and CR2 and down-modulates their expression on splenic B cells in vivo, was used to determine whether a decrease in CR1 and CR2 expression affects antibody responses to different T-dependent and T-independent Ag . Injection of mice with the mAb 7G6 prior to immunization with FITC haptenated Salmonella typhimurium (SH5771), Salmonella montevideo (SH5770), SRBC, or Ficoll dramatically decreased subsequent antibody responses to FITC . Although both IgM and IgG primary antibody responses were affected similarly, the antibody levels were most inhibited during early phases of the response . In contrast, down-modulation of the CR did not affect memory antibody responses, because injection of mice with 7G6 before a second immunization with FITC-SH5771 had no effect on subsequent anti-FITC antibody production . Moreover, polyclonal in vivo activation of the mouse immune system by anti-mouse IgD antibodies was not affected by previous administration of 7G6, because anti-IgD-induced increases in Ia expression and serum IgG1 levels were not affected . Taken together, these observations suggest that CR1 and CR2 may play an important role in enhancing primary antibody responses to many T-dependent and T-independent Ag and may contribute to a host's response to naturally occurring antigens such as bacteria. J Mol Recognit, 1991 Jul-Dec, 4(4), 121 - 8 Studies of the binding activity of phage G13 to synthetic trisaccharides analogous to binding structures in Salmonella typhimurium and Escherichia coli C core saccharide . Correlation between conformation and binding activity; Bruse GW et al.; Phage G13 binds to the carbohydrate part of lipopolysaccharides from rough mutants of Salmonella and Escherichia coli as the first event of infection . Equilibrium dialysis inhibition studies with native and synthetic trisaccharides as inhibitors suggested that phage G13 recognizes branched oligosaccharides having 6-O-alpha- or 7-O-alpha-glycosyl groups with alpha-Man(1----3) {alpha-Man(1----6)}Man (Man{Man}Man) and alpha-Glc(1----3)-{alpha-Hep(1----7)} alpha-Hep(1----3) alpha-Hep(1----5)Kdo as the smallest saccharides with inhibitory activity (Wollin et al., 1989) . Of four synthetic analogues to Man{Man}Man only Man(1----3){alpha-Gal(1----6)}alpha-Man-OMe (Man{Gal}-Man) and alpha-Glc(1----3){alpha-Hep(1----7)}alpha-Hep-OMe (Glc{Hep}Hep) inhibited the binding of labelled E . coli C core nonasaccharide ligand to G13 with activities which were 10- and 15-fold lower than Man{Man}Man . The trisaccharides alpha-Man(1----3){alpha-Glc(1----6){alpha-Man-OMe (Man{Glc}Mann) and alpha-Man(1---3){alpha-Tal(1----6)}alpha-Man-OMe (Man{Tal}Man) showed no inhibition at concentrations 75-fold higher than Man{Man}Man . Minimum energy conformation calculations of the saccharides using the GESA method showed that the 6-O-alpha-Man group in Man{Man}Man and the 7-O-alpha-Hep group SL805 pentasaccharide expose their OH-2 and OH-3 groups in a similar way and these are postulated to be key structural features for binding activity . The importance of hydroxy groups at certain positions is implied from the fact that both manno- and galacto-isomers are active . We also conclude that the O6-C6-C5-O5-C1 region of the 3-O-alpha-glycosyl group in the Man{Man}Man trisaccharide, or part of it, is important for the G13 binding activity. Microb Pathog, 1991 Jul, 11(1), 33 - 8 Serum TNF alpha in mouse typhoid and enhancement of a Salmonella infection by anti-TNF alpha antibodies; Mastroeni P et al.; Tumour necrosis factor alpha (TNF alpha) was detected by the L929 cell assay in the sera of mice 1 h after large i.v . inocula of virulent Salmonella typhimurium C5 . TNF alpha was not detectable in sera from innately susceptible BALB/c mice during the course of a lethal infection commencing from a low inoculum, or from resistant A/J mice during the course of a lethal or sublethal infection, but only 1 h after i.v . challenge with large numbers of organisms . Administration of a single dose of rabbit polyclonal anti-TNF alpha antiserum on day 1 had no effect on the early course of a lethal infection in A/J mice . However, the same treatment exacerbated a sublethal infection in A/J mice . Anti-TNF alpha treatment did not accelerate the early bacterial net growth rate in the RES . Instead, the cfu count in treated mice continued to increase past the point at which the host response suppressed a further increase in bacterial numbers (the plateau phase) in normal controls . A second dose of anti-TNF alpha antiserum on day 4 together with a higher but still sublethal challenge caused a lethal infection in A/J mice . The results indicate that TNF alpha is important in mediating the plateau phase in a salmonella infection, and its effect may be local. Indian J Exp Biol, 1991 Jul, 29(7), 676 - 8 Mutagenicity of nitrosated food items; Balachandran B et al.; Several food items, commonly consumed in South India, after nitrite treatment under simulated gastric conditions were found to be mutagenic in Salmonella typhimurium tester strain TA 100 . Dichloromethane extracts containing the volatile nitroso compounds and ethyl-acetate extracts with the non-volatile nitroso compounds of some of the food items exhibited mutagenicity. J Neurosurg Sci, 1991 Jul-Sep, 35(3), 165 - 8 Brain abscess caused by Salmonella typhimurium . Case report and review of the literature; Iplikcioglu AC et al.; Brain abscess due to Salmonella species are very rare . In this paper a case of brain abscess caused by Salmonella typhimurium is reported . The patient had no history of Salmonellosis . A review of the literature is also presented. New Biol, 1991 Jul, 3(7), 687 - 97 A cluster of genes that affects nucleoid segregation in Salmonella typhimurium; Luttinger AL et al.; Thirteen conditional lethal mutations in genes of Salmonella typhimurium map at the clmF locus and affect both viability and the faithful partitioning of daughter nucleoids . These mutations have now been divided into three complementation groups by using cloned fragments of S . typhimurium DNA and renamed parC, parE, and parF . The proteins produced from the cloned fragments predict that ParC is an 85-kD protein, ParE is 75 kD in size, and ParF, 27 kD . The parE gene is about 5 kb upstream of the parC gene, and parC is just upstream of parF . Genes situated between parC and parE produce at least two proteins of unknown function . The DNA sequence of the S . typhimurium parC gene was determined and has 56% homology with the first 1400 base pairs of the Escherichia coli gryA gene, which encodes the A subunit of DNA gyrase, and 85% homology with the E . coli parC gene . Despite the strong homology between gryA and parC, these two genes cannot substitute for one another . The DNA sequence of the S . typhimurium parF gene was determined and predicts a protein with a hydrophobic N terminus . The ParF protein may interact with ParC and ParE to anchor these proteins to the membrane . These results raise questions about the relative roles of gyrase and ParCEF in nucleoid decatenation . In addition, the parC and gyrA genes provide an example of the evolution of essential functions by gene duplication. J Gen Microbiol, 1991 Jul, 137 ( Pt 7), 1557 - 64 Chlamydia trachomatis major outer membrane protein epitopes expressed as fusions with LamB in an attenuated aro A strain of Salmonella typhimurium; their application as potential immunogens; Hayes LJ et al.; The major outer-membrane protein (MOMP) of Chlamydia trachomatis is the focus of attention for chlamydial vaccine design, particularly those serovar- and subspecies-specific epitopes which provoke neutralizing immune responses . Selected surface-exposed B-cell epitopes of MOMP, incorporating B-subspecies specificities, were expressed as fusions with LamB, an inducible outer-membrane transport protein of Escherichia coli . These recombinant chlamydial-LamB proteins were correctly transported to the outer membrane of both E . coli and an aro A mutant of Salmonella typhimurium . The immunogenicity of the constructs was investigated in a mouse model of chlamydial salpingitis . After oral immunization, recombinant S . typhimurium were recovered from the livers of mice for up to two weeks, and a serum IgG response was induced both to the Salmonella and to the inserted chlamydial epitopes . By contrast, intravenous inoculation was ineffective . Although these LamB fusions proved only weakly immunogenic, this approach should be useful for investigating the ability of attenuated S . typhimurium vaccines incorporating chlamydial epitopes to stimulate protective mucosal immunity in the mouse model of chlamydial salpingitis. Mol Gen Genet, 1991 Jul, 227(3), 438 - 45 Selective cloning of genes encoding RNase H from Salmonella typhimurium, Saccharomyces cerevisiae and Escherichia coli rnh mutant; Itaya M et al.; We have cloned genes encoding RNase H from Escherichia coli rnh mutants, Salmonella typhimurium and Saccharomyces cerevisiae . Selection was accomplished by suppression of the temperature-sensitive growth phenotype of Escherichia coli strains containing the rnh-339::cat and either recB270 (Ts) or recC271 (Ts) mutations . RNases H from E . coli and S . typhimurium contained 155 amino acid residues and differed at only 11 positions . The S . cerevisiae and E . coli RNases H were about 30% homologous . A comparison of the amino acid sequences of several RNases H from cellular and retroviral sources revealed some strongly conserved regions as well as variable regions; the carboxyl-terminus was particularly variable . The overlapping, divergent promoter gene organization found in E . coli was observed to be present in S . typhimurium. Mutat Res, 1991 Jul, 263(3), 179 - 84 Precise excision of Tn10 in Salmonella typhimurium: effects of mutations in the polA, dam, mutH and mutB genes and of methionine or ethionine in the plating medium; Hafner LM et al.; Precise excision of Tn10 occurs at significantly elevated frequencies in cultures of the polA7 mutant strain of Salmonella typhimurium, is further increased in polA7 dam-1 and polA7 mutB strains and decreased in a polA7 mutH background . The numbers of precise excision events occurring in polA7 strains are also significantly increased when methionine (20 micrograms/ml or less) is present in the medium but decreased when ethionine (again, 20 micrograms/ml or less) is present . When both amino present, the outcome is about a 2-fold increase in precise excision events . The involvement of mismatch repair and methylation patterns in precise excision events is discussed. Mutat Res, 1991 Jul, 255(1), 95 - 100 RecA-dependent increased precise excision of Tn10 in Salmonella typhimurium; Levy MS et al.; UV irradiation induced the precise excision of Tn10 inserted in met, trp or srl in a Salmonella typhimurium strain; mitomycin C was also found to induce the frequency of precise excision of Tn10 from srl or met . Precise excision of Tn10 was not increased by either UV or mitomycin C in a recA mutant . Similarly, a recA mutant derived from a uvrD strain showed a drastic reduction in the high spontaneous levels of precise excision of Tn10 of this strain . These results indicate that recA is involved in the increased precise excision of Tn10 . In contrast to point mutations excision of Tn10 was found to be UV inducible in a top mutant. Science, 1991 Jun 28, 252(5014), 1845 - 8 Subunit communication in the anthranilate synthase complex from Salmonella typhimurium; Caligiuri MG et al.; The anthranilate synthase-phosphoribosyl transferase complex of the tryptophan biosynthetic pathway in Salmonella typhimurium is an allosteric, heterotetrameric (TrpE2-TrpD2) enzyme whose multiple activities are negatively feedback-regulated by L-tryptophan . A hybrid complex containing one catalytically active, feedback-insensitive and one catalytically inactive, feedback-sensitive mutant TrpE subunit was assembled in vitro and used to investigate communication between regulatory and catalytic sites located on different subunits . The properties of the hybrid complex demonstrate that the binding of a single inhibitor molecule to one TrpE subunit is sufficient for the propagation of a conformational change that affects the active site of the companion subunit. Biochemistry, 1991 Jun 18, 30(24), 5858 - 66 Interactions between magainin 2 and Salmonella typhimurium outer membranes: effect of lipopolysaccharide structure; Rana FR et al.; The role of the outer membrane and lipopolysaccharide (LPS) in the interaction between the small cationic antimicrobial peptide magainin 2 and the Gram-negative cell envelope was studied by FT-IR spectroscopy . Magainin 2 alters the thermotropic properties of the outer membrane-peptidoglycan complexes from wild-type Salmonella typhimurium and a series of LPS mutants which display differential susceptibility to the bactericidal activity of cationic antibiotics . These results are correlated with the LPS phosphorylation pattern and charge (characterized by high-resolution 31P NMR) and outer membrane lipid composition, and are compared to the bactericidal susceptibility . LPS mutants show a progressive loss of resistance to killing by magainin 2 as the length of the LPS polysaccharide moiety decreases . Disordering of the outer membrane lipid fatty acyl chains by magainin 2, however, depends primarily upon the magnitude of LPS charge rather than the length of the LPS polysaccharide, contradicting the proposal by Weiss et al . {Weiss, J., Beckerdite-Quagiata, S., & Elsbach, P . (1980) J . Clin . Invest . 65, 619-628} that the sugar side chain of LPS shields the negative charges of the outer membrane surface . While disruption of outer membrane structure most likely is not the primary factor leading to cell death, the susceptibility of Gram-negative cells to magainin 2 is associated with factors that facilitate the transport of the peptide across the outer membrane, such as the magnitude and location of LPS charge, the concentration of LPS in the outer membrane, outer membrane molecular architecture, and the presence or absence of the O-antigen side chain. FEMS Microbiol Lett, 1991 Jun 15, 65(2), 141 - 4 Transmembrane diffusion of hydrophobic antimicrobial agents and cell surface hydrophobicity in Bacteroides fragilis; Kobayashi Y et al.; The transmembrane diffusion of hydrophobic antimicrobial agents, e.g . lincomycin and clindamycin, was examined in Bacteroides fragilis which is sensitive to these agents . The results showed that these agents penetrate efficiently through the outer membrane . Cell surface hydrophobicity measured by the partition assay between water and p-xylene revealed that the cell surface of B . fragilis is more hydrophobic than that of Salmonella typhimurium or Pseudomonas aeruginosa . Furthermore, treatment with low concentrations of surfactant caused cell lysis . These results suggest that the cell surface hydrophobicity in B . fragilis plays an important role in the efficient transmembrane penetration of hydrophobic compounds . This efficiency explains the susceptibility of B . fragilis to hydrophobic antimicrobial agents. Res Microbiol, 1991 Jun, 142(5), 541 - 9 The activity in the chicken alimentary tract of bacteriophages lytic for Salmonella typhimurium; Berchieri A Jr et al.; Bacteriophages lytic for Salmonella typhimurium were isolated in considerable numbers from chickens experimentally infected with S . typhimurium, and in much lower numbers from the chicken feed . Lytic phages were also regularly isolated from human sewerage systems . One of these was used to inoculate S . typhimurium--infected two day-old chickens orally and via the feed . The phage took longer to establish in the caeca than did the Salmonella and it disappeared when the caecal S . typhimurium counts fell to 10(6) CFU/ml . No neutralizing antibodies to the phage were detected in the serum of these chickens . In a second experiment, five of 30 chickens similarly infected with S . typhimurium were inoculated with the phage . Within 3 days, the phage was isolated from 72% of the "in-contact" birds . A second phage, isolated from sewage, when inoculated into newly-hatched chickens simultaneously with any of 3 strains of S . typhimurium, produced a considerable reduction in mortality in the birds . This effect was only produced by inoculation of high concentrations of phage (greater than 10(10) PFU/ml) . The phage produced reductions in the viable numbers of S . typhimurium in the crop, small intestine and caeca for up to 12 h after inoculation, with smaller reductions in bacterial numbers in the liver at 24 and 48 h after infection. Am J Vet Res, 1991 Jun, 52(6), 833 - 7 Colonization control of lactose-fermenting Salmonella typhimurium in young broiler chickens by use of dietary lactose; Ziprin RL et al.; Inclusion of lactose in the diets of chickens has been determined to reduce cecal colonization with Salmonella typhimurium . We hypothesized, therefore, that dietary lactose may be a practical means for reducing the prevalence of Salmonella contamination of chicken products . Because some strains of Salmonella are atypical and ferment lactose, we investigated the effects of dietary lactose on cecal colonization with lactose-fermenting S typhimurium . Broiler chicks were inoculated intracloacally with Lac+ S typhimurium selected for resistance to novobiocin and rifampicin . The chicks also were inoculated orally with certain anaerobes that do not effectively inhibit colonization by S typhimurium, but do appear essential for lactose mediated inhibition of cecal colonization . Control chicks were not given dietary lactose, and chicks in the experimental group were fed a diet containing 7% lactose . Enumeration of Lac+ S typhimurium in cecal contents revealed dietary lactose to be effective at controlling this organism . Control was correlated with changes in cecal pH and increases in undissociated volatile fatty acids, especially propionic acid. J Mol Biol, 1991 Jun 5, 219(3), 471 - 80 Amino acids responsible for flagellar shape are distributed in terminal regions of flagellin; Kanto S et al.; The shape of the flagellar filaments of the bacterium Salmonella typhimurium under ordinary conditions is a left-handed helix . In addition to the normal wild-type filament, non-helical (i.e . straight), right-handed helical (early), or circular (semi-coiled and coiled) filaments and filament with small amplitude (fl-type) have been found in mutants or in filaments reconstituted in vitro . We analysed wild-type flagellin and flagellins from 17 flagellar-shape mutants (6 with straight filaments, 6 with curly filaments, 4 with coiled filaments and 1 with fl-type filament) by amino acid sequencing to identify the mutational sites . All mutant flagellins except that of the fl-type filament had single mutations; the fl-type flagellin had two mutations in the molecule . The sites of these mutations were localized in alpha-helical segments of the terminal regions of flagellin . A possible mechanism of the polymorphism of the flagellar filament is discussed. Trends Genet, 1991 Jun, 7(6), 196 - 200 Genetic analysis of the bacterial flagellum; Macnab RM et al.; Escherichia coli and Salmonella typhimurium invest considerable resources in making flagella, motor organelles that function much like the propellers on a ship . Both classical and molecular genetic studies have begun to reveal how flagellar genes are regulated and how their products build and operate these remarkable devices. Mutat Res, 1991 Jun, 252(3), 269 - 79 Optimum associations of tester strains for maximum detection of mutagenic compounds in the Ames test; Bonneau D et al.; The Ames test is now widely used as a short-term test for the detection of mutagens . Different strains are available with various genetic characteristics, and in the past decade various authors have recommended different associations of strains to give maximum detection potential . However, few studies have been done to compare the sensitivity of individual strains towards a wide range of compounds in a single study . In order to define the best association of strains for screening or regulatory purpose, we have tested 103 direct mutagens (reference genotoxins or in-house compounds) on 7 strains of Salmonella typhimurium: TA1535, TA1537, TA1538, TA97, TA98, TA100 and TA102 . 126 different associations of strains have been studied in terms of sensitivity and percentage overlap . Optimum associations of 2, 3, 4 or 5 strains included strains both with and without plasmid pKM101 . However, the specificity of detection is greatly diminished by the presence of plasmid pKM101 in the strain, as shown by the high degree of overlap in associations constituted entirely of strains containing the plasmid . The association of strains TA1538 and TA100 detected 86% of the chemicals tested and is therefore recommended for large-scale screening . A rate of detection of 100% was obtained when 6 strains were used . The best associations of 4 and 5 strains, which detected 97 and 99% chemicals respectively, all contained strains TA1537, TA1538 and TA102 . Finally, the associations of 4 strains (TA1537, TA1538, TA100, TA102) or 5 strains (TA1535, TA1537, TA1538, TA97, TA102) seemed well adapted to the optimum detection of mutagenic compounds. J Bacteriol, 1991 Jun, 173(12), 3894 - 900 Nucleotide sequences of the gnd genes from nine natural isolates of Escherichia coli: evidence of intragenic recombination as a contributing factor in the evolution of the polymorphic gnd locus; Bisercic M et al.; Nine natural isolates of Escherichia coli were examined, and the sequence of the entire 1,404 bases of the gnd gene (6-phosphogluconate dehydrogenase, EC 1.1.1.44) was determined . These isolates, along with E . coli K-12, constitute 10 strains for analysis . (The sequence of the E . coli K-12 gnd gene is known.) A total of 184 sites were polymorphic, and up to 6% sequence divergence was observed between pairs of strains . The deduced amino acid sequences showed much more variation than had been shown by multilocus enzyme electrophoresis, and in addition the net charge calculated did not correlate strongly with electrophoretic mobility . A phylogenetic tree for the sequences that was based on maximum parsimony differed significantly from a tree for the same strains that was based on multilocus enzyme electrophoresis for 35 enzymes (R . K . Selander, D . A . Caugant, and T . S . Whittam, p . 1625-1648, in F . C . Neidhardt, J . L . Ingraham, K . B . Low, B . Magasanik, M . Schaechter, and H . E . Umbarger, ed., Escherichia coli and Salmonella typhimurium: Cellular and Molecular Biology, 1987) . These data, together with analysis of sequence variation between the strains, indicated that intragenic recombination and transfer of the whole of gnd have occurred in the evolution of these strains . There is evidence of one recombination event between E . coli and Salmonella typhimurium. J Bacteriol, 1991 Jun, 173(12), 3695 - 9 Polyamines as constituents of the outer membranes of Escherichia coli and Salmonella typhimurium; Koski P et al.; Extraction of whole cells of Salmonella typhimurium and Escherichia coli with 1 M NaCl released 8 to 13% of their total cellular polyamines (putrescine, cadaverine, and spermidine) . This extraction did not cause significant cell lysis, release of outer membrane (OM) constituents, or leakage of periplasmic beta-lactamase . The extraction released nearly equal amounts of polyamines from mdo (membrane-derived oligosaccharide) mutants and wild type . These findings suggest that the released polyamines are apparently bound to the cell envelope . NaCl (1 M) was as effective as trichloroacetic acid in releasing polyamines from isolated OM and lipopolysaccharide (LPS) . Isolated OM contained four times more polyamines than the cytoplasmic membrane . The increased binding to the OM is apparently due to the association of polyamines with the polyanionic LPS . Nearly identical amounts of polyamines were found in the OM and LPS preparations (as quantified per milligram of LPS) . These amounts are equal to those released from the intact cells by 1 M NaCl (quantitation as above) . However, redistribution of polyamines took place after cell disruption, because the relative proportions of different polyamines varied in the OM and LPS preparations . These results indicate that polyamines released from intact cells during 1 M NaCl extraction are preferentially derived from the OM. J Bacteriol, 1991 Jun, 173(12), 3635 - 43 Mutant ribosomes can generate dominant kirromycin resistance; Tubulekas I et al.; Mutations in the two genes for EF-Tu in Salmonella typhimurium and Escherichia coli, tufA and tufB, can confer resistance to the antibiotic kirromycin . Kirromycin resistance is a recessive phenotype expressed when both tuf genes are mutant . We describe a new kirromycin-resistant phenotype dominant to the effect of wild-type EF-Tu . Strains carrying a single kirromycin-resistant tuf mutation and an error-restrictive, streptomycin-resistant rpsL mutation are resistant to high levels of kirromycin, even when the other tuf gene is wild type . This phenotype is dependent on error-restrictive mutations and is not expressed with nonrestrictive streptomycin-resistant mutations . Kirromycin resistance is also expressed at a low level in the absence of any mutant EF-Tu . These novel phenotypes exist as a result of differences in the interactions of mutant and wild-type EF-Tu with the mutant ribosomes . The restrictive ribosomes have a relatively poor interaction with wild-type EF-Tu and are thus more easily saturated with mutant kirromycin-resistant EF-Tu . In addition, the mutant ribosomes are inherently kirromycin resistant and support a significantly faster EF-Tu cycle time in the presence of the antibiotic than do wild-type ribosomes . A second phenotype associated with combinations of rpsL and error-prone tuf mutations is a reduction in the level of resistance to streptomycin. Mutat Res, 1991 Jun, 263(2), 93 - 100 Mutagenicity of (p-nitrophenyl)adenines in Salmonella typhimurium; Matsuda A et al.; Adenine derivatives having a p-nitrophenyl group at position 2, 8, or 9 were directly mutagenic towards Salmonella typhimurium strains TA98 and TA100, whereas N6-(p-nitrophenyl)adenine was not mutagenic . 2,9- And 8,9-bis-(p-nitrophenyl)adenines were also mutagenic, but N6,9-bis-(p-nitrophenyl)adenine was not . The study on 13 (p-nitrophenyl)adenine derivatives for their Salmonella mutagenicity indicates that only those having a p-nitrophenyl ring directly linked to the purine ring are mutagenic, implying the importance of the coplanar character of the nitrophenyl and the purine rings . The nitro group seems essential for the mutagenicity, as shown from the results of assays using nitroarene-sensitive and -insensitive Salmonella strains . The mutagenic potency of this class of compounds is high, comparable to that of 2-nitrofluorene. Carcinogenesis, 1991 Jun, 12(6), 1091 - 6 Azido- and nitro-PhIP, relatives of the heterocyclic arylamine and food mutagen PhIP--mechanism of their mutagenicity in Salmonella; Wild D et al.; Azido-PhIP (2-azido-1-methyl-6-phenylimidazo{4,5-b}pyridine) and nitro-PhIP (2-nitro-1-methyl-6-phenylimidazo{4,5-b}pyridine) have been synthesized and characterized chemically . The mutagenic potencies of azido-PhIP (with photoactivation by near UV irradiation), of nitro-PhIP (without exogenous activation) and of the heterocyclic amine PhIP (with activation by rat liver S9) were evaluated by means of the reversion assay in Salmonella typhimurium . Like PhIP, azido- and nitro-PhIP were potent mutagens in the strain TA98 . In addition to TA98, the strains YG1024 with increased and TA98/1,8-DNP6 deficient in acetyltransferase activity and TA98NR deficient in nitroreductase were used . Photolysis of azido-PhIP generates a very short-lived mutagen whose mutagenic potency is similar in all strains used and therefore not dependent on the acetyltransferase and nitroreductase . These findings are analogous to previous ones with azidofluorene and suggest that a short-lived DNA-binding arylnitrenium ion is formed directly by the photolysis of azido-PhIP . The nitroreductase contributes to the mutagenic potency of nitro-PhIP; in TA98NR it is 37% of that in TA98 . The acetylator status of the strains influences the mutagenic potencies of PhIP and nitro-PhIP only weakly . This contrasts with findings obtained with 2-amino-3-methylimidazo{4,5-f}quinoline (IQ) and nitro-IQ and with other amino- and nitro-imidazoarenes which lose most of their mutagenic activity in the acetyltransferase-deficient strain . This atypical behavior of PhIP suggests that the presumed metabolite, N-hydroxy-PhIP, differs from the N-hydroxy metabolites of other heterocyclic amino- and nitro-imidazoarenes in that in Salmonella it is not significantly activated by O-acetylation . It must therefore either react directly with DNA or be activated in a different way . This divergent behavior of PhIP and N-hydroxy-PhIP in Salmonella may also be a key to the understanding of several 'unusual' properties of PhIP in mammalian cells and organisms. Infect Immun, 1991 Jun, 59(6), 2158 - 65 Expression and immunogenicity of a streptococcal M protein epitope inserted in Salmonella flagellin; Newton SM et al.; A synthetic 48-bp oligonucleotide specifying the N-terminal 15 amino acids of M protein of Streptococcus pyogenes type 5 (plus a CTA codon, to terminate translation of genes with the insert in reverse orientation) was inserted by blunt-end ligation at the site of the 48-bp EcoRV deletion in the Salmonella flagellin gene in plasmid pLS408 (S . M . C . Newton, C . O . Jacob, and B . A . D . Stocker, Science 244: 70-72, 1989) . The resulting plasmid was transferred from Escherichia coli via a restriction-negative Salmonella typhimurium strain into an aromatic-compound-dependent, flagellin-negative live-vaccine strain of Salmonella dublin to produce strain SL7127, which was motile . Expression of the inserted epitope in flagellin and its exposure at the flagellar filament surface were shown by immunoblotting and by the reaction of flagellate bacteria (immobilization, immunogold labeling) with antibody raised by injection of the corresponding synthetic peptide, S-M5(1-15) . Rabbits immunized by injection of the live-vaccine strain with flagella composed of the chimeric flagellin or by injection of concentrated flagella from such bacteria developed antibodies reactive in an enzyme-linked immunosorbent assay with peptide S-M5(1-15) and with the large peptic-digest peptide pepM5 . These antibodies were opsonic for type 5 streptococci . Mice that were given parenteral live SL7127 (six doses, each 1 x 10(6) to 2 x 10(6), over 8 weeks) developed titers of ca . 12,800 for the M5-specific peptides and opsonizing activity for type 5 streptococci but not for type 24 streptococci . Sera from mice similarly immunized with a control live vaccine strain without an insert in the flagellin gene did not react with the M5-specific antigens . All of the five mice given the control strain, without an insert, died after challenge with type 5 streptococci or type 24 streptococci; by contrast, four of the five mice given strain SL7127, with an insert, survived the M5 challenge, but none of the five challenged with the type 24 strain survived . Therefore, our study shows that an M protein epitope can be expressed in the context of an unrelated protein and maintain its immunogenicity . Furthermore, we demonstrate that mice can be protected against a Streptococcus pyogenes type 5 challenge by immunization with a Salmonella live vaccine with flagella made of flagellin with an insert carrying a protective epitope of M5 protein but without the cross-reactive epitopes of the complete protein. Infect Immun, 1991 Jun, 59(6), 1954 - 60 Local skin response in mice induced by a single intradermal injection of bacterial lipopolysaccharide and lipid A; Ishikawa Y et al.; Dermal inflammation and hemorrhagic necrosis induced by bacterial lipopolysaccharide (LPS) and lipid A were studied in mice . In ddY mice, a single intradermal injection of Salmonella typhimurium S-form LPS and lipid A into the abdominal dermis elicited an edematous change due to an increase in local vascular permeability 12 h postinjection, followed by hemorrhagic necrosis from 24 to 72 h . This skin reaction was also induced in a dose-dependent manner by S-form LPS, R-mutant LPS, and lipid A of S . typhimurium and Escherichia coli, but not by polysaccharide from Salmonella S-form LPS . The dermal inflammation-inducing activities of LPS and lipid A were roughly in the following order (from highest to lowest): Re-form LPS, Rc-form LPS and lipid A, Ra-form LPS, and S-form LPS . These results suggest that the lipid A portion of the LPS molecule is responsible for the skin reaction . In C3H/HeN mice, Re-form LPS and lipid A induced the same intensity of skin reaction as that in ddY mice . In C3H/HeJ mice, which have a low response to LPS, Re-LPS and lipid A did not induce any hemorrhagic response but showed a distinct edematous change . Although hemorrhagic necrosis and edematous changes could be explained by quantitative differences in skin lesions, the other possible explanation is that hemorrhagic necrosis and the increase in local vascular permeability are induced by different mechanisms, only one of which depends on the regulation of the lps gene. J Immunol, 1991 Jun 1, 146(11), 3864 - 70 Mapping of the binding specificity for five monoclonal antibodies recognizing 3-deoxy-D-manno-octulosonic acid in bacterial lipopolysaccharides; Lind SM et al.; Mouse mAb were produced against the deep rough strains Salmonella minnesota R 595, Salmonella typhimurium SL 1102, and Escherichia coli D21f2 and screened by enzyme immunoassay against LPS of several chemotypes . Five antibodies were selected for their ability to bind to chemotype deep rough (Re) LPS which has two 3-deoxy-D-manno-octulosonic acid (Kdo) residues in its nonreducing end . Structurally verified oligosaccharides isolated from rough LPS and synthetic analogues of Kdo were used in an enzyme immunoassay inhibition test to determine the binding epitopes for the antibodies . According to their specificities, the antibodies could be divided into three groups . For two of the groups, the recognized structure was the alpha-Kdo (2----4) Kdo disaccharide and for one group the alpha-Kdo (2----4) alpha-Kdo beta-D-GlcN (1----6) alpha-D-GlcN tetrasaccharide, representing a partial structure of the Re LPS . Inhibition studies with synthetic analogues of Kdo showed that the anomeric configuration and the free carboxyl group of the Kdo residue are important features for antibody binding . Changes in the C-1 to C-6 region of the Kdo molecule do influence the antibody recognition considerably whereas changes in the exocyclic C-7 to C-8 region are of secondary importance . Calculation of the conformation of the inner core region showed that the alpha-Kdo (2----4) alpha-Kdo (2---- disaccharide was free and accessible in chemotype Re LPS, but that linkage of a L-glycero-D-manno-heptose to O-5 of the subterminal Kdo both changes the conformation of the Kdo-disaccharide and covers it thereby making it less accessible. Virology, 1991 Jun, 182(2), 673 - 81 A pilot protein participates in the initiation of P22 procapsid assembly; Thomas D et al.; The gene 16 protein of the bacteriophage P22 is required as a pilot protein aiding the transfer of DNA from the phage into the Salmonella typhimurium host cell . During assembly 10-20 copies of the 63,000-Da gp 16 protein are incorporated into the procapsid shell prior to DNA packaging . The protein has been purified from isolated procapsids and behaved as a monomer in solution . Upon incubation with purified coat and scaffolding subunits in vitro, it assembled into procapsids with the correct stoichiometry . The addition of physiological quantities of gp 16 resulted in an increased rate of procapsid assembly . Sedimentation of mixtures of coat and gp 16 protein subunits revealed association/dissociation behavior . It is likely that the added gp 16 is acting to stabilize a transient oligomeric coat protein species that functions as the in vitro initiation complex for procapsid assembly. Cell Immunol, 1991 Jun, 135(1), 88 - 94 Adoptive transfer of natural killer cell activity in B6D2F1 mice challenged with Salmonella typhimurium; Griggs ND et al.; The purpose of this study was to extend our previous findings as to the role of murine NK cells in host protection to a challenge infection with virulent Salmonella typhimurium SR-11 . B6D2F1 mice were depleted of NK cells with anti-asialo GM1 or a monoclonal antibody, anti-NK 1.1, followed by a salmonellae challenge . Significantly decreased numbers of splenic bacteria (P less than 0.005) in the NK cell-depleted mice were note at 12, 24, and 48 hr postchallenging, compared to the sham-injected control animals . When Percoll gradient-enriched large granular lymphocytes (NK cells) were adoptively transferred to NK cell-depleted mice followed by challenging, the splenic bacterial numbers were comparable to those present in NK cell-intact, control mice . These data indicate that large granular lymphocytes (NK cells) are responsible for the down-regulation of the protective host response in mice challenged with the facultative intracellular parasite . S . typhimurium. Eur J Clin Microbiol Infect Dis, 1991 Jun, 10(6), 486 - 90 Non-typhoid Salmonella bacteraemia in Greater Copenhagen 1984 to 1988; Lester A et al.; A retrospective survey of non-typhoid Salmonella bacteraemia in the period 1984 to 1988 was carried out by the five departments of clinical microbiology in Greater Copenhagen . A total of 168 patients were identified . A gradual increase was observed from 11 cases in 1984 to 58 cases in 1988 . The corresponding incidence per 100,000 inhabitants in Copenhagen rose from 0.9 in 1984 to 5.0 in 1988 . During the same period the total registered incidence of human Salmonella infections in Denmark increased from 17.6 to 67.4 per 100,000 inhabitants . The serotype most often isolated from bacteraemic patients was Salmonella dublin followed by Salmonella enteritidis and Salmonella typhimurium . Salmonella dublin demonstrated enhanced invasive and pathogenic properties . Predisposing factors were present in 56% of the patients; the most common was malignant disease . A fatal or complicated course of the bacteraemia was observed more frequently in patients with underlying diseases than in persons who had previously been healthy . A total of 17% of the patients died; one-fifth of these had a ruptured aortic aneurysm . It is concluded that the substantial increase in the number of cases and the often serious course taken by the infection demonstrate a need for increased efforts at prophylaxis. Can J Microbiol, 1991 Jun, 37(6), 474 - 7 Electrotransformation in Salmonella typhimurium LT2; Binotto J et al.; Electroporation gives high efficiency of transformation in Salmonella typhimurium LT2, yielding 10(8)-10(9) electrotransformants per microgram of pBR322 DNA . Lipopolysaccharide (LPS) composition has little influence on electrotransformation efficiency by electroporation, unlike Ca2+ shock methods, which give ca . 10(6) transformants/microgram DNA with strains with Rc or Rd2 LPS, 10(4) transformants with most smooth and rough strains, and 10(2) transformants with strains with Re LPS . Thus cell envelope properties are less crucial in electrotransformation than in Ca2+ shock methods . The reciprocal restriction barrier between Escherichia coli K-12 and S . typhimurium LT2 reduces electrotransformation by ca . 100-fold, but host-restriction mutants reduce or eliminate the barrier. J Cell Sci, 1991 Jun, 99 ( Pt 2), 283 - 96 Cytoskeletal rearrangements accompanying salmonella entry into epithelial cells; Finlay BB et al.; Salmonella bacteria can enter (invade) eukaryotic cells, and exist as intracellular parasites . Confocal, light immunofluorescence and electron microscopy were used to examine various cytoskeletal components of cultured Madin Darby canine kidney (MDCK) and HeLa epithelial cells after infection with Salmonella typhimurium . These bacteria entered and remained within membrane-bound vacuoles and were surrounded by large (5-10 microns) dense structures composed of various cytoskeletal components . These structures consisted of extensive aggregations of polymerized actin, alpha-actinin and tropomyosin above and beside the invading bacterium in both epithelial cell lines . These structures were evident soon after bacterial addition (maximal at 20 min for HeLa cells, 60 min for MDCK cells), and disappeared later in the infection as the cytoskeletal components returned to a more normal distribution after bacterial internalization . Surprisingly, tubulin also aggregated above internalized Salmonella although bacterial entry or penetration through polarized monolayers was not disrupted by the microtubule-inhibiting agent nocadazole (this treatment actually enhanced tubulin accumulation around these organisms) . There were little if any rearrangements in intermediate filaments composed of keratin or vimentin . Large amounts of talin also accumulated above and around invading Salmonella, but there was only a minor accumulation of vinculin around a few organisms . Pretreatment of epithelial cells with the microfilament inhibitor cytochalasin D blocked bacterial internalization but did not prevent accumulation of polymerized actin and alpha-actinin directly beneath uninternalized bacteria, yet prevented accumulation of the other cytoskeletal components . These results suggest that Salmonella bind to the surface and trigger a signal in epithelial cells that causes marked rearrangements in various cytoskeletal components, including recruitment of actin filaments and alpha-actinin, which then generates the force necessary for bacterial uptake. J Bacteriol, 1991 Jun, 173(12), 3663 - 72 Cloning and characterization of the Salmonella typhimurium ada gene, which encodes O6-methylguanine-DNA methyltransferase; Hakura A et al.; The ada gene of Escherichia coli encodes O6-methylguanine-DNA methyltransferase, which serves as a positive regulator of the adaptive response to alkylating agents and as a DNA repair enzyme . The gene which can make an ada-deficient strain of E . coli resistant to the cell-killing and mutagenic effects of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) has been cloned from Salmonella typhimurium TA1538 . DNA sequence analysis indicated that the gene potentially encoded a protein with a calculated molecular weight of 39,217 . Since the nucleotide sequence of the cloned gene shows 70% similarity to the ada gene of E . coli and there is an ada box-like sequence (5'-GAATTAAAACGCA-3') in the promoter region, we tentatively refer to this cloned DNA as the adaST gene . The gene encodes Cys-68 and Cys-320, which are potential acceptor sites for the methyl group from the damaged DNA . The multicopy plasmid carrying the adaST gene significantly reduced the frequency of mutation induced by MNNG both in E . coli and in S . typhimurium . The AdaST protein encoded by the plasmid increased expression of the ada'-lacZ chromosome fusion about 5-fold when an E . coli strain carrying both the fusion operon and the plasmid was exposed to a low concentration of MNNG, whereas the E . coli Ada protein encoded by a low-copy-number plasmid increased it about 40-fold under the same conditions . The low ability of AdaST to function as a positive regulator could account for the apparent lack of an adaptive response to alkylation damage in S . typhimurium. J Bacteriol, 1991 Jun, 173(12), 3609 - 14 Leakage of periplasmic enzymes from envA1 strains of Escherichia coli; Young K et al.; Previous work ascribed antibiotic hypersensitivity of the envA1 mutant to lowered lipopolysaccharide levels and exposure of the lipid bilayer . In the detailed characterization of the EnvA permeability phenotype presented here, the envA1 mutation was shown to confer leakage of the periplasmic enzymes beta-lactamase and RNase I . Leakage was observed in three different genetic backgrounds, including the original envA1 strain and its parent . In contrast, no detectable leakage of the cytoplasmic enzyme beta-galactosidase was observed . Sensitivity of envA1 strains to a range of antibiotics not previously reported was tested, and lipophilicity (partition coefficient) of a number of antibiotics was determined . On the basis of observations of periplasmic leakage and sensitivity to large hydrophilic antibiotics and lysozyme, part of the permeability phenotype of the envA1 mutant is proposed to be due to transient rupture and resealing of the EDTA-sensitive outer membrane layer . In this regard, the EnvA permeability phenotype falls into a general class of permeability/leaky mutants of both Escherichia coli and Salmonella typhimurium. J Bacteriol, 1991 Jun, 173(11), 3587 - 90 DNA damage-inducible loci in Salmonella typhimurium; Smith CM et al.; lac operon fusions to DNA damage-inducible (din) loci were generated in Salmonella typhimurium LT2 . Many of these din fusions were efficiently repressed by cloned Escherichia coli LexA, while others were not; all required RecA for induction . Several din fusions exhibited strong inducibility and will be useful in developing an SOS induction assay in S . typhimurium to detect genotoxins. J Bacteriol, 1991 Jun, 173(11), 3584 - 6 Properties of the Bacillus subtilis chemotaxis protein CheF, a homolog of the Salmonella typhimurium flagellar protein FliJ; Ying CW et al.; The nucleotide sequence of Bacillus subtilis cheF was corrected . It encodes an 18-kDa protein that is homologous to FliJ, a protein required for formation of basal bodies in Escherichia coli and Salmonella typhimurium . Methanol release is abnormal in cheF mutants, suggesting that the morphology and functioning of the motor affects methanol formation. J Bacteriol, 1991 Jun, 173(11), 3554 - 8 Cloning and nucleotide sequence of the anaerobically regulated pepT gene of Salmonella typhimurium; Miller CG et al.; The anaerobically regulated pepT gene of Salmonella typhimurium has been cloned in pBR328 . Strains carrying the pepT plasmid, pJG17, overproduce peptidase T by approximately 70-fold . The nucleotide sequence of a 2.5-kb region including pepT has been determined . The sequence codes for a protein of 44,855 Da, consistent with a molecular weight of approximately 46,000 for peptidase T (as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration) . The N-terminal amino acid sequence of peptidase T purified from a pJG17-containing strain matches that predicted by the nucleotide sequence . A plasmid carrying an anaerobically regulated pepT::lacZ transcriptional fusion contains only 165 bp 5' to the start of translation . This region contains a sequence highly homologous to that identified in Escherichia coli as the site of action of the FNR protein, a positive regulator of anaerobic gene expression . A region of the deduced amino acid sequence of peptidase T is similar to segments of Pseudomonas carboxypeptidase G2, the E . coli peptidase encoded by the iap gene, and E . coli peptidase D. J Bacteriol, 1991 Jun, 173(11), 3547 - 53 The metR binding site in the Salmonella typhimurium metH gene: DNA sequence constraints on activation; Byerly KA et al.; Transcription of the metH gene in Salmonella typhimurium and Escherichia coli is positively regulated by the metR gene product, a DNA binding protein . The interaction between the MetR activator protein and the S . typhimurium metH control region was investigated . In vitro gel mobility shift assays and DNase I protection assays established that the MetR protein binds to and protects a 24-bp sequence in the metH promoter region from DNase I attack . This region includes the proposed metR recognition sequence 5'-TGAANNNNNCTCA-3' . Single-base-pair changes were introduced into the proposed MetR recognition sequence within the promoter region of a metH-lacZ gene fusion by oligonucleotide-directed mutagenesis . Two classes of mutations were identified . In the first class, the mutations caused reduced activation of the metH-lacZ fusions that correlated with reduced MetR binding . In the second class, activation of the metH-lacZ fusion was reduced, yet there was no appreciable reduction in MetR binding, indicating that the presence of bound MetR is not sufficient for activation of metH-lacZ gene expression . These two classes of mutations in the DNA binding site are grouped spatially, suggesting that the proposed MetR recognition sequence can be divided into two functional domains, one for binding and the other for activation. Poult Sci, 1991 Jun, 70(6), 1448 - 51 Research note: use of consecutive carcass rinses and a most probable number procedure to estimate salmonellae contamination of inoculated broilers; Izat AL et al.; Two similar trials were conducted to evaluate the accuracy of the whole carcass rinse technique in combination with a most probable number (MPN) procedure for estimating the number of salmonellae on postchill broilers . Birds were reared in litter-floored pens and inoculated with Salmonella typhimurium (10(8) cfu/mL) on Days 2, 7, and 14 . In each of the two trials six carcasses were consecutively rinsed four times . Each carcass was rinsed with 100 mL of sterile water in sterile plastic bags using an automated shaking device . Salmonellae were enumerated using a three-tube MPN procedure in selenite cystine broth . There were no statistical differences in log10 MPN salmonellae per milliliter of recovered rinse fluid due to trial or consecutive rinse . In several cases salmonellae were not recovered in the initial rinse but were recovered from consecutive rinses of the same carcass . A large amount of variation in MPN levels of salmonellae among individual carcasses occurred within each consecutive rinse . The data suggested that only a percentage of the total salmonellae present on a postchill carcass were recovered with each consecutive rinse, and the organisms were firmly attached prior to processing. Poult Sci, 1991 Jun, 70(6), 1438 - 40 Research note: incidence, number, and serotypes of Salmonella on frozen broiler chickens at retail; Izat AL et al.; Two similar trials were conducted to evaluate broiler carcasses at retail for incidence, number, and serotypes of salmonellae . Twelve frozen carcasses were purchased from each of three retail outlets on two sampling days . Two of the brands purchased were produced and processed conventionally, but the third brand was produced and processed under organic conditions . The frozen carcasses were tempered to 4.4 C prior to microbiological sampling . All carcasses were sampled using a mechanical shaker and 100 mL of sterile water . Recovered rinse fluid was evaluated for levels of salmonellae using a three-tube most probable number technique . All recovered Salmonella isolates were serotyped using the Kauffmann-White scheme . Incidence rates across the three brands ranged from 17 to 50%, with most probable number of salmonellae per 100 mL of recovered rinse fluid ranging from 5 to 34 organisms . Serotypes recovered include Salmonella typhimurium, Salmonella paratyphi, and Salmonella arizonae. Mol Microbiol, 1991 Jun, 5(6), 1375 - 83 A chimeric nucleotide-binding protein, encoded by a hisP-malK hybrid gene, is functional in maltose transport in Salmonella typhimurium; Schneider E et al.; We have isolated a hybrid gene, composed of the first 455 nucleotides of hisP and nucleotides 275-1107 of malK, the genes coding for the nucleotide-binding components of the high-affinity transport systems for histidine and maltose in Salmonella typhimurium, respectively . The fusion had occurred by recombination within 11 homologous base pairs located between the two DNA fragments . In the chimeric protein peptidic motifs A and B, proposed to be part of the nucleotide-binding fold, originate from HisP and MalK, respectively . Plasmid pES42-39, harbouring the hybrid gene, was shown to complement only a malK mutation but failed to complement a hisP deletion mutation . The chimeric protein was identified by immunoblotting as a protein with an apparent molecular mass of 49kDa . Removal of the C-terminal 77 amino acid residues from the chimeric protein resulted in the loss of function in transport . In contrast, 51 amino acid residues could be removed from the C-terminus of wild-type MalK without any effect . Upon overproduction the chimeric protein, as wild-type MalK, inhibited expression of the malB regulon . However, both truncated proteins, when overproduced, did not exhibit this activity . Based on these results, a tentative model of the functional domains of MalK is presented. Mol Microbiol, 1991 Jun, 5(6), 1337 - 45 Analysis of an anaerobically induced promoter for the cobalamin biosynthetic genes in Salmonella typhimurium; Richter-Dahlfors AA et al.; We have identified an anaerobically induced promoter for the cobalamin biosynthetic (cob) genes . In a plasmid the Cob promoter showed two of the three types of control of the intact chromosomal Cob operon: anaerobic induction and cAMP stimulation . Cobalamin repression was observed only in promoter fragments which included sequences far downstream of the transcription start site, suggesting that this control is post-transcriptional . One anaerobically induced transcript was identified and its 5' end was determined . Deletion mapping showed that 60 nucleotides upstream of the start site were sufficient for anaerobic synthesis of this transcript . Upstream of the transcription start site a putative sigma 70-dependent -10 recognition sequence was identified; however, no consensus -35 region was observed. Microb Pathog, 1991 Jun, 10(6), 493 - 9 Tn5 mutagenesis of the Salmonella typhimurium 100 kb plasmid: definition of new virulence regions; Sizemore DR et al.; In this study, the 100 kb plasmid of Salmonella typhimurium, which is known to contribute to the pathogenicity of the organism, was tagged with the transposon Tn5 to define regions of the plasmid contributing to overall virulence . Eleven randomly selected vir::Tn5 plasmids carried by the plasmid-free S . typhimurium strain WS1321 were physically mapped and then examined in mice for subcutaneous LD50 value, ability to induce splenomegaly, and ability to grow to high numbers in the spleens of infected mice . Nine strains were found to be virulence-attenuated and showed varied levels of growth in the spleens of subcutaneously infected BALB/c mice . Eight of these nine strains carried Tn5 insertions which lie outside the previously defined virulence region . These studies corroborate the findings of other investigators as well as defining novel regions of the 100 kb virulence plasmid involved in the pathogenicity of this organism. Antimicrob Agents Chemother, 1991 Jun, 35(6), 1203 - 7 Increased susceptibility to beta-lactam antibiotics and decreased porin content caused by envB mutations of Salmonella typhimurium; Oppezzo OJ et al.; Isogenic derivatives carrying envB6, envB9, or envB+ alleles were obtained from a strain of Salmonella typhimurium that was partially resistant to mecillinam, a beta-lactam antibiotic specific for penicillin-binding protein 2 (PBP 2) . Testing of the isogenic strains with several antibacterial agents demonstrated that envB mutations either increased resistance (mecillinam) or did not affect the response (imipemen) to beta-lactams that act primarily on PBP 2, while susceptibilities to beta-lactams that act on PBP 1B, PBP 3, or both were increased . Furthermore, the susceptibilities of envB strains to hydrophobic compounds such as rifampin, novobiocin, or chloramphenicol were not modified, even though their susceptibilities to deoxycholate and crystal violet were enhanced . Outer cell membranes of envB mutants presented a 50% reduction in protein content compared with that of the isogenic envB+ strains, and OmpF and OmpD porins were particularly affected by the reduction . No alteration in the amount or pattern of periplasmic proteins was noticed, and lipopolysaccharides from envB mutants appeared to be normal by sodium dodecyl sulfate-urea-polyacrylamide gel electrophoresis . By using derivatives that produced a plasmid-encoded beta-lactamase, it was demonstrated that envB cells are slightly less permeable to cephalothin than envB+ bacteria are . It is concluded that the high susceptibility of envB mutants to beta-lactams is due to the increased effectiveness of the antibiotics on PBP 1B, PBP 3, or both. Electrophoresis, 1991 Jun, 12(6), 448 - 50 Alteration in the electrophoretic mobility of OmpC due to variations in the ammonium persulfate concentration in sodium dodecyl sulfate-polyacrylamide gel electrophoresis; Lobos SR et al.; Studies on Salmonella typhi and Salmonella typhimurium outer membrane proteins have shown that the relative position of OmpC porin in sodium dodecyl sulfate.polyacrylamide gel electrophoresis undergoes an important shift when the concentration of ammonium persulfate in the running gel is increased from 6 to 12 mM . The apparent molecular mass at these concentrations was estimated to be 34 and 40 kDa, respectively . Under similar electrophoretic conditions the apparent molecular mass estimated for OmpF was 37.6 and 38.2 kDa . Therefore, OmpC moves from a leading position to a position behind OmpF . For Escherichia coli OmpC the shift observed is less pronounced than that occurring in Salmonellae. J Bacteriol, 1991 Jun, 173(11), 3564 - 72 Salmonella typhimurium mutants defective in flagellar filament regrowth and sequence similarity of FliI to F0F1, vacuolar, and archaebacterial ATPase subunits; Vogler AP et al.; Many flagellar proteins are exported by a flagellum-specific export pathway . In an initial attempt to characterize the apparatus responsible for the process, we designed a simple assay to screen for mutants with export defects . Temperature-sensitive flagellar mutants of Salmonella typhimurium were grown at the permissive temperature (30 degrees C), shifted to the restrictive temperature (42 degrees C), and inspected in a light microscope . With the exception of switch mutants, they were fully motile . Next, cells grown at the permissive temperature had their flagellar filaments removed by shearing before the cells were shifted to the restrictive temperature . Most mutants were able to regrow filaments . However, flhA, fliH, fliI, and fliN mutants showed no or greatly reduced regrowth, suggesting that the corresponding gene products are involved in the process of flagellum-specific export . We describe here the sequences of fliH, fliI, and the adjacent gene, fliJ; they encode proteins with deduced molecular masses of 25,782, 49,208, and 17,302 Da, respectively . The deduced sequence of FliI shows significant similarity to the catalytic beta subunit of the bacterial F0F1 ATPase and to the catalytic subunits of vacuolar and archaebacterial ATPases; except for limited similarity in the motifs that constitute the nucleotide-binding or catalytic site, it appears unrelated to the E1E2 class of ATPases, to other proteins that mediate protein export, or to a variety of other ATP-utilizing enzymes . We hypothesize that FliI is either the catalytic subunit of a protein translocase for flagellum-specific export or a proton translocase involved in local circuits at the flagellum. J Biol Chem, 1991 May 25, 266(15), 9857 - 65 The membrane-bound proteins of periplasmic permeases form a complex . Identification of the histidine permease HisQMP complex; Kerppola RE et al.; The membrane-bound proteins of periplasmic transport systems have been hypothesized to form a complex with relatively little experimental support . Here we present experimental evidence that HisQ, HisM, and HisP, the membrane-bound proteins of the periplasmic histidine transport system of Salmonella typhimurium, form such a complex . We have developed antibodies specific to each of these proteins to aid in their characterization . Extractions with urea, alkaline pH, or Triton X-114 show that HisQ and HisM are integral membrane proteins . By these tests HisP displays an unusual behavior, being associated with the membrane whether or not HisQ and HisM are present and despite its hydrophilic sequence . However, the nature of HisPs interaction with the membrane is shown to vary depending on the presence of HisQ and HisM . In their absence, HisP is somewhat peripherally associated with the membrane, while in their presence it binds much more tightly, indicating that it forms a complex in association with HisQ and HisM . This is demonstrated by the coimmunoprecipitation of all three proteins by antibodies directed against any one of them . Chemical cross-linking allowed the characterization of the subunit stoichiometry of the complex as two HisPs to one HisQ and one HisM . Within this complex all three proteins probably contact each other and the two HisPs form a dimer . We hypothesize that HisQ and HisM with their multiple membrane-spanning segments form a "channel" within which the HisP subunits are located. J Biol Chem, 1991 May 25, 266(15), 9673 - 7 Determination of a region of the HisJ binding protein involved in the recognition of the membrane complex of the histidine transport system of Salmonella typhimurium; Prossnitz E; Site-directed mutagenesis has been utilized to examine the nature of the interaction of the histidine-binding protein (HisJ) with the membrane-bound components of the histidine transport system . In order to examine a region of the HisJ protein involved in the interaction with the membrane components, a number of charged amino acids in the vicinity of the genetically isolated interaction mutant hisJ5625 (R176C) were mutated . It was found that residues Asp171, Arg176, and Asp178 could be independently altered without affecting the histidine-binding affinity of the HisJ protein . However, the alteration of residues Asp171 and Arg176 greatly reduced the interaction of the HisJ protein with the membrane protein complex, whereas altering residue Asp178 had no effect on this interaction . Simultaneously, altering residues Asp183 and Glu184 resulted in a completely defective protein . The ability of a his-J5625 suppressor HisP protein (HisP(T205A)) to suppress the newly created site-directed mutants was also examined . This suppressor demonstrated specificity toward the amino acid present at position 176 and was also able the suppress the mutation created at position 171. Gene, 1991 May 15, 101(1), 23 - 31 Gene-protein relationships in the flagellar hook-basal body complex of Bacillus subtilis: sequences of the flgB, flgC, flgG, fliE and fliF genes; Zuberi AR et al.; The nucleotide sequence of five genes from the major Bacillus subtilis chemotaxis locus has been determined . Four of these genes encode proteins that are homologous to the Salmonella typhimurium FlgB, FlgC, FlgG and FliF proteins . One gene encodes a protein that is homologous to the Escherichia coli FliE protein . The data from S . typhimurium and E . coli suggest that all of these proteins form part of the hook-basal body (HBB) complex of the bacterial flagella . The FlgB, FlgC and FlgG proteins are components of the proximal and distal rods . The FliF protein forms the M-ring that anchors the rod assembly to the membrane . The role of the FliE protein within the HBB complex has not yet been determined . The similarity between the B . subtilis and S . typhimurium proteins suggests that the structure of the M-ring and the rod may be similar in the two species . However, we observed some differences in size and amino acid composition between some of the corresponding homologues that suggest the basal body proteins may be organized slightly differently within B . subtilis. Chem Res Toxicol, 1991 May-Jun, 4(3), 334 - 40 1,3-Dialkyltriazenes: reactive intermediates and DNA alkylation; Kroeger-Koepke MB et al.; The reactions of calf thymus (ct) DNA with 1,3-dimethyltriazene (DMT), N-methyl-N-nitrosourea (MNU), 1,3-diethyltriazene (DET), N-ethyl-N-nitrosourea (ENU), and 1-ethyl-3-methyltriazene (MET) were studied as a function of concentration of the alkylating agents, of various buffers, and of ionic strength . The amount of alkylation at the 7- and O6-positions of guanine increased linearly with dose over a 10-fold concentration range . The slopes of the DMT and MNU curves were identical as were those of DET and ENU . These data suggest that both types of compounds alkylate DNA via a similar intermediate, presumably the corresponding alkanediazonium ion . MET methylates and ethylates DNA, the amount of each product being a function of the competitive formation of the two diazonium ions possible from MET . The MET product ratios could be reproduced by an appropriate mixture of DET and DMT . The alkylation of DNA by DMT and by MET is very sensitive to ionic strength, to the nature of the buffer, and to the identity of the salt used to balance ionic strength . In general, the reaction is favored by low ionic strength, by amine rather than oxy acid buffers, and by doubly charged inert anions . The alkylation of DNA is inversely proportional to the logarithm of the ionic strength over a wide range . The mutagenic activity of triazenes in Salmonella typhimurium is correlated very well with the ability of the triazenes to form adducts, particularly O6-guanine adducts.(ABSTRACT TRUNCATED AT 250 WORDS) J Biol Chem, 1991 May 5, 266(13), 8328 - 35 Identification of amino acid residues involved in feedback regulation of the anthranilate synthase complex from Salmonella typhimurium . Evidence for an amino-terminal regulatory site; Caligiuri MG et al.; The anthranilate synthase-phosphoribosyl transferase complex, a heterotetrameric enzyme made up of the TrpE and TrpD polypeptides, catalyzes three reactions comprising the first two steps of tryptophan biosynthesis in Salmonella typhimurium . All three activities of the complex are subject to feedback inhibition by tryptophan, which results from allosteric effects associated with the binding of one molecule of inhibitor to each of the TrpE subunits of the complex . Random in vitro chemical mutagenesis of the trpE gene was used to generate a collection of mutant forms of the complex which displayed varying degrees of resistance to feedback inhibition . Single amino acid substitutions, identified by DNA sequencing, were found at 14 different residues within the TrpE polypeptide . The residues were distributed throughout TrpE, but those that appeared to be most critical for regulation were found in two clusters, one at the extreme amino-terminal end, including residues Glu-39, Ser-40, and Ala-41, and the other in the middle of the polypeptide, including residues Asn-288, Pro-289, Met-293, Phe-294, and Gly-305 . Kinetic and binding studies of the purified mutant complexes demonstrated that 9 of the 14 had a marked decrease in affinity for tryptophan with little or no change in substrate affinity or catalytic capacity . The remaining five enzymes exhibited more subtle changes, having small decreases in inhibitor affinity coupled with small increases in substrate affinity . Mutant enzymes that were not totally feed-back-resistant had a decreased kinetic response to tryptophan binding . All enzymes exhibited alterations in tryptophan-induced conformational changes as monitored by dye-ligand chromatography. J Biol Chem, 1991 May 5, 266(13), 8348 - 54 Roles of the highly conserved aspartate and lysine residues in the response regulator of bacterial chemotaxis; Lukat GS et al.; The chemotactic responses of bacteria such as Escherichia coli and Salmonella typhimurium are mediated by phosphorylation of the CheY protein . Phospho-CheY interacts with the flagellar motor switch to cause tumbly behavior . CheY belongs to a large family of phosphorylated response regulators that function in bacteria to control motility and regulate gene expression . Residues corresponding to Asp57, Asp13, and Lys109 in CheY are highly conserved among all of these proteins . The site of phosphorylation in CheY is Asp57, and in the three-dimensional structure of CheY the Asp57 carboxylate side chain is in close proximity to the b