Mol Gen Genet, 1996 Oct 16, 252(5), 626 - 9 The nadB gene of Salmonella typhimurium complements the nicotinic acid auxotrophy of Shigella flexneri; Mantis NJ et al.; Shigella species are characteristically nicotinic acid (NA) auxotrophs . The invasive S . flexneri strain M90T, transformed with the multicopy plasmid pZT349 encoding the nadB gene of Salmonella typhimurium, can grow in minimal glucose medium without exogenous NA, whereas, M90T containing the control vector, pUC18 does not, suggesting that this species lacks L-aspartic acid oxidase, the first enzyme in the de novo NAD biosynthetic pathway . The estimated growth rate of strain M90T (pZT349) in HeLa cells was identical to that of M90T (pUC18), indicating the available intracellular concentration of NA is not limiting for bacterial growth. Commun Dis Rep CDR Rev, 1996 Oct 11, 6(11), R159 - 62 An outbreak of Salmonella typhimurium DT104 food poisoning associated with eating beef; Davies A et al.; An outbreak of Salmonella typhimurium DT104 infection in Shropshire in May 1995 was identified when four isolates were noted to be from members or supporters of a local football team that had held several social functions in the same week . The subsequent investigation identified 16 people with gastrointestinal symptoms and 12 with microbiologically confirmed infection . The outbreak was complex, associated with several social functions on different days, but infection was associated with eating beef at a public house . A number of errors were detected in the cooking, storage, and handling of the implicated food . The investigation identified beef as the vehicle of infection in this outbreak but was unable to show whether it was the original source of infection or whether cross or manual contamination occurred in the kitchen. Commun Dis Rep CDR Rev, 1996 Oct 11, 6(11), R155 - 9 Epidemiological application of differentiating multiresistant Salmonella typhimurium DT104 by plasmid profile; Threlfall EJ et al.; Human isolates of multiresistant Salmonella typhimurium definitive phage type (DT) 104 in England and Wales are currently second in number only to those of S . enteritidis phage type 4 . Differentiation of strains is essential in epidemiological investigations and the value of one method, plasmid profile typing, has been assessed in a study of 600 isolates of S . typhimurium DT 104 with multiresistant antibiograms (R-types) ACSSuT, ACSSuTCp and ACSSuTTm from humans, food animals, human food, pets, and animal feed made in England and Wales from January 1990 to April 1996 . Twenty plasmid profile (PP) types have been identified in isolates of R-type ACSSuT and ACSSuTCp . One profile type, with a single plasmid of 60 megadaltons-PP type A-has predominated, but identification of PP type has proved useful in some epidemiological investigations . A further four PP types have been identified in isolates of DT 104 R-type ACSSuTTm, in which resistance to trimethoprim is encoded by a plasmid of 4.6 megadaltons and the two commonest PP types are related to those also common in DT 104 R-type ACSSuT . Methods of differentiating within the commonest profile type are now needed. Gene, 1996 Oct 10, 175(1-2), 23 - 7 A Shigella flexneri invasion plasmid gene, ipgH, with homology to IS629 and sequences encoding bacterial sugar phosphate transport proteins; Venkatesan MM et al.; Sequences representing the 2684 bp flanking the ipaH4.5 gene on the invasion plasmid of Shigella flexneri 5 indicate an unusual fusion gene, designated ipgH, in which the first 27 amino acids (aa) are identical to ORF2 of IS629 . The aa sequence encoded by the remainder of ipgH bears significant homology to Escherichia coli and to Salmonella typhimurium GlpT and UhpT proteins and to the S . typhimurium PgtP protein, which are involved in the uptake of high-energy sugar phosphates from an external source. Eur J Pharmacol, 1996 Oct 10, 313(1-2), 129 - 34 Tolerance to lipopolysaccharide-induced increase in vascular permeability in mouse skin; Fujii E et al.; We investigated whether tolerance develops to the lipopolysaccharide-induced increase in vascular permeability of mouse skin on pretreatment with Salmonella typhimurium lipopolysaccharide . Lipopolysaccharide-induced plasma extravasation was assessed by determining Pontamine sky blue dye accumulation in the skin where lipopolysaccharide was injected s.c . 2 h previously . When mice were pretreated with lipopolysaccharide (0.15 mg/kg i.p.), the dye leakage induced by s.c . challenge with lipopolysaccharide (400 micrograms/site) was significantly, inhibited for 2-24 h after pretreatment, indicating the development of lipopolysaccharide tolerance . At 4 h after lipopolysaccharide (0.15 mg/kg i.p.), the dose-response curve of dye leakage against the challenge dose of lipopolysaccharide shifted about 2-fold to the higher dose . The dye leakage induced by lipopolysaccharide was inhibited by pretreatment with lipopolysaccharide in a dose-dependent manner (0.05-0.15 mg/kg i.p.) . Lipopolysaccharide tolerance was not seen in adrenalectomized mice . When mice were pretreated with lipopolysaccharide and NG-nitro-L-arginine methyl ester (L-NAME), a nitric oxide (NO) synthase inhibitor, at the same time, the hyporesponsiveness to lipopolysaccharide challenge disappeared . However, L-NAME was ineffective to inhibit the development of lipopolysaccharide tolerance when administered 24 h after lipopolysaccharide pretreatment or just before the lipopolysaccharide challenge . Tumor necrosis factor-alpha and interleukin-1 alpha but not interleukin-6 induced a similar hyporesponsiveness to lipopolysaccharide . These results suggest that tolerance develops to the lipopolysaccharide-induced increase in vascular permeability in mouse skin after a single lipopolysaccharide administration and that endogenous glucocorticoids and NO are necessary for induction of lipopolysaccharide tolerance . Hyporesponsiveness induced by lipopolysaccharide pretreatment may be mediated by production of some cytokines such as tumor necrosis factor-alpha or interleukin-1 alpha. Genetika, 1996 Oct, 32(10), 1333 - 40 {Specificity and time of the appearance of His+ reversions induced by histidine starvation in Salmonella typhimurium}; Gizatullin FSh et al.; It was previously established that reversion of the hisG46 allele of Salmonella typhimurium to prototrophy occurred upon histidine starvation . In this paper, it was shown that histidine starvation does not affect the appearance of mutants resistant to L-arabinose and rifampicin . Threonine starvation did not change the frequency of His+ revertants . Analysis of His+ revertant clones did not reveal additional L-arabinose resistance mutations . Thus, these experiments allowed the conclusion that amino acid starvation does not lead to a nonspecific increase in the mutation rate . In addition, it was shown that spontaneous His+ revertants start to arise after two to three hours of histidine starvation, this process lasting for four days . Nevertheless, original His+ cells did not grow in a culture generating His+ revertants . Traces of histidine and novobiocin added to a minimal medium retarded reversion realization . However, the occurrence of revertants was not markedly inhibited by chloramphenicol . Based on the results, it is assumed that adaptive His+ reversions occurred due to a special mode of replication induced upon histidine starvation and requiring no de novo protein synthesis. Vaccine, 1996 Oct, 14(14), 1384 - 90 Delivery of the Pertactin/P.69 polypeptide of Bordetella pertussis using an attenuated Salmonella typhimurium vaccine strain: expression levels and immune response; Anderson R et al.; Pertactin/P.69, a surface-associated polypeptide antigen of Bordetella pertussis, was expressed in a Salmonella typhimurium aroA aroD vaccine strain, BRD509, using different expression systems, and the immune response in mice against these constructs was compared . Initially, Pertactin/P.69 was expressed on the surface of BRD509 from a single copy of the gene encoding the antigen localized on the Salmonella chromosome . As previously shown, secretory and humoral antibody responses could not be detected following multiple immunization with this strain (BRD640) . However, a strong anti-Pertactin/P.69 proliferative response was observed in murine splenocytes following a single oral dose with BRD640 . The stimulated splenocytes secreted interferon-gamma but not interleukin-5, indicating that BRD640 induced a Th1 type T-helper response against Pertactin/P.69 . We wished to construct a vaccine strain that might induce secretory and humoral responses against Pertactin/P.69 as well as a cell-mediated immune response . Consequently, Pertactin/P.69 was expressed at high levels in the cytoplasm of BRD509 under the control of the inducible nirB promoter from a ColE1-based replicon . Anti-Pertactin/P.69 immune responses were not observed following immunization of BALB/c mice with this strain (BRD975) . Priming of the immune system against Pertactin/P.69 was, however, observed following oral immunization with BRD975 and boosting subcutaneously with purified Pertactin/P.69 antigen . The major anti-Pertactin/P.69 IgG subclass detected in boosted mice was IgG2a; thus, as BRD640, BRD975 appeared to induce a Th1 type T-helper response against Pertactin/P.69. Avian Dis, 1996 Oct-Dec, 40(4), 924 - 6 Effect of ochratoxin A on Salmonella typhimurium-challenged layer chickens; Fukata T et al.; Eleven-day-old chickens received 10(8) colony-forming units Salmonella typhimurium orally for 2 consecutive days . The next day, the 13-day-old chickens were given a high dose of ochratoxin A (3 mg/kg) orally . The number of S . typhimurium in both the duodenal and cecal contents of chickens administered with high doses of ochratoxin A increased significantly when compared with control birds . Ochratoxin A was shown to be one of numerous factors that affect the susceptibility of chickens to salmonellae colonization. APMIS, 1996 Oct, 104(10), 750 - 4 Immunity to experimental Salmonella typhimurium infections in rats . Transfer of immunity with primed CD45RC+ and CD45RC- CD4 T-cell subpopulations; Thygesen P et al.; The protective effect of primed CD4 T cells against a lethal dose of Salmonella typhimurium was studied in Lewis rats . Primed CD4 T cells were obtained by inoculating Lewis rats with a non-lethal dose of S . typhimurium . Four weeks after the infection, spleen CD4 T cells were separated by antibody-coated magnetic microspheres using an antibody against the CD4 molecule (W3/25) . The cells were separated according to their expression of the CD45RC isoform of the leukocyte common antigen by FACS . CD45RC+ and CD45RC- CD4 T-cell subpopulations were transferred to untreated rats 24 h prior to infection with S . typhimurium . Transfer of CD45RC+ and CD45RC- CD4 T cells induced a significant survival, p = 0.022 and p = 0.023 respectively, following inoculation with S . typhimurium compared to animals with no cells transferred . The infection induced an increase in CD4 T cells expressing the CD45RC isoform compared to untreated controls (p < 0.001) . It is concluded that both CD45RC+ and CD45RC- cells can induce a significant protection against S . typhimurium infections in rats . Therefore the CD45RC antigen cannot be used as a phenotypic marker for functionally distinct CD4 T-cell subpopulations . The infection-induced increase in CD45RC+ cells is most likely due to generation of antigen-specific memory T cells. Regul Toxicol Pharmacol, 1996 Oct, 24(2 Pt 2), S261 - 3 Mutagenicity studies on erythritol in bacterial reversion assay systems and in Chinese hamster fibroblast cells; Kawamura Y et al.; The sweetener erythritol tested negative in reverse mutation assays using Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537 and the WP2 uvrA strain of Escherichia coli . Erythritol tested negative in chromosome aberration tests using the Chinese hamster fibroblast cell line CHL/IU. Arzneimittelforschung, 1996 Oct, 46(10), 972 - 5 Assessment of genotoxic effect of piperine using Salmonella typhimurium and somatic and somatic and germ cells of Swiss albino mice; Karekar VR et al.; Piperine (CAS 94-62-2) is a constituent of various spices and is used as a common food additive all over the world . The genotoxic potential of piperine was assessed using four different test systems, namely, Ames test using Salmonella typhimurium, micronucleus test, sperm shape abnormality test and dominant lethal test using Swiss albino mice . In the Ames test, six different doses of piperine, in the range of 0.005-10 mumol/plate, did not induce his+ revertants, with or without metabolic activation, indicating its nonmutagenic nature . In the bone narrow micronucleus test using two doses in the range of therapeutic usage (10 and 20 mg/kg body weight), piperine itself was non-mutagenic . Like in somatic cells, piperine (10 and 50 mg/kg body weight) failed to induce mutations in male germ cells of mouse as assessed by using the sperm shape abnormality and dominant lethal tests . Piperine thus appears to be a non-genotoxic chemical. Mol Microbiol, 1996 Oct, 22(2), 367 - 78 Bacterial genetics by flow cytometry: rapid isolation of Salmonella typhimurium acid-inducible promoters by differential fluorescence induction; Valdivia RH et al.; The ability of Salmonella typhimurium to survive and replicate within murine macrophages is dependent on a low phagosomal pH . This requirement for an acidic vacuole suggests that low pH is an important environmental stimulus for the transcription of genes necessary for intracellular survival . To study the behaviour of acid-inducible genes in response to the phagosomal environment, we have applied a novel enrichment strategy, termed differential fluorescence induction (DFI), to screen an S . typhimurium library for promoters that are upregulated at pH 4.5 . DFI utilizes a fluorescence-enhanced green fluorescent protein (GFP) and a fluorescence-activated cell sorter (FACS) to perform genetic selection . In the presence of an inducing stimulus, such as low pH, a FACS is used to sort highly fluorescent bacterial clones bearing random promoters fused to the mutant GFP protein (GFPmut) . This population is then amplified at neutral pH and the least fluorescent population is sorted . Sequential sorts for fluorescent and non-fluorescent bacteria in the presence or absence of inducing conditions rapidly enriches for promoter fusions that are regulated by the inducing stimulus . We have identified eight acid-inducible promoters and quantified their expression in response to pH 4.5 and to the phagosome milieu . These acid-inducible promoters exhibited extensive homology to promoter regions of genes encoding for cell-surface-maintenance enzymes, stress proteins, and generalized efflux pumps . Only a subset of these promoters was induced in macrophages with kinetics and levels of expression that do not necessarily correlate with in vitro pH-shock induction . This suggests that while low pH is a relevant inducer of intracellular gene expression, additional stimuli in the macrophage can modulate the expression of acid-inducible genes. Infect Immun, 1996 Oct, 64(10), 4363 - 8 Invasion of murine intestinal M cells by Salmonella typhimurium inv mutants severely deficient for invasion of cultured cells; Clark MA et al.; We have examined the role of the Salmonella typhimurium inv locus in invasion of the murine intestine . Previous studies have demonstrated that M cells within the lymphoid-follicle-associated epithelia are the primary site of intestinal invasion by S . typhimurium . In this study, we show that mutants possessing defects in one of two inv genes, invA or invG, which render them severely deficient for invasion of polarized epithelial MDCK cells, retain their ability to actively invade mouse Peyer's patch M cells . The interaction of these mutants with M cells was associated with apical membrane remodelling resembling that induced by wild-type strains . These data demonstrate that Salmonella invasion in vivo can proceed via mechanisms other than those previously defined in cultured cells. Fundam Appl Toxicol, 1996 Oct, 33(2), 212 - 9 Bacterial and human cell mutagenicity and mouse lung tumorigenicity of the oxygenated polynuclear aromatic hydrocarbon phenalenone; Wang JS et al.; Phenalenone (perinaphthenone) is a major oxygenated polynuclear aromatic hydrocarbon (oxy-PAH) atmospheric pollutant formed from the combustion of fossil fuels . Mutagenicity of phenalenone was measured in quantitative forward mutation assays with Salmonella typhimurium TM677 and metabolically competent human B-lymphoblastoid cell lines (MCL-5 and h1A1v2 cells), and its tumorigenicity was also assessed in a newborn mouse assay . Phenalenone was mutagenic in Salmonella in the presence of rat liver postmitochondrial supernatant (PMS) at a minimum detectable mutagen concentration (MDMC) of 12 micrograms/ml, but was not mutagenic in the absence of PMS at concentrations up to 100 micrograms/ ml . Phenalenone was not significantly mutagenic in either human cell line after 28 hr treatment, although mutant fractions were increased by nearly fivefold in h1A1v2 cells (at the tk locus) exposed at 30 micrograms/ml . However, after 72 hr treatment, phenalenone was mutagenic at the hprt locus in h1A1v2 cells with an MDMC of 3 micrograms/ml . Phenalenone was also tumorigenic in male BLU:Ha mice with a lung tumor incidence of 33% 6 months after injection with 4.2 mg phenalenone, the highest dose tested . Lung tumor multiplicity in this treatment group was 0.5 tumor/mouse . No increase in lung tumors in female mice was observed . Indices of lung tumor incidence (ED50) and multiplicity (TM1.0) for male mice were 29.3 and 34.9 mumol, respectively . These data suggest that phenalenone does not contribute significantly to the mutagenicity or carcinogenicity of combustion emission extracts. Mutat Res, 1996 Oct 1, 370(3-4), 203 - 8 Mutagenicity of 24-hour duplicate of Japanese diet; Mano H et al.; In order to elucidate the genotoxicological characteristics of the Japanese diet, the mutagenicity of 24-h duplicate of the diet samples were investigated . The mutagenicity of blue rayon extract was examined in the Ames Salmonella/microsome assay . Thirty-two (91.4%) of 35 samples revealed mutagenicity toward Salmonella typhimurium TA98 in the presence of S9 mix . The mutagenic activities showed significant correlations with the consumption rates of broiled fish (r = 0.517, p = 0.0021) and broiled meat (r = 0.494, p = 0.0036) . In other test conditions, 6 (17.1%), 5 (14.3%) and 8 (22.9%) samples were mutagenic to Salmonella typhimurium TA98 without S9 mix, TA100 with S9 mix and TA100 without S9 mix, respectively . Findings in the present study suggest that high consumption of broiled fish and broiled meat are important as the source of mutagens/carcinogens in the Japanese diet . In the present study, however, biological inference of these findings could not be made in relation to the occurrence of cancers, especially of the gastric cancer, which is the most prevalent form of cancer in Japan. J Vet Med Sci, 1996 Oct, 58(10), 1021 - 3 Biochemical changes in fowl serum during infection with Salmonella typhimurium; Itoh N et al.; Two groups of White Leghorns were inoculated with Salmonella Typhimurium in the breast muscle . One group was injected with amikacin every 9 hr (8 times) from 24 to 96 hr after the bacterial inoculation and the other group was given no amikacin . In both groups, a significant increase in the levels of aspartate aminotransferase and creatine kinase, and a significant decrease in the levels of alkaline phosphatase, total cholesterol and glucose were found 96 hr after inoculation . There were, however, no significant differences in the blood chemical values between the amikacin-treated group and non-treated group . The results from the present study may provide basic data for further investigation of blood chemical values during Salmonella infection and amikacin therapy in fowls. Microb Pathog, 1996 Oct, 21(4), 249 - 63 Immunoprotection by monoclonal antibodies to the porins and lipopolysaccharide of Salmonella typhimurium; Singh SP et al.; Monoclonal antibodies (MAbs) were raised against the outer membrane (OM) antigens of Salmonella typhimurium . Enzyme-linked immunosorbent assays and Western immunoblots indicated that 10 MAbs in the panel were specific for surface epitopes, and 10 recognized buried epitopes of OmpC or OmpD porins; three MAbs reacted with smooth lipo-polysaccharide (LPS), two bound rough LPS, and the remaining three MAbs apparently reacted with a porin-LPS complex . We screened these MAbs and immune polyclonal sera in CAF1 (Ity) mice for their relative immunoprotective potential against a challenge with 10 to 500 LD50 of the virulent S . typhimurium LT-2 strain WB600, or against two LD50 of purified OM from this organism . Polyclonal sera that contained high titers of antibodies to porin monomers and trimers, and LPS, provided significant protection (33 to 100% survivors) . Antiporin MAbs, when administered individually, did not protect or prolong the survival of mice . A mixture of MAbs with specificity for the surface, but not buried epitopes of porins, prolonged the survival of mice against endotoxemia, but none provided significant protection against mouse typhoid . MAbs specific for smooth (but not rough) LPS on the other hand, conferred significant protection against endotoxemia and mouse typhoid . Finally, MAbs that presumably recognized epitopes present in porin-LPS complexes, were also protective against endotoxemia and mouse typhoid . These results support the role of antibodies to LPS O-chains, porin-LPS complexes, and to a lesser degree, native porins in acquired resistance to infection by S . typhimurium. Mol Microbiol, 1996 Oct, 22(1), 149 - 60 Virulence and vaccine potential of Salmonella typhimurium mutants deficient in the expression of the RpoS (sigma S) regulon; Coynault C et al.; The alternative sigma factor RpoS (sigma S) is required for Salmonella virulence in mice . We report the immunizing capacity of Salmonella typhimurium rpoS and rpoS aroA mutants to protect susceptible BALB/c mice against subsequent oral challenge with virulent S . typhimurium . When administered orally or intraperitoneally, rpoS derivatives of the mouse-virulent S . typhimurium strains, C52 and SL1344, were highly attenuated and were efficient single-dose live vaccines . rpoS aroA mutants were more attenuated than corresponding single aroA or rpoS mutants, as assessed after oral or intraperitoneal administration, but retained significant ability to protect mice against salmonellosis . Salmonella rpoS and rpoS aroA mutants therefore deserve serious consideration for rational vaccine design . Consistent with this, Salmonella typhi Ty2, a 'wild-type' strain used widely for the development of human live-vaccine candidates against typhoid fever, was shown to be defective for rpoS . In addition, our results demonstrate that rpoS not only controls the growth and persistence of S . typhimurium in deep lymphoid organs, but also plays a role during the initial stages of oral infection. Carcinogenesis, 1996 Oct, 17(10), 2275 - 7 Glutathione modulates the formation of 8-hydroxydeoxyguanosine in isolated DNA and mutagenicity in Salmonella typhimurium TA100 induced by mineral fibres; Howden PJ et al.; Treatment of isolated DNA with crocidolite and man-made vitreous fibre-21 (MMVF-21) significantly increased the concentration of 8-hydroxydeoxyguanosine (8-OHdG) in isolated DNA above background levels and co-treatment with glutathione (GSH) eliminated this effect . Crocidolite, MMVF-21 and chrysotile fibres increased the number of revertants in Salmonella typhimurium TA100 and GSH-deficient strains, TA100/NG-54 and TA100/NG-57, over background levels . This increase was small in TA100 but was greater in the GSH-deficient strains . When these bacterial strains were further depleted of GSH by co-culture with buthionine sulfoximine, all fibres tested caused a significant increase in the number of revertants over the parent strains . Pre-treatment with the GSH precursor N-acetyl-L-cysteine reduced the number of revertants to below that of the parent strain . Previous studies have shown a mechanistic role for iron-catalyzed production of oxygen radicals in the mutagenicity of fibres and this study suggests a protective role for GSH against such oxidative damage possibly by acting as a radical scavenger. Biophys J, 1996 Oct, 71(4), 2040 - 8 Interactions of phage P22 tails with their cellular receptor, Salmonella O-antigen polysaccharide; Baxa U et al.; Bacteriophage P22 binds to its cell surface receptor, the repetitive O-antigen structure in Salmonella lipopolysaccharide, by its six homotrimeric tailspikes . Receptor binding by soluble tailspikes and the receptor-inactivating endorhamnosidase activity of the tailspike protein were studied using octa- and dodecasaccharides comprising two and three O-antigen repeats of Salmonella enteritidis and Salmonella typhimurium lipopolysaccharides . Wild-type tailspike protein and three mutants (D392N, D395N, and E359Q) with defective endorhamnosidase activity were used . Oligosaccharide binding to all three subunits, measured by a tryptophan fluorescence quench or by fluorescence depolarization of a coumarin label attached to the reducing end of the dodecasaccharide, occurs independently . At 10 degrees C, the binding affinities of all four proteins to oligosaccharides from both bacterial strains are identical within experimental error, and the binding constants for octa- and dodecasaccharides are 1 x 10(6) M(-1) and 2 x 10(6) M(-1), proving that two O-antigen repeats are sufficient for lipopolysaccharide recognition by the tailspike . Equilibration with the oligosaccharides occurs rapidly, but the endorhamnosidase produces only one cleavage every 100 s at 10 degrees C or about 2 min(-1) at the bacterial growth temperature . Thus, movement of virions in the lipopolysaccharide layer before DNA injection may involve the release and rebinding of individual tailspikes rather than hydrolysis of the O-antigen. Proc Natl Acad Sci U S A, 1996 Oct 1, 93(20), 10584 - 8 Crystal structure of phage P22 tailspike protein complexed with Salmonella sp . O-antigen receptors; Steinbacher S et al.; The O-antigenic repeating units of lipopolysaccharides from Salmonella serogroups A, B, and D1 serve as receptors for the phage P22 tailspike protein, which also has receptor destroying endoglycosidase (endorhamnosidase) activity, integrating the functions of both hemagglutinin and neuraminidase in influenza virus . Crystal structures of the tailspike protein in complex with oligosaccharides, comprising two O-antigenic repeating units from Salmonella typhimurium, Salmonella enteritidis, and Salmonella typhi 253Ty were determined at 1.8 A resolution . The active-site topology with Asp-392, Asp-395, and Glu-359 as catalytic residues was identified . Kinetics of binding and cleavage suggest a role of the receptor destroying endorhamnosidase activity primarily for detachment of newly assembled phages. J Bacteriol, 1996 Oct, 178(20), 5904 - 9 Molecular characterization of the oafA locus responsible for acetylation of Salmonella typhimurium O-antigen: oafA is a member of a family of integral membrane trans-acylases; Slauch JM et al.; Lipopolysaccharide (LPS) coats the surface of gram-negative bacteria and serves to protect the cell from its environment . The O-antigen is the outermost part of LPS and is highly variable among gram-negative bacteria . Strains of Salmonella are partly distinguished by serotypic differences in their O-antigen . In Salmonella typhimurium, the O-antigen is acetylated, conferring the 05 serotype . We have previously provided evidence that this modification significantly alters the structure of the O-antigen and creates or destroys a series of conformational epitopes . Here we report the detailed mapping, cloning, and DNA sequence of the oafA gene . The locus contains one open reading frame that is predicted to encode an inner membrane protein, consistent with its role in modification of the O-antigen subunit . The OafA protein shows homology to proteins in a number of prokaryotic and one eukaryotic species, and this defines a family of membrane proteins involved in the acylation of exported carbohydrate moieties . In many of these instances, acylation defines serotype or host range and thus has a profound effect on microbe-host interaction. J Bacteriol, 1996 Oct, 178(19), 5683 - 91 The role of fur in the acid tolerance response of Salmonella typhimurium is physiologically and genetically separable from its role in iron acquisition; Hall HK et al.; The response of Salmonella typhimurium to low pH includes a low-pH protection system called the acid tolerance response (ATR) . The iron-regulatory protein Fur has been implicated in the ATR since fur mutants are acid sensitive and cause altered expression of several acid shock proteins (J . W . Foster, J . Bacteriol . 173:6896-6902, 1991) . We have determined that the acid-sensitive phenotype of fur mutations is indeed due to a defect in Fur that can be complemented by a fur(+)-containing plasmid . However, changes in cellular iron status alone did not trigger the ATR . Cells clearly required exposure to low pH in order to induce acid tolerance . The role of Fur in acid tolerance was found to extend beyond regulating iron acquisition . A mutation in fur converting histidine 90 to an arginine (H90R) eliminated Fur-mediated iron regulation of enterochelin production and deregulated an iroA-lacZ fusion but had no effect on acid tolerance . The H90R iron-blind Fur protein also mediated acid shock induction of several Fur-dependent acid shock proteins and acid control of the hyd locus . In addition, a Fur superrepressor that constitutively repressed iron-regulated genes mediated normal Fur-dependent acid tolerance and pH-controlled gene expression . The results indicate the acid-sensing and iron-sensing mechanisms of Fur are separable by mutation and reinforce the concept of Fur as a major global regulator in the cell. J Bacteriol, 1996 Oct, 178(19), 5676 - 82 Mutations in apbC (mrp) prevent function of the alternative pyrimidine biosynthetic pathway in Salmonella typhimurium; Petersen L et al.; The alternative pyrimidine biosynthetic (APB) pathway can synthesize the 4-amino-5-hydroxymethyl-2-methyl pyrimidine (HMP) moiety of thiamine in Salmonella typhimurium independently of de novo purine biosynthesis . When mutants defective in function of the APB pathway were isolated, the predominant class (40%) were defective in a single locus we have designated apbC . Mutations in apbC block function of the APB pathway since they prevent growth of a purF mutant in the absence of thiamine . Lesions in apbC also cause a thiamine auxotrophy in strains proficient in purine biosynthesis when fructose is provided as the sole carbon and energy source . Results presented here are consistent with ApbC being involved in the conversion of aminoimidazole ribonucleotide to HMP, and we suggest that ApbC performs a redundant step in thiamine synthesis . Sequence analysis demonstrated that apbC mutations were alleles of mrp, a locus previously reported in Escherichia coli as a metG-related protein . We propose that this locus in S . typhimurium be designated apbC to reflect its involvement in thiamine synthesis. Clin Immunol Immunopathol, 1996 Oct, 81(1), 55 - 61 Suppressive effect of transforming growth factor beta1 on the recurrence of experimental melanin protein-induced uveitis: upregulation of ocular interleukin-10; Li Q et al.; Uveitis is induced in Lewis rats by immunization with bovine melanin protein (BMP) derived from the uvea and retinal pigment epithelium . Recurrence of this experimental melanin protein-induced uveitis (EMIU) develops after footpad injection of a minimal amount of Salmonella typhimurium endotoxin (LPS) following the remission of EMIU . To investigate the effect of transforming growth factor beta1 (TGFbeta1) on the recurrence of EMIU, 5 micrograms LPS booster was given to Lewis rats by footpad injection on Day 45 after BMP immunization . Daily TGFbeta1 or phosphate-buffered saline was administered either from Day 0 to 7 (group 1) or from Day 7 to 13 (group 2) after LPS booster . Delayed-type hypersensitivity (DTH) ear test was conducted on Day 12 after LPS booster and eye and blood were collected on Day 14 . The incidence and severity of recurrent uveitis markedly decreased in both groups of TGFbeta1-treated rats . A lower level of serum BMP antibody was also observed by agglutination in these groups . There was no statistical difference in DTH responses between the treated and control groups . Ocular cytokine mRNA of group 1 and controls was analyzed by RT-PCR . Interleukin (IL)-2 and interferon-gamma were not detectable . IL-4 was identified at a similar level in both groups . A higher level of IL-10 was observed in group 1 rats . We conclude that TGFbeta1 suppresses recurrent EMIU, probably through upregulation of IL-10. Mutat Res, 1996 Sep 26, 361(1), 41 - 8 Bacterial photomutagenicity testing: distinction between direct, enzyme-mediated and light-induced events; Utesch D et al.; A bacterial photomutagenicity test system has been established according to a predetermined protocol using a light source emitting multiple wave lengths, including UV-A and UV-B, and the tester strains used for standard bacterial mutagenicity testing . 8-Methoxypsoralen (8-MOP) was used as a photomutagenic positive control showing no mutagenicity in the absence of light and borderline (Salmonella typhimurium TA1537) or clear (Salmonella typhimurium TA102 and Escherichia coli WP2) mutagenic effects in the presence of light . Using the same experimental conditions, the UV filters p-aminobenzoic acid (PABA), octyl dimethyl PABA (Eusolex 6007), and 4-methylbenzylidene camphor (Eusolex 6300) were non-mutagenic (in the absence of light) and non-photomutagenic (in the presence of light) . Dihydroxyacetone (DHA), used as an active ingredient in self-tanning lotions, slightly increased the number of revertants in Salmonella typhimurium TA100 and TA102 in the absence of light . However, the relevance of these effects is equivocal, since they occurred at very high, cytotoxic concentrations (5000 micrograms/plate) . Furthermore, these increases were not potentiated by light, thus demonstrating the non-photomutagenicity of DHA . In contrast, 7,12-dimethylbenz{a}anthracene (DMBA), which is non-mutagenic per se and is activated by external metabolizing systems (e.g., S9-mix) in the absence of light, was clearly mutagenic in Salmonella typhimurium TA98 and TA1537 in the presence of light (and the absence of S9-mix) . Although the photomutagenic potency of DMBA, on a molar basis, was certainly lower than that of 8-MOP, the absolute mutagenic effects of DMBA in the respective bacterial strains were in a similar range under either S9-mix or photoactivation conditions . The strain specificity of the mutagenic effects were, however, different for either enzyme- or light-mediated mutagenicity . This indicates that different reactive intermediates are responsible for the mutagenicity in the tests using the two different activation systems . These results further suggest to use DMBA as a positive photomutagenic control compound alternatively to 8-MOP, since the latter is non- or only weakly photomutagenic in Salmonella typhimurium TA98 and TA1537 . Furthermore, the usefulness and application of this photomutagenicity test system could be demonstrated for the testing of different photoabsorbing chemicals and cosmetic ingredients. Proc Natl Acad Sci U S A, 1996 Sep 17, 93(19), 10303 - 8 Highly plastic chromosomal organization in Salmonella typhi; Liu SL et al.; Gene order in the chromosomes of Escherichia coli K-12 and Salmonella typhimurium LT2, and in many other species of Salmonella, is strongly conserved, even though the genera diverged about 160 million years ago . However, partial digestion of chromosomal DNA of Salmonella typhi, the causal organism of typhoid fever, with the endonuclease I-CeuI followed by separation of the DNA fragments by pulsed-field gel electrophoresis showed that the chromosomes of independent wild-type isolates of S . typhi are rearranged due to homologous recombination between the seven rrn genes that code for ribosomal RNA . The order of genes within the I-CeuI fragments is largely conserved, but the order of the fragments on the chromosome is rearranged . Twenty-one different orders of the I-CeuI fragments were detected among the 127 wild-type strains we examined . Duplications and deletions were not found, but transpositions and inversions were common . Transpositions of I-CeuI fragments into sites that do not change their distance from the origin of replication (oriC) are frequently detected among the wild-type strains, but transpositions that move the fragments much further from oriC were rare . This supports the gene dosage hypothesis that genes at different distances from oriC have different gene dosages and, hence, different gene expression, and that during evolution genes become adapted to their specific location; thus, cells with changes in gene location due to transpositions may be less fit . Therefore, gene dosage may be one of the forces that conserves gene order, although its effects seem less strong in S . typhi than in other enteric bacteria . However, both the gene dosage and the genomic balance hypotheses, the latter of which states that the origin (oriC) and terminus (TER) of replication must be separated by 180 degrees C, need further investigation. Biochim Biophys Acta, 1996 Sep 11, 1308(3), 189 - 92 Cloning and characterization of the tyrB gene from Salmonella typhimurium; Nakai Y et al.; We found a gene homologous to tyrB, which encodes aromatic amino acid aminotransferase (ArAT, EC2.6.1.57) in Escherichia coli, in the genome of Salmonella typhimurium IFO 13245 . The S . typhimurium tyrB product consists of 397 amino acid residues . The amino acid sequence shows 87.9% identity with that of E . coli ArAT, but shows lower identity (42.3%) with that of E . coli aspartate aminotransferase (AspAT, EC2.6.1.1) . When the S . typhimurium tyrB gene was expressed in an E . coli mutant whose intrinsic tyrB gene had been inactivated, the activity of transaminating tyrosine and phenylalanine could be recovered, indicating that the S . typhimurium tyrB gene product possesses transamination activities similar to those of the E . coli ArAT . Elucidation of the molecular features of a new ArAT may be helpful for structural and functional analyses of ArAT and AspAT with regard to the different but overlapping substrate specificity of the two enzymes. J Immunol Methods, 1996 Sep 9, 195(1-2), 15 - 25 Enzyme-linked immunomagnetic electrochemical detection of Salmonella typhimurium; Gehring AG et al.; There is a need for rapid methods to detect pathogenic bacteria in food products as alternatives to the current laborious and time-consuming culture procedures . We report a microbial detection technique that combines the selectivity of antibody-coated superparamagnetic beads with the rapidity and sensitivity of electrochemical detection in a format termed enzyme-linked immunomagnetic electrochemistry . In it, Salmonella typhimurium were sandwiched between antibody-coated magnetic beads and an enzyme-conjugated antibody . With the aid of a magnet, the beads (with or without bound bacteria) were localized onto the surface of disposable graphite ink electrodes in a multi-well plate format . Enzyme substrate was added and conversion of substrate to an electroactive product was measured using electrochemical detection . The electrochemical response was directly proportional to the number of captured bacteria . Using this technique, a minimum detectable level of 8 x 10(3) cells/ml of Salmonella typhimurium in buffer was achieved in ca . 80 min. Proc Natl Acad Sci U S A, 1996 Sep 3, 93(18), 9833 - 8 Salmonella typhimurium invasion induces apoptosis in infected macrophages; Monack DM et al.; Invasive Salmonella typhimurium induces dramatic cytoskeletal changes on the membrane surface of mammalian epithelial cells and RAW264.7 macrophages as part of its entry mechanism . Noninvasive S . typhimurium strains are unable to induce this membrane ruffling . Invasive S . typhimurium strains invade RAW264.7 macrophages in 2 h with 7- to 10-fold higher levels than noninvasive strains . Invasive S . typhimurium and Salmonella typhi, independent of their ability to replicate intracellularly, are cytotoxic to RAW264.7 macrophages and, to a greater degree, to murine bone marrow-derived macrophages . Here, we show that the macrophage cytotoxicity mediated by invasive Salmonella is apoptosis, as shown by nuclear morphology, cytoplasmic vacuolization, and host cell DNA fragmentation . S . typhimurium that enter cells causing ruffles but are mutant for subsequent intracellular replication also initiate host cell apoptosis . Mutant S . typhimurium that are incapable of inducing host cell membrane ruffling fail to induce apoptosis . The activation state of the macrophage plays a significant role in the response of macrophages to Salmonella invasion, perhaps indicating that the signal or receptor for initiating programmed cell death is upregulated in activated macrophages . The ability of Salmonella to promote apoptosis may be important for the initiation of infection, bacterial survival, and escape of the host immune response. Biochemistry, 1996 Sep 3, 35(35), 11260 - 7 Mutation of serine-46 to aspartate in the histidine-containing protein of Escherichia coli mimics the inactivation by phosphorylation of serine-46 in HPrs from gram-positive bacteria; Napper S et al.; Histidine-containing protein (HPr) is a phosphocarrier protein of the bacterial phosphoenolpyruvate:sugar phosphotransferase system . HPr is phosphorylated at the active site residue, His15, by phosphoenolpyruvate-dependent enzyme I in the first enzyme reaction in the process of phosphoryl transfer to sugar . In many Gram-positive bacterial species HPr may also be phosphorylated at Ser46 by an ATP-dependent protein kinase but not in the Gram-negative Escherichia coli and Salmonella typhimurium . One effect of the phosphorylation at Ser46 is to make HPr a poor acceptor for phosphorylation at His15 . In Bacillus subtilis HPr, the mutation Ser46Asp mimics the effects of phosphorylation . A series of mutations were made at Ser46 in E . coli HPr: Ala, Arg, Asn, Asp, Glu, and Gly . The two acidic replacements mimic the effects of phosphorylation of Ser46 in HPrs from Gram-positive bacteria . In particular, when mutated to Asp46, the His 15 phosphoacceptor activity (enzyme I Km/Kcat) decreases by about 2000-fold (enzyme I Km, 4 mM HPr; Kcat, approximately 30%) . The alanine and glycine mutations had near-wild-type properties, and the asparagine and arginine mutations yielded small changes to the Km values . The crystallographic tertiary structure of Ser46Asp HPr has been determined at 1.5 A resolution, and several changes have been observed which appear to be the effect of the mutation . There is a tightening of helix B, which is demonstrated by a consistent shortening of hydrogen bond lengths throughout the helix as compared to the wild-type structure . There is a repositioning of the Gly54 residue to adopt a 3(10) helical pattern which is not present in the wild-type HPr . In addition, the higher resolution of the mutant structure allows for a more definitive placement of the carbonyl of Pro11 . The consequence of this change is that there is no torsion angle strain at residue 16 . This result suggests that there is no active site torsion angle strain in wild-type E . coli HPr . The lack of substantial change at the active center of E . coli HPr Ser46Asp HPr suggests that the effect of the Ser46 phosphorylation in HPrs from Gram-positive bacteria is due to an electrostatic interference with enzyme I binding. Zh Mikrobiol Epidemiol Immunobiol, 1996 Sep-Oct, (5), 76 - 80 {The evaluation of different agglutination and adhesion tests with erythrocytic reagents in determining antibodies to the O and H antigens of Salmonella typhimurium in comparison with immunoenzyme analysis (IEA)}; Karal'nik BV et al.; The comparison of the effectiveness of EIA with that of a number of agglutination and adhesion tests with erythrocyte diagnostica in the determination of antibodies to different S.typhimurium antigens demonstrated higher sensitivity of EIA . The relative specificity of the determination of O- and H-antibodies in EIA and in agglutination and adhesion tests depended on the isotype of antibodies to be determined and the specificity of sensitins used in the production of immunoreagents. East Afr Med J, 1996 Sep, 73(9), 575 - 8 Prevalence of human immunodeficiency virus infection: its impact on the diagnostic yields in exudative pleural effusions at the Kenyatta National Hospital, Nairobi; Owino EA et al.; This was a descriptive cross-sectional study carried out at Kenyatta National Hospital (KNH), Nairobi, among consecutively admitted adult patients with exudative pleural effusions over a one year period . The aim of the study was to determine the prevalence of human immunodeficiency virus (HIV) infection in these patients and to compare the diagnostic yields from the pleural fluid and pleural biopsy between the HIV seropositive and HIV seronegative patients . Sixty six patients were studied, with a mean age of 33.8 (+/- SD = 15.6) years and a male to female ratio of 1.6:1 . Overall, 27 patients(40.9%) were found to be HIV seropositive . The commonest cause of exudative pleural effusions, overall, was tuberculosis (78.8%) followed by neoplasms (7.6%) . Comparing the aetiology of exudative pleural effusion in HIV seropositive and HIV seronegative patients, tuberculosis was still the commonest cause accounting for 42.3% and 57.7% of the cases in each of the groups respectively . Conversely, 42.3% of patients with tuberculous pleural effusions were HIV seropositive . There was no significant difference in yields from pleural fluid, pleural biopsy culture and histology in the diagnosis of tuberculosis in the two patient groups . The only two patients with empyema were HIV seropositive and the bacterial isolates were Salmonella typhimurium and Pseudomonas aeruginosa . Kaposi's sarcoma was the cause of exudative pleural effusion in the one HIV seropositive patient with a malignant effusion . The only patient with a parapneumonic effusion was HIV seronegative . No fungi were isolatedPIP: 66 adult patients of mean age 33.8 years with exudative pleural effusions were studied to determine the prevalence of HIV infection and compare the diagnostic yields from the pleural fluid and pleural biopsy between the HIV-seropositive and HIV-seronegative patients . The patients were consecutively admitted to Kenyatta National Hospital (KNH) over a 1-year period and of male:female ratio 1.6:1 . 27 patients were found to be HIV seropositive . Tuberculosis (TB) and neoplasms were the most common causes of exudative pleural effusions, responsible for 78.8% and 7.6% of cases, respectively . Comparing the etiology of exudative pleural effusion in HIV-seropositive and HIV-seronegative patients, TB remained the most common cause, accounting for 42.3% and 57.7% of cases in each of the groups, respectively . 42.3% of the patients with TB pleural effusions were HIV seropositive . No significant difference was identified in the yields from pleural fluid, pleural biopsy culture, and histology in the diagnosis of TB in the 2 patient groups . The only 2 patients with empyema were HIV seropositive and the bacterial isolates were Salmonella typhimurium and Pseudomonas aeruginosa . Kaposi's sarcoma was the cause of exudative pleural effusion in the 1 HIV-seropositive patient with a malignant effusion . The only patient with a parapneumonic effusion was HIV seronegative . No fungi were isolated . Mutagenesis, 1996 Sep, 11(5), 519 - 23 Role of oxidative DNA damage in hydroxychavicol-induced genotoxicity; Lee-Chen SF et al.; Chewing betel quid has been linked to the development of oral cancer . In Taiwan, fresh Piper betle inflorescence is uniquely added to betel quid, and hydroxychavicol is the major phenolic components of P.betle inflorescence . In this study, we tested the mutagenic potential of hydroxychavicol in Salmonella typhimurium TA97, TA98, TA100 and TA102 with and without Aroclor-1254 induced S9 fraction . The results showed that hydroxychavicol was positive in S.typhimurium TA102 without metabolic activation . This increase in revertants was partially inhibited by catalase and superoxide dismutase . In Chinese hamster ovary (CHO-K1) cells, hydroxychavicol induced chromosome aberrations in a dose-dependent manner (10-50 microM) and the majority were chromosome-type aberrations . Hydroxychavicol also significantly increased the frequency of micronuclei in CHO-K1 cells up to 3-fold at a concentration of 40 microM . In addition, hydroxychavicol dose-dependently (0.1-20 microM) induced copper-dependent strand breaks in plasmid DNA . We further tested the oxidative DNA damage potential of hydroxychavicol by measuring 8-hydroxydeoxyguanosine (8-OH-dG) formation in CHO-K1 cells following an 18-h incubation and found that hydroxychavicol (6.25-100 microM) induced 8-OH-dG levels dose-dependently . The increase of 8-OH-dG formation was positively correlated (r = 0.79) with the hydroxychavicol-induced cytotoxicity . In conclusion, hydroxychavicol may exert its genotoxic potential through oxidative DNA damage. Mutagenesis, 1996 Sep, 11(5), 497 - 504 The photomutagenicity of fluoroquinolones in tests for gene mutation, chromosomal aberration, gene conversion and DNA breakage (Comet assay); Chetelat AA et al.; The ability of fluoroquinolones to cause light-induced adverse effects has been established in experimental studies and clinical observations . The formation of active oxygen species appears to be responsible for this activity . Photomutagenicity tests with bacterial, lower eukaryotic and mammalian cells were performed with three fluoroquinolones (Fleroxacin, Ciprofloxacin and Lomefloxacin) . After concomitant irradiation with simulated solar light (with a reduced UVB component), weak increases in the number of revertants were observed in Salmonella typhimurium TA104 and TA100 . No photomutagenic activity was detected in Saccharomyces cerevisiae D7 . In the chromosomal aberration (CA) test with Chinese hamster V79 cells the number of aberrant metaphases was markedly increased . In the Comet assay with mouse lymphoma cells, evidence of extensive DNA breakage was obtained . All three compounds showed similar potencies in the Comet and Ames assays while there was a clear gradation of potencies in the CA assay (Lomefloxacin > Fleroxacin > Ciprofloxacin), which conformed with reports on the relative potencies regarding phototoxicity . The oxygen radical scavengers catalase, superoxide dismutase and N, N'-dimethylurea modulated the photoclastogenicity and phototoxicity but had no influence on the effects in the Comet and Ames tests . It thus appears that different kinds of mechanism are responsible for toxicity and clastogenicity on the one side and DNA breakage and gene mutation on the other side . Pre-irradiation of the test articles did not lead to enhanced genotoxicity, indicating the involvement of very short lived genotoxic agents . The results endorse the advice to avoid excessive light exposure during antibiotic therapy with fluoroquinolones. Cancer Immunol Immunother, 1996 Sep, 43(1), 44 - 8 Induction of an antibody response in mice against human papillomavirus (HPV) type 16 after immunization with HPV recombinant Salmonella strains; Krul MR et al.; Human papillomaviruses (HPV) are present in approximately 95% of all cervical carcinomas and the HPV E6 and E7 genes are continuously expressed in these lesions . There is also circumstantial evidence that often natural immunity against HPV is generated and that this is of influence on HPV-induced lesions . Stimulation of the immune system by proper presentation of relevant HPV antigens might, therefore, lead to a prophylactic or therapeutic immunological intervention for HPV-induced lesions . For this purpose we have expressed the E6 and E7 protein of HPV 16 in an attenuated strain of Salmonella typhimurium (SL3261, aroA mutation), which has been used extensively as a live vector . Live recombinant Salmonella vaccines have the ability to elicit humoral, secretory and cell-mediated immune responses, including cytotoxic T cells, against the heterologous antigens they express . This report describes the construction of recombinant Salmonella strains expressing the HPV 16 E6 and E7 proteins, and the induction of an HPV-16-specific immune response in mice after immunization with these live vectors. Crit Rev Toxicol, 1996 Sep, 26(5), 551 - 83 New applications of bacterial systems to problems in toxicology; Guengerich FP et al.; Bacterial systems have long been of use in toxicology . In addition to providing general models of enzymes and paradigms for biochemistry and molecular biology, they have been adapted to practical genotoxicity assays . More recently, bacteria also have been used in the production of mammalian enzymes of relevance to toxicology . Escherichia coli has been used to express cytochrome P450, NADPH-cytochrome P450 reductase, flavin-containing monooxygenase, glutathione S-transferase, quinone reductase, sulfotransferase, N-acetyltransferase, UDP-glucuronosyl transferase, and epoxide hydrolase enzymes from humans and experimental animals . The expressed enzymes have been utilized in a variety of settings, including coupling with bacterial genotoxicity assays . Another approach has involved expression of mammalian enzymes directly in bacteria for use in genotoxicity systems . Particularly with Salmonella typhimurium . Applications include both the reversion mutagenesis assay and a system using a chimera with an SOS-response indicator and a reporter. J Appl Physiol, 1996 Sep, 81(3), 1316 - 22 Endotoxin alters hypoxic pulmonary vasoconstriction in isolated rat lungs; Frank DU et al.; Hypoxic pulmonary vasoconstriction (HPV) is an important mechanism for maintaining oxygenation, which may be altered by endotoxin . We determined that acute endotoxemia alters the HPV response secondary to changes in endothelium-derived vasoactive products . Rats were treated with Salmonella typhimurium lipopolysaccharide (LPS; 15 mg/kg i.p.) either 1 to 6 h before lung isolation and compared with control rats (no LPS) . Additional 6-h LPS-treated and control rats were pretreated with either indomethacin (15 mg/kg i.p.), a cyclooxygenase inhibitor, or bosentan (10 mg/kg po), a nonselective endothelin-receptor antagonist . The rats lungs were isolated and challenged with 3% O2 for 10 min to elicit HPV responses before and after nitric oxide (NO) synthase inhibition with N omega-nitro-L-arginine methyl ester (L-NAME; 100 microM) . LPS (6 h) significantly increased the peak HPV responses by 108% . L-NAME had no significant effect in LPS-treated lungs but increased the peak HPV response in control lungs to levels equal to LPS-treated lungs . Bosentan increased the peak HPV response in all lungs, and indomethacin increased the peak HPV in LPS-treated lungs . The HPV response was sustained in control lungs at 10 min and in additional 20-min studies . In contrast, in LPS-treated lungs the HPV response faded after 10 min to levels equal to control, and in 20-min studies it faded by 82% to levels significantly less than in control lungs . The 10-min fade in LPS-treated lungs was attenuated by indomethacin (51%) and bosentan (80%) but not by L-NAME . In conclusion, acute endotoxemia with LPS increased the peak HPV response, but this effect was not sustained and by 20 min was nearly abolished . Inhibition of endogenous NO by LPS may explain the increased peak HPV response, but NO is not involved in the fade . The fade is at least partially due to increased vasodilating cyclooxygenase products and endothelins. J Antimicrob Chemother, 1996 Sep, 38(3), 425 - 34 Multi-drug resistant non-typhi salmonellae in Kenya; Kariuki S et al.; Two methods of plasmid characterization, restriction digest patterns and incompatibility grouping, were used to study self-transmissible multi-drug resistance among non-typhi salmonellae (NTS) . Resistance to ampicillin and other commonly applied beta-lactams was evaluated by iso-electric focusing and disc inactivation . Of the NTS isolated from blood, 75% were Salmonella typhimurium but those included several different phage types . Over 47% of isolates were resistant to three or more of the readily available drugs including ampicillin, cefuroxime, chloramphenicol, co-trimoxazole, streptomycin and tetracycline . Self-transferable resistance plasmids (c . 100 kb) were essentially of incompatibility group incFIIA, but their restriction fragment patterns revealed a diversity in relatedness . More than half of parent strains and their transconjugants produced beta-lactamases which co-electrophoresed with TEM-1 and OXA-1 . This study has observed a disturbingly high prevalence of transmissible multi-drug resistance among NTS which are an important cause of morbidity in HIV-1 seropositive individuals. Int J Food Sci Nutr, 1996 Sep, 47(5), 391 - 8 Splenic and intestinal lymphocyte proliferation response in mice fed milk or yogurt and challenged with Salmonella typhimurium; Puri P et al.; Two groups of 4-5 week old DBA/2J Nii mice were put on either a yogurt-based (n = 33) or a milk-based (n = 32) diet for a period of 4 weeks . At the end of the feeding trial one sub group of mice each from the two dietary groups was sacrificed for assessment of immune response . The remaining mice were challenged intragastrically with 2 x 10(10) live Salmonella typhimurium organisms and continued on their respective diets for 8 days after which they were also sacrificed . The immune response was measured by tritiated thymidine uptake by splenic or intestinal lymphocytes in response to the mitogens concanavalin A (Con A), Phytohaemaggutinin (PHA), and Lipopolysaccharide from Escherichia coli (LPS) . Serum Immunoglobulin A levels were also estimated . Feed efficiency, measured as weight gain per unit energy intake, was significantly higher for the yogurt diet than for the milk diet . The mitogenic response of splenic and intestinal lymphocytes in the two groups of unchallenged mice was not different . In the Salmonella-challenged mice the stimulation index (SI) of splenic lymphocytes from yogurt-fed mice (mean +/- SD) was significantly higher (P = 0.001) in response to Con A (24.71 +/- 3.40) than that of milk-fed mice (15.85 +/- 2.09) . Further, in these mice the SI of intestinal lymphocytes from yogurt-fed mice was higher than that of milk-fed mice in response to Con A (7.35 +/- 0.61 vs 5.65 +/- 0.78, P = 0.016) and LPS (9.04 +/- 0.93 vs 6.15 +/- 1.32, P = 0.016) . Serum IgA levels in Salmonella-challenged mice were significantly higher 8 days after the challenge in the yogurt-fed group than in the milk-fed group (P < 0.001) . The experiments indicate an improvement in local gastrointestinal as well as systemic immunity on a yogurt diet as compared to a milk diet. Mol Microbiol, 1996 Sep, 21(5), 1101 - 15 Salmonella spp . are cytotoxic for cultured macrophages; Chen LM et al.; We have shown by a variety of microscopical and biochemical techniques that Salmonella spp . are cytotoxic for cultured J774A.1 and bone marrow-derived murine macrophages . The cytotoxicity is initially manifested by inhibition of membrane ruffling and macropinocytosis in infected macrophages, and is followed by cell death . Macrophages killed by Salmonella spp . exhibited features of apoptosis such as condensation and fragmentation of chromatin, membrane blebbing, and the presence of cytoplasmic nucleosomes and apoptotic bodies . Cytotoxicity does not require bacterial internalization as cytochalasin D, a drug that prevents bacterial uptake, did not prevent Salmonella-induced macrophage cell death . However, the cytotoxic effects are strictly dependent upon the expression of the invasion-associated Type III protein-secretion system encoded at centisome 63 of the Salmonella chromosome . Wild-type Salmonella typhimurium grown under conditions that do not allow optical expression of this system or strains of Salmonella carrying mutations in genes that encode components of this protein-secretion system were devoid of macrophage cytotoxicity . In addition, mutations in invJ, spaO, sipB, sipC and sipD, which encode proteins that are secreted via this secretion apparatus and are required for bacterial entry into non-phagocytic cells, also abolished the toxicity . In contrast, mutations in sipA and sptP, which encode secreted proteins that are not required for bacterial invasion, had no effect on macrophage cytotoxicity . These results indicate a close correlation between the mechanisms of bacterial internalization into non-phagocytic cells and those that lead to macrophage cytotoxicity . Host-adapted serotypes of Salmonella such as S . typhi, S . gallinarum and S . dublin were also toxic for murine macrophages, indicating that this virulence property is probably present in most Salmonella spp . and is not associated with the mechanisms responsible for host range. Genetics, 1996 Sep, 144(1), 15 - 26 DNA adenine methylase mutants of Salmonella typhimurium and a novel dam-regulated locus; Torreblanca J et al.; Mutants of Salmonella typhimurium lacking DNA adenine methylase were isolated; they include insertion and deletion alleles . The dam locus maps at 75 min between cysG and aroB, similar to the Escherichia coli dam gene . Dam- mutants of S . typhimurium resemble those of E coli in the following phenotypes: (1) increased spontaneous mutations, (2) moderate SOS induction, (3) enhancement of duplication segregation, (4) inviability of dam recA and dam recB mutants, and (5) suppression of the inviability of the dam recA and dam recB combinations by mutations that eliminate mismatch repair . However, differences between S . typhimurium and E . coli dam mutants are also found: (1) S . typhimurium dam mutants do not show increased UV sensitivity, suggesting that methyl-directed mismatch repair does not participate in the repair of UV-induced DNA damage in Salmonella . (2) S . typhimurium dam recJ mutants are viable, suggesting that the Salmonella RecJ function does not participate in the repair of DNA strand breaks formed in the absence of Dam methylation . We also describe a genetic screen for detecting novel genes regulated by Dam methylation and a locus repressed by Dam methylation in the S . typhimurium virulence (or "cryptic") plasmid. Pediatr Res, 1996 Sep, 40(3), 415 - 21 Escherichia coli transcytosis in a Caco-2 cell model: implications in neonatal necrotizing enterocolitis; Panigrahi P et al.; Necrotizing enterocolitis (NEC) is a serious gastrointestinal disorder of preterm infants . Other than an association with prematurity and gastrointestinal feeding, no single factor or mechanism has been consistently linked to this disease . We have previously demonstrated that Escherichia coli isolates obtained from the stool of infants with NEC caused NEC-like injury in a weanling rabbit ileal loop model; this injury, in turn, could be blocked by coinfection with selected Gram(+) bacteria (Enterococcus faecium) isolated from asymptomatic controls . Using Caco-2 cells in a trans-well system, we now demonstrate that the same E . coli isolates can cross epithelial cell monolayers in the absence of ultrastructural change or damage . These results with E . coli contrast with those seen with Salmonella typhimurium, which passed through the monolayer at a higher rate and were associated with striking ultrastructural damage . Transcytosis of E . coli was reduced 3-5-fold in the presence of E . faecium previously shown to block NEC-like injury in the loop model . There was a mild increase in the rate of E . coli transcytosis when studies were conducted with younger, undifferentiated cells; these immature cells had no brush border, had decreased production of brush border-specific enzymes, but retained well defined tight junctions, as demonstrated by transepithelial electrical resistance and electron microscopy . A further reduction/ complete blockage of E . coli transcytosis was observed when E . faecium was used as the coinfectant in studies with these undifferentiated cells . We hypothesize that the ability of E . coli to cross epithelial cell layer is a critical initial step in the cascade of events which lead ultimately to NEC; blockage or reduction in E . coli transcytosis in the presence of certain Gram(+) organisms may play a significant role in prevention of NEC. Carcinogenesis, 1996 Sep, 17(9), 2009 - 12 Synthesis and mutagenicity of some cyclopenta{c}phenanthrenes and indeno{c}phenanthrenes; Marrocchi A et al.; An efficient two-step synthesis of 8(H)-9,10,11,12-tetra-hydrodicyclopenta{a,c}phenanthren-7-one, based on the high pressure Diels-Alder cycloaddition of 4-acetoxy-2-cyclopenten-1-one with 1-(1-naphthyl)cyclopentene and a subsequent dehydrogenation-aromatization reaction, is reported . Further, the synthesis of two cyclopenta{c}-phenanthrenes and indeno{c}phenanthrenes is described . Structural analysis of the new products by 1H and 13C NMR spectroscopy is presented . The mutagenic activity of the compounds in Salmonella typhimurium was estimated by Ames' test . Three compounds were shown to be mutagenic for the strain TA 100 . The mutagenic activities exhibited by cyclopenta{c}phenanthrenes are compared with those shown by the related cyclopenta{a}phenanthrenes and then discussed with respect to the effect of the cyclopentane ring facing the bay region . Indeno{c}phenanthrenes are mostly inactive . The effect of benzoannulation on the mutagenic activities of cyclopenta{c}phenanthrenes is discussed. Plant J, 1996 Sep, 10(3), 479 - 89 A transposon insertion in the Arabidopsis SSR16 gene causes an embryo-defective lethal mutation; Tsugeki R et al.; The SSR16 gene of Arabidopsis has been identified as a gene encoding a ribosomal protein S16 homolog through analysis of a transposon insertion mutation . The insertion mutation is lethal, arresting embryonic development at approximately the transition from the globular to the heart stage of embryonic development . Co-segregation of the mutant phenotype with the transposon-borne drug-resistance marker and loss of the inserted transposon concomitant with phenotypic reversion provided evidence that the transposon had caused the mutation . Sequences flanking the insertion site were amplified from DNA of viable heterozygotes by thermal asymmetric interlaced (TAIL) PCR . The amplified fragment flanking the 3' end of the inserted element was sequenced and found to be identical to an Arabidopsis expressed sequence tag (EST) . The EST, in turn, contained a coding sequence homologous to the ribosomal protein S16 (RPS16) of bacteria such as Escherichia coli, Bacillus subtilis and Salmonella typhimurium, as well as Neurospora crassa mitochondria and higher plant plastids . Thus the gene identified by the embryo-defective lethal insertion mutation encodes an RPS16 homolog and has been designated the SSR16 gene. FEMS Microbiol Lett, 1996 Sep 1, 142(2-3), 155 - 60 Role of ribosome degradation in the death of heat-stressed Salmonella typhimurium; Tolker-Nielsen T et al.; Heat treatment of Salmonella typhimurium results in cell death, which coincides with a significant reduction of the cellular content of 16S ribosomal RNA . It is suggested that the degradation of ribosomal RNA is a direct cause of cell death . This conclusion is based on the observation of carbon-starved and magnesium-supplemented cells, which survive heat treatment much better, and which also maintain stable levels of ribosomal RNA. J Appl Bacteriol, 1996 Sep, 81(3), 251 - 6 Effect of Saccharomyces boulardii against experimental oral infection with Salmonella typhimurium and Shigella flexneri in conventional and gnotobiotic mice; Rodrigues AC et al.; Saccharomyces boulardii was shown to be capable of inhibiting multiplication of enteropathogenic bacteria in vitro and is currently used for its anti-diarrhoea properties . We studied the capacity of this yeast to antagonize Salmonella typhimurium and Shigella flexneri in the intestinal tract of conventional or gnotobiotic NMRI mice . Conventional animals were given daily 10 mg doses of S . boulardii, whereas germ-free animals were given a single 10 mg dose . Both groups were challenged orally 5 d later with the pathogenic bacteria (10(8) or 10(2) viable cells, respectively) . Control groups were treated with saline instead of S . boulardii . Mortality and/or histopathological data showed a protective effect against the pathogenic bacteria in yeast-treated mice . Saccharomyces boulardii colonized the digestive tract of gnotobiotic mice and the number of viable cells ranged around 10(10) g-1 of faeces . In experimental and control gnotobiotic animals, Salm . typhimurium and Sh . flexneri became rapidly established at a level of about 10(10) viable cells g-1 of faeces and remained at high levels until the animals died or were sacrificed . The protection against Salm . typhimurium and Sh . flexneri obtained in conventional and/or gnotobiotic mice previously associated with S . boulardii is not due to the reduction of the bacterial populations in the intestines. J Bacteriol, 1996 Sep, 178(17), 5112 - 20 Identification of sigma S-regulated genes in Salmonella typhimurium: complementary regulatory interactions between sigma S and cyclic AMP receptor protein; Fang FC et al.; sigma S (RpoS)-regulated lacZ transcriptional fusions in Salmonella typhimurium were identified from a MudJ transposon library by placing the rpoS gene under the control of the araBAD promoter and detecting lacZ expression in the presence or absence of arabinose supplementation . Western blot (immunoblot) analysis of bacteria carrying PBAD::rpoS demonstrated arabinose-dependent rpoS expression during all phases of growth . sigma S-dependent gene expression of individual gene fusions was confirmed by P22-mediated transduction of the MudJ insertions into wild-type or rpoS backgrounds . Analysis of six insertions revealed the known sigma S-regulated gene otsA, as well as five novel loci . Each of these genes is maximally expressed in stationary phase, and all but one show evidence of cyclic AMP receptor protein-dependent repression during logarithmic growth which is relieved in stationary phase . For these genes, as well as for the sigma S-regulated spvB plasmid virulence gene, a combination of rpoS overexpression and crp inactivation can result in high-level expression during logarithmic growth . The approach used to identify sigma S-regulated genes in this study provides a general method for the identification of genes controlled by trans-acting regulatory factors. J Bacteriol, 1996 Sep, 178(17), 5092 - 9 Molecular basis of the magnesium deprivation response in Salmonella typhimurium: identification of PhoP-regulated genes; Soncini FC et al.; The PhoP-PhoQ two-component system is essential for virulence in Salmonella typhimurium . This system controls expression of some 40 different proteins, yet most PhoP-regulated genes remain unknown . To identify PhoP-regulated genes, we isolated a library of 50,000 independent lac gene transcriptional fusion strains and investigated whether production of beta-galactosidase was regulated by PhoP . We recovered 47 lac gene fusions that were activated and 7 that were repressed when PhoP was expressed . Analysis of 40 such fusions defined some 30 loci, including mgtA and mgtCB, which encode two of the three Mg2+ uptake systems of S . typhimurium; ugd, encoding UDP-glucose dehydrogenase; phoP, indicative that the phoPQ operon is autoregulated; and an open reading frame encoding a protein with sequence similarity to VanX, a dipeptidase required for resistance to vancomycin . Transcription of PhoP-activated genes was regulated by the levels of Mg2+ in a PhoP-dependent manner . Strains with mutations in phoP or phoQ were defective for growth in low-Mg2+ media . The mgtA and mgtCB mutants reached lower optical densities than the wild-type strain in low-Mg2+ liquid media but displayed normal growth on low-Mg2+ solid media . Six PhoP-activated genes were identified as essential to form colonies on low-Mg'+ solid media . Cumulatively, our experiments establish that the PhoP-PhoQ system governs the adaptation to magnesium-limiting environments. Infect Immun, 1996 Sep, 64(9), 3877 - 83 Rapid and complete fusion of macrophage lysosomes with phagosomes containing Salmonella typhimurium; Oh YK et al.; The virulence of Salmonella typhimurium for mice results, in part, from its ability to survive after phagocytosis by macrophages . Although it is generally agreed that intracellular bacteria persist in membrane-bound phagosomes, there remains some question as to whether these phagosomes fuse with macrophage lysosomes . This report describes the maturation of phagosomes containing S . typhimurium inside mouse bone marrow-derived macrophages . Macrophages were infected briefly and incubated for various intervals; then they were examined by fluorescence microscopy for colocalization of bacteria with lysosomal markers . These markers included LAMP-1, cathepsin L, and fluorescent proteins or dextrans preloaded into lysosomes by endocytosis . By all measures, phagosomes containing S . typhimurium merged completely with the lysosomal compartment within 20 min of phagocytosis . The rate of phagosome-lysosome fusion was similar to the rate for phagocytosed latex beads . Phagolysosomes remained accessible to fluid-phase probes and contained lysosomal markers for many hours . Moreover, a large percentage of the wild-type bacteria that were viable 20 min after infection survived longer incubations inside macrophages, indicating that the survivors were not a minor subpopulation that avoided phagosome-lysosome fusion . Therefore, we conclude that S . typhimurium survives within the lysosomal compartments of macrophages. Infect Immun, 1996 Sep, 64(9), 3811 - 7 Role of lipopolysaccharide in colonization of the mouse intestine by Salmonella typhimurium studied by in situ hybridization; Licht TR et al.; An avirulent, streptomycin-resistant Salmonella typhimurium strain, SL5319, and its lipopolysaccharide (LPS)-deficient mutant strain, SL5325, differ in their ability to colonize the large intestines of streptomycin-treated mice . When fed to mice independently, the strains colonize equally well, but when fed together, the LPS-deficient mutant is outcompeted by the wild-type strain during establishment in the gut (J.J . Nevola, B.A.D . Stocker, D.C . Laux, and P.S . Cohen, Infect . Immun . 50:152-159, 1985) . In the present study, the spatial distribution in the intestinal mucosal layer of the two strains was visualized by specific hybridization to bacterial rRNA in histological sections of mouse colon and cecum . The first day after infection, 9.8% of the smooth SL5319 cells observed in mucus were found to be associated with the mouse epithelial cells, but three days after infection, the corresponding fraction of adhering bacteria was reduced to 2.1% . The LPS-deficient S . typhimurium strain was confined to the part of the mucosal layer closest to the colonic lumen and was not observed to adhere to the epithelium either at day 1 or 3 after infection . Quantitative determinations of the distance from the S . typhimurium cells to the epithelial wall confirmed that the average distance for the rough S . typhimurium SL5325 was much larger than for its smooth counterpart, S . typhimurium SL5319 . Quantification of the hybridization signal from bacteria isolated from the cecal mucus revealed that the two strains had the same ribosome concentration, indicating that they have the same potential for growth in the intestinal environment . On the basis of these observations, we suggest that the better colonization ability of the strain carrying wild-type LPS is due to the better abilities to penetrate the intestinal mucosal layer and to subsequently bind to the epithelial cells in vivo. Infect Immun, 1996 Sep, 64(9), 3786 - 92 Attenuated Salmonella vaccine-induced suppression of murine spleen cell responses to mitogen is mediated by macrophage nitric oxide: quantitative aspects; Huang D et al.; Previous reports from our laboratory have shown that 7 days after infection of C3HeB/FeJ mice with an attenuated strain of Salmonella typhimurium, there is profound suppression of responses to B- and T-cell mitogens and suppression of the capacity of spleen cells to mount a primary, in vitro plaque-forming-cell (PFC) response to sheep erythrocytes . Inhibition of the PFC response was shown to be mediated by nitric oxide (NO), as NG-monomethyl-L-arginine (NMMA) gave complete reversal of suppression . The experiments reported here examined the role of NO in suppression of the response to the mitogen concanavalin A (ConA) . In contrast to the PFC system, it was found that addition of NMMA to ConA-stimulated immune spleen cells resulted in less than 20% reversal of suppression . However, addition to NMMA resulted in a 50% reversal of suppression in cocultures of immune and normal spleen cells at a ratio of 1:4 . A complete restoration of ConA-induced responses was achieved in cocultures incubated in medium containing a reduced concentration of L-arginine plus 1.25 mM NMMA . Investigation of why NMMA alone was not 100% effective in reversing suppression showed that addition of ConA significantly augmented production of nitrite and gamma interferon (IFN-gamma) in cocultures containing immune cells . Addition of anti-IFN-gamma reduced nitrite levels in the cultures, although results with the combination of anti-IFN-gamma and NMMA were not significantly better than results with NMMA alone . These findings suggest that suppression in cultures stimulated with ConA is difficult to reverse completely with NMMA alone because of an overproduction of NO, which can be offset by either reducing the L-arginine concentration or blocking IFN-gamma . The quantitative relationship between nitrite levels and suppression in cocultures was examined . It was found that suppression did not correlate directly with the nitrite concentration but rather with the log10 of the nitrite concentration . Nitrite levels above 15 microM gave almost complete suppression, and levels between 1 and 10 microM gave a wide range of suppression . These results strongly support NO as the suppressor factor in Salmonella-induced immunosuppression of responses to ConA and, by inference, suppression of responses to mitogens induced by other microbes . The results show that involvement of NO cannot always be demonstrated by simple addition of NMMA to suppressed mitogen-stimulated spleen cell cultures. Infect Immun, 1996 Sep, 64(9), 3524 - 31 Requirement for exported proteins in secretion through the invasion-associated type III system of Salmonella typhimurium; Collazo CM et al.; The inv and spa loci of Salmonella typhimurium encode a type III protein secretion system which is essential for the ability of this microorganism to gain access to cultured epithelial cells . These loci are located at centisome 63 in the Salmonella chromosome . We have carried out a functional analysis of several genes of these loci and have found that two exported proteins encoded in this region, InvJ and SpaO, are required for secretion through the invasion-associated type III secretion system . These findings suggest the existence of a hierarchy in the export process, since mutations in other targets of this secretory system have no effect on protein secretion . We have also shown that the spaO, spaP, spaQ, and spaR genes are required for protein secretion and for the ability of S . typhimurium to gain access to cultured epithelial cells . In addition, we investigated the ability of an invJ S . typhimurium mutant strain to present the SipB protein to the bacterial surface and demonstrated that, in contrast to Spa32, its putative Shigella homolog, InvJ is not involved in the surface presentation of the Sip proteins. Pediatr Cardiol, 1996 Sep-Oct, 17(5), 330 - 1 Fatal Salmonella typhimurium infection of a vascular graft in an infant; Juneja R et al.; A case of Salmonella typhimurium endocarditis of a Blalock-Taussig shunt in an infant is described for its rarity . Wider appreciation of such infections is warranted. Biophys Chem, 1996 Aug 30, 61(1), 9 - 22 Time-resolved fluorescence of tryptophan synthase; Vaccari S et al.; Time-resolved and steady-state fluorescence of the tryptophan synthase alpha 2 beta 2 complex and of the beta 2 dimer from Salmonella typhimurium were measured to characterize the conformational properties of the beta subunit in the presence and in the absence of the alpha subunit when the catalytic species internal aldimine, external aldimine and alpha-aminoacrylate Schiff bases were selectively accumulated within the beta active site . The fluorescence decay of the coenzyme pyridoxal 5'-phosphate, bound via a Schiff base in the beta subunit of the alpha 2 beta 2 complex (internal aldimine species), is accounted for by two lifetimes (2.9 and 0.9 ns) of almost equal fractional intensity that are slightly affected by pH . Accordingly, both the absorption and emission spectra were found to be pH independent . The emission properties of the internal aldimine in the beta 2 dimer are pH dependent, suggesting that the alpha-subunit binding alters the microenvironment of the beta-subunit active site . This conclusion is also supported by the emission of the single tryptophanyl residue of the enzyme (Trp-177 beta) . In the reaction of L-serine with the alpha 2 beta 2 complex, the predominant catalytic intermediate is the external aldimine (lambda(max) = 422 nm) at pH 10, and the alpha-aminoacrylate (lambda(max) = 350 nm) at pH 7 . The external aldimine exhibits a high fluorescence intensity at 500 nm that decays with a single lifetime of 6.2 ns in the alpha 2 beta 2 complex, at pH 10, and at a similar value in the beta 2 dimer . The emission properties of the external aldimine with respect to the internal aldimine, and the small effects induced by alpha-subunit binding indicate a shielding of the coenzyme and a stabilization of its excited state . In contrast, the short fluorescence lifetime (0.4 ns) and the weak fluorescence emission of the alpha-aminoacrylate Schiff base indicate an increase of non-radiative processes possibly due to a more tight coupling of this intermediate with the protein matrix with respect to the external aldimine . Whereas the internal aldimine is distributed in two tautomeric forms, both the external aldimine and the alpha-aminoacrylate are present in single conformational states with distinct structural and/or dynamic properties that may modulate regulatory intersubunit signals. J Biol Chem, 1996 Aug 30, 271(35), 21243 - 50 Ligand-dependent conformational plasticity of the periplasmic histidine-binding protein HisJ . Involvement in transport specificity; Wolf A et al.; The periplasmic histidine permease of Salmonella typhimurium is composed of a membrane-bound complex and a soluble histidine-binding protein (the periplasmic receptor), HisJ . Liganded receptor interacts with the membrane-bound complex, inducing ATP hydrolysis and substrate translocation . Preliminary evidence had shown a lack of direct correlation between the affinity of HisJ for a ligand and translocation efficiency, suggesting that the precise form of the receptor is important in determining its interaction with the membrane-bound complex . We have investigated the nature of the conformations assumed by HisJ upon binding a variety of ligands by tryptophan fluorescence enhancement, reaction with a closed form-specific monoclonal antibody, and changes in UV absorption spectra . It is demonstrated that although HisJ binds all the ligands and undergoes a conformational change, it assumes measurably different conformations . We also show that the interaction between HisJ and the membrane-bound complex depends on the nature of the ligand . Transport specificity appears to be defined, at least in part, by the conformation of the bound receptor, manifested either by the effect of a given ligand on the closed structure per se, or by the effect of ligand association on the equilibrium constant relating the open and the closed liganded forms. J Mol Biol, 1996 Aug 16, 261(2), 195 - 208 FliN is a major structural protein of the C-ring in the Salmonella typhimurium flagellar basal body; Zhao R et al.; The Salmonella typhimurium FliN protein has been proposed to form a mutually interacting complex with FliG and FliM, the switch complex, that is required for flagellar morphogenesis and function . We have used affinity chromatography for purification of extended flagellar basal bodies sufficient for quantitative analysis of their protein composition . The belled, extended structure is predominantly comprised of the switch complex proteins; with FliN present in the most copies (111 +/- 13) . This explains why single, missense fliN, fliG or fliM mutations, found in many non-motile strains, can alter the belled morphology . Cell lysates from these strains contained the wild-type complement of FliG, FliM and FliN; but the basal bodies lacked the outer, cytoplasmic(C)-ring of the bell and were separated by sedimentation from FliM and FliN . The amount of FliG present in basal bodies from wild-type and one such mutant, FliN100LP, was comparable . These data show that: (1) the mutations define a FliG and FliMFliN multiple contact interface important for motility . (2) FliG is responsible for the increased size of the membrane-embedded MS-ring complex of belled relative to acid-treated basal bodies . (3) FliN, together with FliM, account for most of the C-ring . As a major component of the C-ring, FliN is distinct from the other proteins implicated in axial flagellar protein export . Inner, cytoplasmic rod basal substructure, seen by negative-stain and quick-freeze replica electron microscopy, may gate such export . Lack of connectivity between the cytoplasmic rod and ring substructures places contacts between FliG and FliMFliN at the periphery of the basal body, proximal to the flagellar intramembrane ring particles . This topology is consistent with models where torque results from interaction of circumferential arrays of the switch complex proteins with the ring particles. Eur J Biochem, 1996 Aug 15, 240(1), 63 - 70 A thermodynamic analysis of conformational change due to the alpha 2 beta 2 complex formation of tryptophan synthase; Hiraga K et al.; A characteristic property of the tryptophan synthase alpha 2 beta 2 complex is the mutual activation of the alpha and beta subunit upon complex formation . It has been speculated that this mutual activation results from the conformational change due to the alpha/beta subunit interaction . To elucidate this mechanism, we investigated the thermodynamic parameters of association for the various combinations of the alpha and beta subunits from Escherichia coli and Salmonella typhimurium using isothermal titration calorimetry . The negative association enthalpy of the S . typhimurium alpha subunit with the beta subunit from E . coli (or S . typhimurium) was about 20 kJ mol-1 larger than that of the E . coli alpha subunit at 40 degrees C . However, the favorable enthalpy of the S . typhimurium alpha subunit was perfectly compensated by the unfavorable association entropy, therefore, the Gibbs energy of association was similar to that of the E . coli alpha subunit . Furthermore, the site-directed mutagenesis study revealed that a single mutation (K109N; {Asn109} alpha subunit) of the E coli alpha subunit at the subunit interface from E . coli to the S . typhimurium type could change the characteristics of the thermodynamic parameters of association to the S . typhimurium alpha subunit type . The heat-capacity changes of the association of the alpha subunit with the beta subunit were quite great, 6.37-8.21 kJ mol-1 K-1, compared with that due to a decrease in accessible surface area in the subunit interface . The analysis of the thermodynamic parameters of association suggested that the complex formation couples with the folding (rearrangements) of the alpha subunit monomer or/and beta subunit dimer. Mutat Res, 1996 Aug 12, 369(3-4), 195 - 208 The Salmonella sulA-test: a new in vitro system to detect genotoxins; el Mzibri M et al.; The Salmonella sulA-test is a newly developed colorimetric assay to detect genotoxins . This technique is based on the ability of DNA-damaging agents to induce the sulA gene, one of the SOS response genes . A constructed plasmid, pEM1968, carrying a fused sulA'::'lacZ was introduced into Salmonella typhimurium TA1538 . Monitoring sulA gene expression was performed by assaying the beta-galactosidase activity in the transformed strain S . typhimurium TA1538/pEM1968 . A simple, fast and sensitive liquid incubation procedure has been developed after optimization of the S9 mix composition and beta-galactosidase assay . The SOS-inducing potency (SOSIP, microM-1) was defined as the slopes of the non-linear dose-response relationships . Twenty-one chemicals with different modes of action were examined for a preliminary evaluation of the test . Nineteen chemicals were genotoxic in the Salmonella sulA-test . The SOSIP ranged from 1.2 x 10(-4) microM-1 (ethyl methanesulfonate) to 419.9 microM-1 (bleomycin) . Sodium azide and 5-fluorouracil were not genotoxic . Frameshift, base-pair and oxidative genotoxins were detected by the tester strain . The calculated SOSIP and the minimum concentrations detected (MCD) in the Salmonella sulA-test were compared to the reported values obtained with two similar assays: the SOS Chromotest and umu-test . The SOSIP values of 12 compounds were the highest in this new assay . Five chemicals tested in the Salmonella sulA-test gave similar SOSIP values with those of one of the two other tests . ICR-191 had the highest SOSIP with the SOS Chromotest and 3-methylchloranthrene showed the highest SOSIP with the umu-test . Similarly, the lowest MCD values were found for 12 compounds in the Salmonella sulA-test . Four compounds had close MCD values in this assay and one of the two other techniques . The SOS Chromotest remained the most sensitive assay for cisplatin and ICR 191 . The umu-test was the technique of choice for 3-methylchloranthrene. Mutat Res, 1996 Aug 12, 369(3-4), 183 - 94 Effects of beta-carotene and alpha-tocopherol on photogenotoxicity induced by 8-methoxypsoralen: the role of oxygen; Bianchi L et al.; The protective effect of beta-carotene (beta-C) and alpha-tocopherol (alpha-T), singularly and in equimolar mixtures, toward the photomutagenicity induced by 8-methoxypsoralen (8-MOP), at different oxygen partial pressure (pO2), was evaluated in two different experimental models: Salmonella typhimurium TA102 and Saccharomyces cerevisiae D7 . After phototreatment with 8-MOP, the results show a lethal effect under hypoxic conditions in both experimental model systems, an increase in revertants associated to the pO2 increase in S . typhimurium TA102, and a decrease in revertants and convertants associated to the pO2 increase in S . cerevisiae D7 . In S . typhimurium TA102, in atmospheric condition, beta-C and alpha-T (1.86 or 18.6 microM) show a protective effect only at the higher dosage . Alpha-T was more protective than beta-C . The equimolar mixtures show an antimutagenic effect at both dosage used with a synergistic effect at lower dosage and an additive antimutagenic activity at higher dosage . An inhibition of the spontaneous mutagenicity by mixtures at higher dosage was also observed . The results obtained in S . typhimurium TA102 show an antimutagenic effects of beta-C, alpha-T and their mixture at 190 mmHg pO2, confirming the data obtained in air condition . At 380 mmHg pO2, alpha-T and the mixture show a significant antimutagenic activity; at 570 mmHg pO2, only alpha-T is protective . At 760 mmHg pO2, no protective effect was observed by the two antioxidants, and beta-C increases the photomutagenicity induced by 8-MOP . In S . cerevisiae D7 a protective effect was only observed at 380 mmHg pO2 with the mixture . No antigenotoxic effect was found in the other experimental conditions, even if the uptake of the two antioxidants was confirmed by HPLC . Our results underline the role of oxygen in the photomutagenicity induced by 8-MOP and in the antimutagenic activity of beta-C and alpha-T . This is the first report confirming in a cellular experimental model the data obtained in some chemical systems: the protective effect of beta-C only at low pO2 and the synergistic effect of mixture of beta-C and alpha-T. Mutat Res, 1996 Aug 8, 360(3), 165 - 71 The mutagenicities of alkaloids and N-nitrosoguvacoline from betel quid; Wang CK et al.; In Taiwan, betel quid is a natural masticatory, which is composed of fresh green areca fruit, Piper betle and slaked lime paste . Areca fruit contains some alkaloids, of which arecoline is the major one . N-Nitrosoguvacoline (NG), one of the N-nitrosation products of arecoline, is the only one N-nitrosamine found in Taiwanese betel quid chewing saliva . The mutagenic studies in Ames Salmonella microsome test showed that crude alkaloid extracts of areca fruit and arecoline were active in Salmonella typhimurium TA100, and NG was weakly active in TA98 and TA100 . The activities in both arecoline and NG decreased further in the presence of rat liver S9 mix . Nitrite was significantly consumed during the N-nitrosation of arecoline and sodium nitrite at acidic condition (pH 3), whereas the formation of NG was favored at neutral condition (pH 7) . Crude phenolic extracts of leaf and inflorescence of Piper betle inhibited the formation of NG by blocking the nitrite . However, a high amount of crude phenolic extracts of areca fruit enhanced the formation of NG. Biochemistry, 1996 Aug 6, 35(31), 10031 - 40 Identification of retained N-formylmethionine in bacterial recombinant mammalian cytochrome P450 proteins with the N-terminal sequence MALLLAVFL...: roles of residues 3-5 in retention and membrane topology; Dong MS et al.; An N-terminal block to Edman degradation was observed when any of five different mammalian cytochrome P450 (P450) proteins was expressed in Escherichia coli using the N-terminal sequence MALLLAVFL.. . This block was also seen in Salmonella typhimurium . With all proteins examined, the block could be removed by mild acid hydrolysis (0.6--6 N HCl, 23 degrees C) to expose Met as the N-terminus, suggesting N-formylMet retention . The N-terminal peptide of a modified P450 1A2 ("mutant 1", containing a thrombin-sensitive site inserted at residue 25) was released with thrombin and analyzed by electrospray mass spectrometry and found to yield the M(r) expected for the N-formyl derivative (+/- 0.8 amu) . The region of positions 3--5 was altered by random mutagenesis, and three P450 1A2-expressing clones were analyzed for nucleotide and amino acid sequences . The changes from LLL were to RER (P450 1A2a), VDS (P450 1A2b), and WRH (P450 1A2c); these all show slightly dissimilar hydropathy plots compared to the MALLLAVFL.. . sequence . Mutant P450 1A2a had the N-terminal Met removed to yield N-terminal Ala; P450 1A2b contained an unmodified Met at the N-terminus; P450 1A2c had an approximately 80% block of the N-terminal Met . Experiments with bacterial membranes containing expressed P450 1A2 mutant 1 and P450 1A2 mutant 2 (thrombin-sensitive site inserted at residue 46) suggest that thrombin site 2, but not 1, is sequestered in the membrane . Spheroplasts of bacteria expressing P450 1A2 and the mutants at positions 3--5 were treated with proteinase K; amino acid analysis indicated that no cleavage occurred . These results are interpreted in a model in which most of the mammalian P450 expressed in the bacterium is located in the cytosol, the region near residue 46 is in the inner membrane, the region near residue 25 is in the cytosol, and the N-terminus is either imbedded in the membrane or free in the cytosolic space, depending upon the sequence . However, the possibility that the differences in N-terminal processing are the result of direct changes in interactions with the deformylase and Met aminopeptidase cannot be excluded. Front Biosci, 1996 Aug 01, 1, d131 - 45 New insights on molecular pathways utilized by salmonella species in cell binding; McCormick BA et al.; Salmonella infections are a principal source of gastroenteritis and enteric fever in a variety of animals, including humans . An essential step in the development of Salmonella pathogenesis is the entry of bacteria into non-phagocytic cells, including those that line the intestinal epithelium . As a consequence of specific cues from the host intestinal micro-environment, Salmonella entry into the intestinal epithelium is the product of a multistep process that culminates in host cell membrane ruffling, and subsequent bacterial uptake . The events that trigger the internalization event appear to require an array of bacterial secreted proteins, exemplified by the formation of bacterial surface appendages (invasomes) which are important for the induction of host-cell signal transduction pathways that lead to membrane ruffling . In addition, during intestinal disease states induced by Salmonella typhimurium, transepithelial migration of neutrophils rapidly follows attachment of the bacteria to the epithelial membrane . Current evidence indicates that the intestinal epithelium plays a key role in orchestrating the inflammatory response to surface attached S . typhimurium . In this review, we explore current insights on the molecular pathways utilized by Salmonella spp . in cell binding that are important not only in the processes of Salmonella internalization but also in the generation of signals which lead to active states of intestinal inflammation. Vet Med (Praha), 1996 Aug, 41(8), 255 - 9 {Use of hydrated lime for disinfection of sewage sludge containing Salmonella typhimurium and Ascaris suum as model pathogens}; Plachy P et al.; Hydrated lime was lethal to the strain of Salmonella typhimurium (Sk 14/39) after 60 min of exposure . In the control without addition of hydrated lime this strain was still viable after 168 hours, counting 6.1 x 10(5) pathogens/l ml sludge . 168-hr disinfection of primary sludges with 10 g/l hydrated lime showed no significant reduction in the viability of Ascaris suum eggs . In three experiments, the number of viable eggs was reduced only by 3.6% . Indicator microorganisms, except psychrophilic ones that survive for only 24 hr, were destroyed after 60 min of exposure . The temperature of stabilized sludges did not vary considerably during experiments, ranging between 21 and 25 degrees C . With the addition of Ca(OH)2, sludge pH increased to the values for COD, organic matters and total nitrogen were reduced throughout the experiments . The values for sludge dry residues remained unchanged. Immunopharmacology, 1996 Aug, 34(1), 1 - 7 Recombinant human prolactin induces protection against Salmonella typhimurium infection in the mouse: role of nitric oxide; Meli R et al.; In the present study, we demonstrated that repeated treatment with recombinant human prolactin (rhPRL) protected mice against Salmonella typhimurium infection . The protective activity was statistically significant, dose-dependent and present only when rhPRL treatments were performed before the infection . This activity was probably related to the observed increases in phagocytosis and intracellular killing of peritoneal macrophages induced by the hormonal treatment . The number of peripheral leukocytes was not modified, excluding a mobilization of cells from other compartments . A decrease in the mortality rate after challenge was also observed in mice treated with the monoclonal antibody anti-PRL receptor U5, confirming that the protective activity was associated with receptor activation . Our studies also suggest that nitric oxide (NO) production was involved in the protective effect of rhPRL since pre-treatment of the animals with L-NAME, an inhibitor of NO-synthase, was able to completely revert the protective activity, whereas D-NAME, the inactive D-isomer, was without effect. Biochem Mol Biol Int, 1996 Aug, 39(6), 1157 - 65 Purification of an alpha,beta-ketoalkene double bond reductase from Salmonella typhimurium; Ishida M et al.; An alpha, beta-ketoalkene double bond reductase was purified from the cell-free extract of Salmonella typhimurium . The purified enzyme was homogeneous by the criterion of sodium dodecyl sulfate-polyacrylamide gel electrophoresis . The molecular weight of the enzyme was estimated to be 24,700 by the electrophoresis and 23,900 by HPLC gel filtration, respectively . The isoelectric point is pH 7.2 . The enzyme in the presence of NAD(P)H exhibited double bond reductase activity toward alpha, beta-ketoalkenes such as trans-phenyl-1-propenyl ketone, trans-benzylideneacetophenone and 15-ketoprostaglandins . The enzyme activity was markedly inhibited by dicumarol. Int J Pancreatol, 1996 Aug, 20(1), 51 - 7 Mutagenic activation of N-nitrosobis(2-oxopropyl)amine by pancreatic juice and assessment of its ductal tumorigenicity following intraductal administration in dogs; Kamano T et al.; CONCLUSION: The results suggest that systemic administration (s.c . and i.p.) of BOP induces liver damage due to BOP itself and/or its metabolites which might be formed in the liver and that interaction of BOP itself in the pancreatic duct with pancreatic juice plays an important role for pancreatic duct tumorigenicity . METHODS: Mutagenic activation and pancreatic duct tumorigenicity of N-nitrosobis (2-oxopropyl)amine (BOP) administered s.c., i.p., and i.d . were studied in dogs . RESULTS: Following i.p . administration of BOP, N-nitroso(2-hydroxypropyl) (2-oxopropyl)amine (HPOP) and N-nitrosobis(2-hydroxypropyl)amine (BHP), but not BOP, were detected in pancreatic juice, while following i.d . administration, only BOP was detected . The pancreatic juice of one dog that received 100 mg of BOP i.d . showed positive mutagenicity towards Salmonella typhimurium TA100, but the pancreatic juice of two dogs that received 100 mg of BOP i.p . was not mutagenic . BOP showed clear mutagenicity in the presence of pancreatic juice from untreated dogs, but the pancreatic juice could not activate HPOP and BHP to mutagens . BOP administered sc for 2 wk (total dose: 600 mg) induced clinical toxicity, nausea, vomiting, and loss of appetite at 10 wk . BOP administered i.p . for 4 mo (total dose: 2000 mg) induced liver damage at 6 mo, but no pancreatic injury . BOP administered i.d . for 6.5 or 12 mo (total dose: 2500 or 4700 mg, respectively) induced papillary hyperplasia and dysplasia of duct epithelial cells and ductal proliferation with fibrosis. Mol Microbiol, 1996 Aug, 21(3), 633 - 41 A secreted protein tyrosine phosphatase with modular effector domains in the bacterial pathogen Salmonella typhimurium; Kaniga K et al.; A number of bacterial pathogens have evolved sophisticated strategies to subvert host-cell signal-transduction pathways for their own benefit . These bacteria produce and export proteins capable of specific interactions with key mammalian cell regulatory molecules in order to derail the normal functions of the cells . In this study, we describe the identification of a modular effector protein secreted by the bacterial pathogen Salmonella typhimurium that is required for its full display of virulence . Sequence analysis revealed that a carboxy-terminal region of this protein, which we have termed SptP, is homologous to the catalytic domains of protein tyrosine phosphatases . Purified SptP protein efficiently dephosphorylated peptide substrates phosphorylated on tyrosine . An engineered mutant of SptP in which a critical Cys residue in the catalytic domain was changed to Ser was devoid of phosphatase activity, indicating a catalytic mechanism similar to that of other tyrosine phosphatases . In addition, an amino-terminal region of SptP exhibited sequence similarity to the ribosyltransferase exoenzyme S from Pseudomonas aeruginosa and the cytotoxin YopE from Yersinia spp . The modular nature of this effector protein may allow multiple interactions with host-cell signalling functions. Mutat Res, 1996 Aug, 370(1), 39 - 47 Genotoxicity of 4-chloro-o-toluidine in Salmonella typhimurium, human lymphocytes and V79 cells; Goggelmann W et al.; In the absence of a metabolizing system (S9 mix) 4-chloro-o-toluidine (4-COT) was found to be ineffective in a combination of assays for gene mutations in Salmonella typhimurium, for chromosome aberrations and sister chromatide exchanges in human lymphocytes, and for the induction of spindle disturbances in V79 Chinese hamster cells . In the presence of S9, 4-COT was also ineffective in producing structural or numerical changes in mammalian cells, but the yields of 4-COT induced revertants in S . typhimurium strains TA 100 and TA 98 were about 2-fold higher than those in controls. Mutat Res, 1996 Aug, 370(1), 11 - 7 Suppressive effects of chlorophyllin on mutagen-induced umu C gene expression in Salmonella typhimurium (TA 1535/pSK 1002) and tumor promoter-dependent ornithine decarboxylase induction in BALB/c 3T3 fibroblast cells; Okai Y et al.; The potentially protective role of chlorophyllin, the sodium and copper salt of chlorophyll a against the initiation and promotion stages in carcinogenesis was studied by in vitro short-term assays . Chlorophyllin showed a dose-dependent suppressive effect on 3-amino-1,4-dimethyl-5H-pyrido{4,3-b}indol (Trp-P-1)-induced umu C gene expression of Salmonella typhimurium (TA 1535/pSK 1002) in the presence of metabolizing enzyme mixture . The similar inhibitory effect of chlorophyllin was detected in mitomycin C (MMC)-dependent umu C gene expression in the absence of metabolizing enzyme mixture . Furthermore chlorophyllin also exhibited a dose-dependent inhibition on 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-induced ornithine decarboxylase (ODC) activity of 3T3 fibroblast cells at the same concentrations . However, when chlorophyll a isolated from Japanese tea leaves was applied on the same assay systems as a comparative experiment, chlorophyll a showed much weaker activity compared with that of chlorophyllin . The significance of this finding is discussed from the viewpoint of the protective role of chlorophyllin against carcinogenesis. Protein Expr Purif, 1996 Aug, 8(1), 126 - 36 PCR mutagenesis and overexpression of tryptophan synthase from Salmonella typhimurium: on the roles of beta2 subunit Lys-382; Yang L et al.; We have devised convenient methods for mutagenesis and very high level expression of wild type and mutant tryptophan synthase alpha and beta2 subunits and alpha2beta2 complex from Salmonella typhimurium . The trpBA genes were modified by introduction of five new restriction sites by polymerase chain reaction (PCR) and were then cloned into the plasmid pTrc99A under trc promoter control . The recombinant plasmid pEBA-10 and three plasmids constructed from pEBA-10 were transformed into Escherichia coli CB149, which lacks tryptophan operon genes . Optimization of growth conditions of the transformed cells resulted in 10- to 40-fold higher yields of cells ( approximately 22 g/liter) than attained previously . The improved expression system gave higher yields of tryptophan synthase proteins (23-70% of the soluble protein) and led to correspondingly high yields of purified alpha and beta2 subunits or alpha2beta2 complex (200-800 mg/liter) . A plasmid containing 8 copies of the trpA gene gave the highest yield of alpha subunit . The PCR-based mutagenesis method permits mutation of any base pair in the trpBA genes, between suitable pairs of restriction sites, and requires only one new primer per mutation . The method is illustrated by construction of mutant beta2 subunits with any of five amino acid substitutions at Lys-382, the site of a previously described missense mutation . Characterization of the purified mutant alpha2beta2 complexes shows that Lys-382 in the wild type alpha2beta2 complex does not serve an essential catalytic role but may stabilize an active "closed" conformation of the enzyme by forming a salt bridge with Glu-350. Can J Microbiol, 1996 Aug, 42(8), 855 - 8 Identification of two core types in lipopolysaccharides of Actinobacillus pleuropneumoniae representing serotypes 1 to 12; Jacques M et al.; Lipopolysaccharides (LPS) of Actinobacillus pleuropneumoniae were separated by Tricine-SDS-polyacrylamide gel electrophoresis, which has been shown to improve resolution of low-molecular-mass fast migrating bands . Strains representing the 12 serotypes of A . pleuropneumoniae can be divided in two groups according to the gel mobility of the core - lipid A region of their LPS . The first electromorphic core type (core type I), found in serotypes 1, 6, 9, and 11, had a migration slower than Salmonella typhimurium Ra LPS . The second electromorphic core type (core type II), found in the remaining serotypes (i.e., 2, 3, 4, 5, 7, 8, 10, and 12) had a migration similar to S . typhimurium Ra LPS . Furthermore, we observed that these two core types were antigenically different . Western blot analyses indicated that core - lipid A region of LPS from electromorphic core type I strains reacted when probed with serum from a pig experimentally infected with a core type I strain but not when probed with serum from a pig experimentally infected with a core type II strain . Conversely, core - lipid A region of LPS from electromorphic core type II strains reacted only when probed with serum from a pig experimentally infected with a core type II strain . Our results, based on both electrophoretic mobility and antigenicity, suggest the presence of two LPS core types in A . pleuropneumoniae. J Appl Bacteriol, 1996 Aug, 81(2), 188 - 90 Inhibition of Salmonella typhimurium by the products of tartrate metabolism by a Veillonella species; Hinton A Jr et al.; The inhibition of the growth of Salmonella typhimurium by a Veillonella species grown on media supplemented with tartrate was examined . Growth of Salmonella typhimurium was not inhibited by the concentrations of products metabolized by Veillonella cultures on media supplemented with 0 or 50 mmol l-1 of tartrate, but was inhibited on media supplemented with 100 or 150 mmol l-1 of tartrate . Inhibition of Salm . typhimurium was correlated with the increased production of acetate and propionate from tartrate by the Veillonella species. J Bacteriol, 1996 Aug, 178(16), 5032 - 8 Proteome of Salmonella typhimurium SL1344: identification of novel abundant cell envelope proteins and assignment to a two-dimensional reference map; Qi SY et al.; Forty-nine cell envelope proteins of Salmonella typhimurium SL1344 have been identified by microsequencing and assigned to a two-dimensional reference map . Ten of the sequenced proteins appear to be novel . Several others closely match currently hypothetical proteins or proteins found in other bacteria but not previously reported in salmonellae. Infect Immun, 1996 Aug, 64(8), 3385 - 93 The Salmonella virulence plasmid enhances Salmonella-induced lysis of macrophages and influences inflammatory responses; Guilloteau LA et al.; The Salmonella dublin virulence plasmid mediates systemic infection in mice and cattle . Here, we analyze the interaction between wild-type and plasmid-cured Salmonella strains with phagocytes in vitro and in vivo . The intracellula