Infect Immun, 1998 Nov, 66(11), 5295 - 300 Inhibition of Salmonella typhimurium invasion by host cell expression of secreted bacterial invasion proteins; Carlson SA et al.; Pathogenic Salmonella species initiate infection of a host by inducing their own uptake into intestinal epithelial cells . An invasive phenotype is conferred to this pathogen by a number of proteins that are components of a type III secretion system . During the invasion process, the bacteria utilize this secretion system to release proteins that enter the host cell and apparently interact with unknown host cell components that induce alterations in the actin cytoskeleton . To investigate the role of secreted proteins as direct modulators of invasion, we have evaluated the ability of Salmonella typhimurium to enter mammalian cells that express portions of the Salmonella invasion proteins SipB and SipC . Plasma membrane localization of SipB and SipC was achieved by fusing carboxyl- and amino-terminal portions of each invasion protein to the intracellular carboxyl-terminal tail of a membrane-bound eukaryotic receptor . Expression of receptor chimeras possessing the carboxyl terminus of SipB or the amino terminus of SipC blocked Salmonella invasion, whereas expression of their chimeric counterparts had no effect on invasion . The effect on invasion was specific for Salmonella since the perturbation of uptake was not extended to other invasive bacterial species . These results suggest that Salmonella invasion can be competitively inhibited by preventing the intracellular effects of SipB or SipC . In addition, these experiments provide a model for examining interactions between bacterial invasion proteins and their host cell targets. Zh Mikrobiol Epidemiol Immunobiol, 1998 Jul-Aug, (4), 19 - 23 {The design and study of an ogt deletion mutant of Salmonella typhi}; Satorov S et al.; The chromosome of S . typhi, similarly to those of Escherichia coli and Salmonella typhimurium, was found to contain ogt gene . Using Cmr gene, flanked by the corresponding sites of Salmonella chromosome, we managed to create S . typhi ogt deletion mutant strain . As shown in this study, ogt gene, together with giving protection against alkylating, methylating, ethylating and propylating agents, played an important role in protection against other mutagenic factors . In contrast to the wild strain, S . typhi ogt deletion mutant strain was found to be sensitive to UV radiation, pesticides and antimicrobial preparations. Microbiology, 1998 Sep, 144 ( Pt 9), 2497 - 504 Hydrolysis of the soft amphiphilic antimicrobial agent tetradecyl betainate is retarded after binding to and killing Salmonella typhimurium; Ahlstrom B et al.; Hydrolysis of tetradecyl betainate (B14), a fast-acting microbicidal amphiphilic quaternary ammonium compound (QAC) being an ester of betaine and tetradecanol, occurred after binding to Salmonella typhimurium, resulting in release of the water-soluble betaine portion and retention of the lipophilic tetradecanol . The rate of the hydrolysis was significant but retarded in comparison to B14 in solution . As in free solution, the hydrolysis of substance bound to S . typhimurium was increased in an alkaline environment and by heat . At pH 6.0 and 20 degrees C the hydrolysis of bound ester was about 10% after 180 min, whereas at pH 9.0 and 50 degrees C it was about 50% after 60 min . These results are consistent with a model where amphiphilic QACs are inserted into the bacterial outer membrane (OM) with the quaternary ammonium head group facing outwards and the lipophilic portion, including the ester bond, being in the membrane lipid environment enough for retarding the hydrolysis . However, calculation of the mean concentration of B14 in the bacteria at MBC99 (minimum bactericidal concentration required to kill 99% of cells) showed a 7000-8000 times greater concentration than in the medium . At this concentration, when most B14 is considered to be bound to the OM, the available surface area for each molecule was only 2 A2 . This is only 6-7% of that required for close packing of the quaternary ammonium head group (30 A2), indicating that a three-dimensional, presumably continuous arrangement was formed . Since B14 is hydrolysed after its binding to bacteria with microbicidal effect, it may be used under conditions where stable QACs might be harmful to the close or the common environment. Mol Microbiol, 1998 Sep, 29(6), 1471 - 80 The identification of exported proteins with gene fusions to invasin; Worley MJ et al.; Exported proteins are integral to understanding the biology of bacterial organisms . They have special significance in pathogenesis research because they can mediate critical interactions between pathogens and eukaryotic cell surfaces . Further, they frequently serve as targets for vaccines and diagnostic tests . The commonly used genetic assays for identifying exported proteins use fusions to alkaline phosphatase or beta-lactamase . These systems are not ideal for identifying outer membrane proteins because they identify a large number of inner membrane proteins as well . We addressed this problem by developing a gene fusion system that preferentially identifies proteins that contain cleavable signal sequences and are released from the inner membrane . This system selects fusions that restore outer membrane localization to an amino terminal-truncated Yersinia pseudotuberculosis invasin derivative . In the present study, a variety of Salmonella typhimurium proteins that localize beyond the inner membrane were identified with gene fusions to this invasin derivative . Previously undescribed proteins identified include ones that share homology with components of fimbrial operons, multiple drug resistance efflux pumps and a haemolysin . All of the positive clones analysed contain cleavable signal sequences . Moreover, over 40% of the genes identified encode putative outer membrane proteins . This system has several features that may make it especially useful in the study of genetically intractable organisms. Mol Microbiol, 1998 Sep, 29(6), 1435 - 48 Gyrase and Topo IV modulate chromosome domain size in vivo; Staczek P et al.; In bacteria, DNA supercoil movement is restricted to subchromosomal regions or 'domains.' To elucidate the nature of domain boundaries, we analysed reaction kinetics for gammadelta site-specific resolution in six chromosomal intervals ranging in size from 14 to 90 kb . In stationary cultures of Salmonella typhimurium, resolution kinetics were rapid for both short and long intervals, suggesting that random stationary barriers occur with a 30% probability at approximately 80 kb intervals along DNA . To test the biochemical nature of domain barriers, a genetic screen was used to look for mutants with small domains . Rare temperature-sensitive alleles of DNA gyrase and Topo IV (the two essential type II topoisomerases) had more supercoil barriers than wild-type strains in all growth states . The most severe gyrase mutants were found to have twice as many barriers in growing cells as wild type throughout a 90 kb interval of the chromosome . We propose that knots and tangles in duplex DNA restrain supercoil diffusion in living bacteria. Nippon Rinsho, 1998 Sep, 56(9), 2376 - 81 {Bleeding infectious enteritis}; Mitsuda T et al.; A recent trend on bleeding intestinal infections in Japan was described . Salmonella Enteritidis infection occupied over 42% of food-borne diseases in 1996 . Salmonella Enteritidis is the most popular infectious agent for food-borne outbreak in Japan . Salmonella Typhimurium DT104 which is widely spread in Europe and in U.S.A . is not common in Japan . We experienced large outbreak of foodbore EHEC/VTEC O157: H7 infections in 1996 . Since then, diagnostic and therapeutic studies on EHEC/VTEC infection and haemolytic uremic syndrome are promoted by the Government . HACCP may take an important roll for the prevention of large outbreaks of foodbore EHEC/VTEC infections. Chem Res Toxicol, 1998 Oct, 11(10), 1195 - 200 Identification of a 2-phenylbenzotriazole (PBTA)-type mutagen, PBTA-2, in water from the Nishitakase River in Kyoto; Oguri A et al.; We previously isolated five mutagens, compounds I-V, in blue rayon-adsorbed materials from the Nishitakase River in Kyoto . The chemical structure of compound I, a major mutagen that accounted for 21% of the total mutagenicity, was determined to be 2-{2-(acetylamino)-4-{bis(2-methoxyethyl)amino}-5-methoxyphenyl}-5-am ino-7-bromo-4-chloro-2H-benzotriazole (PBTA-1) . Compound II was also a major mutagen and accounted for 17% of the total mutagenicity . In this study, a large quantity (1.2 mg) of compound II was isolated from adsorbate to 27 kg of blue cotton, and its UV, mass, and 1H NMR spectra were analyzed . On the basis of the spectral data, compound II was deduced to be the PBTA-1 analogue 2-{2-(acetylamino)-4-{N-(2-cyanoethyl)ethylamino}-5-methoxyphenyl}-5- amino-7-bromo-4-chloro-2H-benzotriazole (PBTA-2) . As with PBTA-1, PBTA-2 was synthesized from an azo dye by reduction and chlorination . Since all of the spectra of PBTA-2 coincided with those of compound II obtained from river water, compound II was concluded to be PBTA-2 . PBTA-2 is a newly identified potent mutagen, which induces 93 000 and 3 200 000 revertants of Salmonella typhimurium TA98 and YG1024 per microgram, respectively, in the presence of S9 mix . Like PBTA-1, PBTA-2 may also be produced from an azo dye during industrial processes in dyeing factories and treatment at sewage plants. Chem Res Toxicol, 1998 Oct, 11(10), 1137 - 44 1,3-Dichloropropene epoxides: intermediates in bioactivation of the promutagen 1,3-dichloropropene; Schneider M et al.; 1,3-Dichloropropene (1,3-D), a major soil fumigant nematicide, is genotoxic in many types of assays, leading to its classification as possibly carcinogenic in humans . This study tests in three steps the hypothesis that 1,3-D is a promutagen activated by epoxidation and further reaction of the 1,3-D-epoxides . Stereospecific epoxidation of 1,3-D (examined as the cis/trans mixture and as individual isomers) to the corresponding cis- and trans-1,3-D-epoxides is demonstrated here for the first time, both in vitro in a mouse liver microsome-NADPH system and in vivo in the liver of ip-treated mice, using GC/MS for product identification and quantitation . The cis epoxide is observed in higher yield than the trans epoxide, both in vitro and in vivo, and the cis isomer also reacts slower than the trans isomer with GSH alone or catalyzed by GSH S-transferase . cis- and trans-1,3-D-Epoxides are stable in acetone or chloroform but degrade completely in Me2SO exclusively to 2-chloroacrolein (30 min at 40 degrees C) . Epoxide decomposition is slower in pH 7.4 phosphate buffer (t1/2 = 116 and 64 min for cis and trans, respectively, at 41 degrees C) with a >99% yield of 3-chloro-2-hydroxypropanal (and its dimer) and <0.5% formation of 2-chloroacrolein (for which the t1/2 is 248 min at 41 degrees C) . Mutagenicity assays in Salmonella typhimurium TA100 (standard plate incorporation) establish high potencies of 37, 17, and 150 revertants/nmol for cis- and trans-1, 3-D-epoxides and 2-chloroacrolein, respectively . The mutagenicity of the epoxides is due either to their direct action or to a degradation product formed at physiological pH, i.e., 3-chloro-2-hydroxypropanal or its dehydrochlorination products . The candidate mutagens methylglyoxal and glycidaldehyde are not detected as breakdown products of 3-chloro-2-hydroxypropanal at pH 7.4 and also have low mutagenic activity in TA100 . It is therefore proposed that the penultimate and ultimate mutagens of 1,3-D metabolism are the corresponding epoxides and their direct hydrolysis product 3-chloro-2-hydroxypropanal, respectively. Environ Mol Mutagen, 1998, 32(2), 192 - 6 Selection of agar for use in Salmonella typhimurium and Escherichia coli mutation assays; Majeska JB et al.; The spontaneous and induced revertant frequency of four Salmonella typhimurium strains (TA1535, TA1537, TA98, and TA100) and Escherichia coli {WP2 uvrA (pKM101)} was evaluated using Vogel Bonner minimal plates prepared with ten different agars . In addition to the Difco Bacto agar originally recommended by Ames, Difco Noble, granulated and Bitek agars; BD grade A, BBL granulated and purified agars; Oxoid purified and No . 1 agars; and GIBCO select agar were tested . Several of these agars have been reported as acceptable alternatives for these Salmonella strains, but comparable studies with E . coli have not been done . The bacteria were treated with DMSO or an appropriate positive control in the presence or absence of an Aroclor 1254-induced rat liver activation system . With the exception of Noble agar in the presence of S9, there was little difference among the responses of the Salmonella strains on any of the agars . However, with E . coli the responses include either a reduction or an increase in spontaneous revertants numbers as well as a reduction in absolute and relative induced revertant frequency . Difco Bacto agar appears to be the most consistent agar for use with these strains . As an alternative, only BBL purified agar resulted in consistent results for all of these strains under all testing conditions . These results emphasize the need to evaluate the components of the standard mutation assay when incorporating additional bacterial strains . Suboptimal responses related to the agar or other components could compromise the detection of weak mutagens. Microb Comp Genomics, 1998, 3(3), 151 - 69 The CorA magnesium transporter gene family; Kehres DG et al.; The CorA transport system is the primary Mg2+ influx system of Salmonella typhimurium and Escherichia coli . The CorA protein has no homology to any other known family of proteins . It has an unusual membrane topology, with a large, soluble, highly charged periplasmic N-terminal domain with three transmembrane segments in a shorter, hydrophobic C-terminal domain . Previous phenotypic and molecular data had suggested that this transport system was widespread in the Bacteria . In this report we show that CorA is virtually ubiquitous in the Bacteria and Archaea, forming a distinct family of transport proteins . Genomic sequences to date have revealed at least 22 members of the CorA family in the Bacteria and the Archaea, with 6 more distant members in the yeasts . Only three of the smallest bacterial genomes lack a CorA homologue . Strikingly, phylogenetic analysis does not show clustering by related species or even within kingdom . Several species of Bacteria contain two or even three CorA paralogues . Within species, these paralogues are not closely related, however, and we suggest that they might have distinct transport functions . A multiple alignment suggests three extended consensus regions within the N-terminal soluble domain of CorA, which is predicted to be virtually all alpha-helical . A fourth consensus region includes the last 20 residues of the soluble domain and continues through the entire membrane domain . The first half of this last consensus domain may form an amphipathic alpha-helix that extends from the soluble domain into the first transmembrane segment . The degree of charge in the first transmembrane segment is quite variable, and we suggest that this transport family may include members with only two rather than three transmembrane segments . If so, this would place the N-terminal soluble domain on different sides of the membrane in different members of the family . We suggest that the CorA Mg2+ transport system forms the major Mg2+ uptake system in the Bacteria and Archaea but that some family members may have a function other than Mg2+ transport. Comp Immunol Microbiol Infect Dis, 1998 Oct, 21(4), 327 - 36 Passive immunisation of neonatal lambs via colostrum and milk of ewes previously immunised with live attenuated Salmonella typhimurium protects neonatal lambs from experimental salmonellosis; Mukkur TK et al.; Lambs sucking non-immunised ewes or ewes immunised 4-5 weeks before lambing with live attenuated, aromatic-dependent (aroA) Salmonella typhimurium (strain CS 332) were challenged orally at either 2, 4 or 7 days of age with virulent S . typhimurium (strain CS 94) at doses ranging from 10(9) to 10(13) colony forming units . No lambs displayed signs of clinical salmonellosis and all survived challenge but those sucking immunised ewes had organisms of the challenge strain in their faeces for much shorter periods of time than lambs of the control ewes . High titres of specific antibodies were measured in colostrum and milk of immunised ewes in comparison with very low titres measured in samples from control ewes; these differences were reflected by the titres of antibodies in the sera of corresponding lambs . At 2 days after lambing, the major antibody isotype in the colostrum of immunised ewes and sera of their lambs was IgM whereas at 7 days IgG1 was the predominant isotype . While it was clear that vaccination of pregnant ewes with the live attenuated vaccination conferred protection against experimentally-induced salmonellosis in their lambs, considerable protection was observed in control lambs in spite of there being very low titres of antibodies in the mammary secretion of their dams . The latter observation could be related to the presence of contain non-antibody potent bactericidal factors previously described in colostrum and milk. J Struct Biol, 1998, 122(3), 311 - 9 Architectural features of the Salmonella typhimurium flagellar motor switch revealed by disrupted C-rings; Khan S et al.; The three-dimensional surface topology of rapid-frozen Salmonella typhimurium flagellar hook basal body complexes was studied by stereo-examination of thin-film metal replicas . The complexes contained the extended cytoplasmic structure, composed of the switch complex proteins; FliG, FliM, and FliN . Distinct nanometer-scale element arrays, separated by grooves, defined the outer surface of the cytoplasmic (C-) ring . The number of array elements was comparable to previously determined FliG and FliM copy numbers in the basal body . In addition to basal body complexes lacking C-rings, complexes containing incomplete C-rings were identified . The incomplete C-rings had lost segments of the proximal array . Basal bodies with the distal C-ring array alone were not found . These findings are compatible with the spatial organization of the flagellar switch suggested by previous biochemical data . Presse Med, 1998 May 23-30, 27(19), 909 - 10 {Cerebral abscess during a severe form of Salmonella typhimurium bacteremia in an immunocompetent patient}; Broux C et al.; BACKGROUND: Bacteremia rarely occurs in non-typhoid salmonella infections and the development of a brain abscess is exceptional . CASE REPORT: An immunocompetent patient developed severe Salmonella typhimurium bacteremia leading to septic shock and acute respiratory distress and acute renal failure . A brain abscess, which was not present on the initial brain tomodensitometry, developed and totally regressed after antibiotic therapy . DISCUSSION: We were unable to identify and factor favoring the development of salmonella bacteremia in this patient . There were no cerebral lesions on the initial brain tomodensitometry considered to be normal . To our knowledge, this is the first report of Salmonella typhimurium brain abscess in an immunocompetent subject. Mol Microbiol, 1998 Sep, 29(5), 1191 - 202 Deletion analysis of MotA and MotB, components of the force-generating unit in the flagellar motor of Salmonella; Muramoto K et al.; MotA and MotB are cytoplasmic membrane proteins that form the force-generating unit of the flagellar motor in Salmonella typhimurium and many other bacteria . Many missense mutations in both proteins are known to cause slow motor rotation (slow-motile phenotype) or no rotation at all (non-motile or paralysed phenotype) . However, large stretches of sequence in the cytoplasmic regions of MotA and in the periplasmic region of MotB have failed to yield these types of mutations . In this study, we have investigated the effect of a series of 10-amino-acid deletions in these phenotypically silent regions . In the case of MotA, we found that only the C-terminal 5 amino acids were completely dispensable; an adjacent 10 amino acids were partially dispensable . In the cytoplasmic loop region of MotA, deletions made the protein unstable . For MotB, we found that two large segments of the periplasmic region were dispensable: the results with individual deletions showed that the first consisted of six deletions between the sole transmembrane span and the peptidoglycan binding motif, whereas the second consisted of four deletions at the C-terminus . We also found that deletions in the MotB cytoplasmic region at the N-terminus impaired motility but did not abolish it . Further investigations in MotB were carried out by combining dispensable deletion segments . The most extreme version of MotB that still retained some degree of function lacked a total of 99 amino acids in the periplasmic region, beginning immediately after the transmembrane span . These results indicate that the deleted regions in the MotA cytoplasmic loop region are essential for stability; they may or may not be directly involved in torque generation . Part of the MotA C-terminal cytoplasmic region is not essential for torque generation . MotB can be divided into three regions: an N-terminal region of about 30 amino acids in the cytoplasm, a transmembrane span and about 260 amino acids in the periplasm, including a peptidoglycan binding motif . In the periplasmic region, we suggest that the first of the two dispensable stretches in MotB may comprise part of a linker between the transmembrane span of MotB and its attachment point to the peptidoglycan layer, and that the length or specific sequence of much of that linker sequence is not critical . About 40 residues at the C-terminus are also unimportant. Res Microbiol, 1998 May, 149(5), 309 - 18 Inhibition of Salmonella intracellular proliferation by non-phagocytic eucaryotic cells; Martinez-Moya M et al.; Salmonella typhimurium is an intracellular pathogen capable of proliferating within vacuolar compartments of non-phagocytic eucaryotic cells . This process has been shown to be essential for virulence in the mouse typhoid model (Leung and Finlay, Proc . Natl . Acad . Sci . USA, 88, 11470-11474, 1990) . Here we present evidence that certain non-phagocytic eucaryotic cell lines, such as 3T3 (mouse fibroblasts) and NRK (rat fibroblasts) cells, are not permissive for S . typhimurium intracellular proliferation . Moreover, viability of intracellular bacteria residing within both cell types notably decreases at late postinfection times (72 h) . These results clearly demonstrate that non-phagocytic eucaryotic cells are capable of destroying intracellular S . typhimurium . Experimentation with 3T3 and NRK cell lines might provide an appropriate in vitro model for identifying new bacterial and/or eucaryotic factors regulating Salmonella intracellular proliferation within vacuoles of the host eucaryotic cell. J Food Prot, 1998 Sep, 61(9), 1124 - 8 Antibacterial effects of N-sulfonated and N-sulfobenzoyl chitosan and application to oyster preservation; Chen CS et al.; The antibacterial effects of sulfonated and sulfobenzoyl chitosans were evaluated and compared with that of 69% deacetylated chitosan (DD69 chitosan) . Minimal inhibitory concentrations of sulfonated chitosan (SC1, 0.63% sulfur content) against Shigella dysenteriae, Aeromonas hydrophila, Salmonella typhimurium, and Bacillus cereus were found to be lower than those of DD69 chitosan . A high sulfur content in sulfonated chitosan adversely influenced its antibacterial effect . Sulfobenzoyl chitosan (SBC) has excellent water solubility and an antibacterial effect comparable to that of SC1 . SBC at 1,000 and 2,000 ppm extended the shelf life of oysters at 5 degrees C by 4 days at the former or by 7 days at least at the latter concentration . The growth of coliforms and Pseudomonas, Aeromonas, and Vibrio species on oysters was retarded by the addition of DD69 chitosan or SBC. J Bacteriol, 1998 Oct, 180(20), 5384 - 97 Flk couples flgM translation to flagellar ring assembly in Salmonella typhimurium; Karlinsey JE et al.; The hook-basal body (HBB) is a key intermediate structure in the flagellar assembly pathway in Salmonella typhimurium . The FlgM protein inhibits the flagellum-specific transcription factor sigma28 in the absence of the intact HBB structure and is secreted out of the cell following HBB completion . The flk gene encodes a positive regulator of the activity of FlgM at an assembly step just prior to HBB completion: at the point of assembly of the P- and L-rings . FlgM inhibition of sigma28-dependent class 3 flagellar gene transcription was relieved in P- and L-ring assembly mutants (flgA, flgH, and flgI) by introduction of a null mutation in the flk gene (J . E . Karlinsey et al., J . Bacteriol . 179:2389-2400, 1997) . In P- and L-ring mutant strains, recessive mutations in flk resulted in a reduction in intracellular FlgM levels to those seen in wild-type (Fla+) strains . The reduction in intracellular FlgM levels by mutations in the flk gene was concomitant with a 10-fold increase in transcription of the flgMN operon compared to that of the isogenic flk+ strain, while transcription of the flgAMN operon was unaffected . This was true for both direct measurement of the flgAMN and flgMN mRNA transcripts by RNase T2 protection assays and for lac operon fusions to either the flgAMN or flgMN promoter . Loss of Flk did not allow secretion of FlgM through basal-body structures lacking the P- and L-rings . Intracellular FlgM was stable to proteolysis, and turnover occurred primarily after export out of the cell . Loss of Flk did not result in increased FlgM turnover in either P- or L-ring mutant strains . With lacZ translational fusions to flgM, a null mutation in flk resulted in a significant reduction of flgM-lacZ mRNA translation, expressed from the class 3 flgMN promoter, in P- and L-ring mutant strains . No reduction in either flgAMN or flgMN mRNA stability was measured in the absence of Flk in Fla+, ring mutant, or HBB deletion strains . We conclude that the reduction in the intracellular FlgM levels by mutation in the flk gene is only at the level of flgM mRNA translation. J Bacteriol, 1998 Oct, 180(20), 5299 - 305 Domain structure of the ATP-binding-cassette protein MalK of salmonella typhimurium as assessed by coexpressed half molecules and LacK'-'MalK chimeras; Schmees G et al.; ATP-binding-cassette (ABC) subunit MalK of the binding protein-dependent transport system for maltose of Salmonella typhimurium and Escherichia coli is crucial to the transport process but also exhibits a repressing activity on other genes of the maltose regulon . The latter function has been attributed to a carboxy-terminal extension by which MalK differs in length from a prototype ABC protein . In order to define the boundaries of putative functional domains of MalK, we have analyzed pairs of N- and C-terminally truncated MalK proteins of S . typhimurium . Coexpressed half molecules of about equal lengths (MalKN1: residues 1 to 179; MalKC1: residues 179 to 369) restored the transport activity of a malK strain and displayed substantial regulatory activity . The same regulatory activity was obtained when malKC1 was expressed separately . These results indicate that a covalent linkage is not absolutely essential for function and that the protein might be composed of two structurally distinct entities . To elucidate further the minimal structural requirements for the regulatory function of MalK, we have studied chimeric proteins that have C-terminal portions of MalK fused to the corresponding amino-terminal fragments of its close homolog LacK . Functional analyses revealed that a fusion containing only the C-terminal extension of MalK (Q263 to V369) is sufficient to display half-maximal regulatory activity . This activity increased with the lengths of the MalK portions present in the chimeras . Furthermore, the failure of two chimeras to support maltose transport suggests a structurally critical region between residues 243 and 264 . In the absence of a crystal structure, this work contributes to the understanding of the multiple functions of MalK. Genes Dev, 1998 Oct 1, 12(19), 3123 - 36 The flagellar anti-sigma factor FlgM actively dissociates Salmonella typhimurium sigma28 RNA polymerase holoenzyme; Chadsey MS et al.; The anti-sigma factor FlgM of Salmonella typhimurium inhibits transcription of class 3 flagellar genes through a direct interaction with the flagellar-specific sigma factor, sigma28 . FlgM is believed to prevent RNA polymerase (RNAP) holoenzyme formation by sequestering free sigma28 . We have analyzed FlgM-mediated inhibition of sigma28 activity in vitro . FlgM is able to inhibit sigma28 activity even when sigma28 is first allowed to associate with core RNAP . Surface plasmon resonance (SPR) was used to evaluate the interaction between FlgM and both sigma28 and sigma28 holoenzyme (Esigma28) . The Kd of the sigma28-FlgM complex is approximately 2 x 10(-10) M; missense mutations in FlgM that cause a defect in sigma28 inhibition in vivo increase the Kd of this interaction by 4- to 10-fold . SPR measurements of Esigma28 dissociation in the presence of FlgM indicate that FlgM destabilizes Esigma28, presumably via an interaction with the sigma subunit . Our data provide the first direct evidence of an interaction between FlgM and Esigma28 . We propose that this secondary activity of FlgM, which we term holoenzyme destabilization, enhances the sensitivity of the cell to changes in FlgM levels during flagellar biogenesis. Arch Toxicol, 1998 Jul-Aug, 72(8), 505 - 13 Correlation of 32P-postlabelling-detection of DNA adducts in mouse skin in vivo with the polycyclic aromatic compound content and mutagenicity in Salmonella typhimurium of a range of oil products; Booth ED et al.; The in vivo genotoxic activities in mouse skin of the dimethyl sulphoxide (DMSO) extracts of a range of oil products {residual aromatic extract; untreated heavy paraffinic distillate aromatic extract; mildly refined light naphthenic base oil; bitumen (vacuum residue); high viscosity index base oil obtained by catalytic hydrogenation} were evaluated by 32P-postlabelling DNA analysis . The results of quantitative 32P-postlabelling analyses of epidermal DNA from mice treated with the DMSO extracts showed linear relationships with the total polycyclic aromatic compound (PAC) contents, determined by the Institute of Petroleum method IP 346 and also the 3-6 ring PAC contents, measured by on-line liquid-liquid extraction using flow injection analysis . The 32P-postlabelling data also showed a linear relationship with the mutagenicity indices of these oil products determined in S . typhimurium TA98 using the modified Ames Salmonella microsome test . The in vivo genotoxicity of the DMSO extracts from the oil products was low, judged by 32P-postlabelling analysis of DNA adducts measured in epidermal DNA of treated mouse skin, and ranging from 2 to 723 attomole/microg DNA per mg oil product . The in vivo 32P-postlabelling data from this study are consistent with these materials expressing low genotoxicity in mouse skin in vivo . The DMSO extraction procedure coupled with 32P-postlabelling DNA analysis is useful for ranking the relative genotoxic potency in vivo of a wide range of oil products . In general the trend observed is similar to rankings based on physicochemical measurements of total PAC contents or 3 6 ring PAC contents of the oil products. Anal Biochem, 1978 Nov, 91(1), 46 - 59 Improved radioisotopic assay for cytidine 5'-triphosphate synthetase (EC 6.3.4.2); Williams JC et al.; An improved radioassay for cytidine 5-triphosphate synthetase is reported which employs thin-layer chromatographic methods and provides a number of advantages over previously available techniques . (i) The method resolves the nucleotides and the degradation products generated during the time course of the enzymatic reaction by ascending chromatography employing polyethyleneimine cellulose plastic-backed sheets . (ii) Determinations of CTP formed and all nucleotide pairs generated during kinetic analysis of CTP synthetase are greatly simplified, further facilitating the detection of extraneous enzymatic activities . (iii) The sensitivity of the assay is enhanced and as little as 50 pmol of product formed was readily detected in supernatant fluids . This was made possible, in part, by the addition of NaF and phosphoenolpyruvate which together maintain the nucleotide triphosphates in the reaction mixture . (iv) A large number of samples can be handled at one time with highly reproducible results . The synthesis of CTP from UTP by enzyme preparations from rat liver, hepatomas, and Salmonella typhimurium LT2 was quantitated with this method. J Mol Biol, 1998, 283(1), 121 - 33 Three-dimensional structure of O-acetylserine sulfhydrylase from Salmonella typhimurium; Burkhard P et al.; The last step in cysteine biosynthesis in enteric bacteria is catalyzed by the pyridoxal 5'-phosphate-dependent enzyme O-acetylserine sulfhydrylase . Here we report the crystal structure at 2.2 A resolution of the A-isozyme of O-acetylserine sulfhydrylase isolated from Salmonella typhimurium . O-acetylserine sulfhydrylase shares the same fold with tryptophan synthase-beta from Salmonella typhimurium but the sequence identity level is below 20% . There are some major structural differences: the loops providing the interface to the alpha-subunit in tryptophan synthase-beta and two surface helices of tryptophan synthase-beta are missing in O-acetylserine sulfhydrylase . The hydrophobic channel for indole transport from the alpha to the beta active site of tryptophan synthase-beta is, not unexpectedly, also absent in O-acetylserine sulfhydrylase . The dimer interface, on the other hand, is more or less conserved in the two enzymes . The active site cleft of O-acetylserine sulfhydrylase is wider and therefore more exposed to the solvent . A possible binding site for the substrate O-acetylserine is discussed . Antimicrob Agents Chemother, 1998 Oct, 42(10), 2511 - 20 Intracellular delivery and antibacterial activity of gentamicin encapsulated in pH-sensitive liposomes; Lutwyche P et al.; Cell membranes are relatively impermeable to the antibiotic gentamicin, a factor that, along with the toxicity of gentamicin, precludes its use against many important intracellular bacterial infections . Liposomal encapsulation of this drug was used in order to achieve intracellular antibiotic delivery and therefore increase the drug's therapeutic activity against intracellular pathogens . Gentamicin encapsulation in several dipalmitoylphosphatidylcholine (DPPC) and pH-sensitive dioleoylphosphatidylethanolamine (DOPE)-based carrier systems was characterized . To systematically test the antibacterial efficacies of these formulations, a tissue culture assay system was developed wherein murine macrophage-like J774A.1 cells were infected with bacteria and were then treated with encapsulated drug . Of these formulations, DOPE-N-succinyl-DOPE and DOPE-N-glutaryl-DOPE (70:30;mol:mol) containing small amounts of polyethyleneglycol-ceramide showed appreciable antibacterial activities, killing greater than 75% of intracellular vacuole-resident wild-type Salmonella typhimurium compared to the level of killing of the control formulations . These formulations also efficiently eliminated intracellular infections caused by a recombinant hemolysin-expressing S . typhimurium strain and a Listeria monocytogenes strain, both of which escape the vacuole and reside in the cytoplasm . Control non-pH-sensitive liposomal formulations of gentamicin had poor antibacterial activities . A fluorescence resonance energy transfer assay indicated that the efficacious formulations undergo a pH-dependent lipid mixing and fusion event . Intracellular delivery of the fluorescent molecules encapsulated in these formulations was confirmed by confocal fluorescence microscopy and was shown to be dependent on endosomal acidification . This work shows that encapsulation of membrane-impermeative antibiotics in appropriately designed lipid-based delivery systems can enable their use in treating intracellular infections and details the development of a general assay for testing the intracellular delivery of encapsulated drug formulations. Genetics, 1998 Oct, 150(2), 533 - 42 Mechanism and control of interspecies recombination in Escherichia coli . I . Mismatch repair, methylation, recombination and replication functions; Stambuk S et al.; A genetic analysis of interspecies recombination in Escherichia coli between the linear Hfr DNA from Salmonella typhimurium and the circular recipient chromosome reveals some fundamental aspects of recombination between related DNA sequences . The MutS and MutL mismatch binding proteins edit (prevent) homeologous recombination between these 16% diverged genomes by at least two distinct mechanisms . One is MutH independent and presumably acts by aborting the initiated recombination through the UvrD helicase activity . The RecBCD nuclease might contribute to this editing step, presumably by preventing reiterated initiations of recombination at a given locus . The other editing mechanism is MutH dependent, requires unmethylated GATC sequences, and probably corresponds to an incomplete long-patch mismatch repair process that does not depend on UvrD helicase activity . Insignificant effects of the Dam methylation of parental DNAs suggest that unmethylated GATC sequences involved in the MutH-dependent editing are newly synthesized in the course of recombination . This hypothetical, recombination-associated DNA synthesis involves PriA and RecF functions, which, therefore, determine the extent of MutH effect on interspecies recombination . Sequence divergence of recombining DNAs appears to limit the frequency, length, and stability of early heteroduplex intermediates, which can be stabilized, and the recombinants mature via the initiation of DNA replication. Eur J Immunol, 1998 Sep, 28(9), 2913 - 20 Innate resistance to infection by intracellular bacterial pathogens differs in mice selected for maximal or minimal acute inflammatory response; Araujo LM et al.; The intensity of nonspecific immune reaction and the host resistance to facultative intracellular pathogens are found to be associated in lines of mice selected for maximal (AIRmax) or minimal (AIRmin) acute inflammatory reactivity . AIRmax are more resistant than AIRmin mice to Salmonella typhimurium and Listeria monocytogenes infection, the differences between lines in LD50 being > 1000 and 100 times, respectively . This difference was shown to be related to the initial bacterial containment at the infectious focus, and to the control of bacterial multiplication in the spleen during the 1st week after s . c . inoculation of the bacteria . Specific immune responses were not deeply affected by the selective process: antibody production and delayed-type hypersensitivity were both of similar intensity in AIRmax and AIRmin mice . The differential susceptibility to infection seems independent of the Nramp-1 locus polymorphism; therefore, these two lines represent a powerful model for investigating the role of other genetic loci regulating the nonspecific immunity effectors in the course of infectious diseases. Can Vet J, 1998 Sep, 39(9), 559 - 65 Salmonella typhimurium DT104: a virulent and drug-resistant pathogen; Poppe C et al.; Salmonella typhimurium phage type (PT) or definitive type (DT) 104 is a virulent pathogen for humans and animals, particularly cattle . It has been isolated increasingly from humans and animals in the United Kingdom and several other European countries and, more recently, in the United States and Canada . Humans may acquire the infection from foods of animal origin contaminated with the infective organism . Farm families are particularly at risk of acquiring the infection by contact with infected animals or by drinking unpasteurized milk . The symptoms in cattle are watery to bloody diarrhea, a drop in milk production, pyrexia, anorexia, dehydration and depression . Infection may result in septicemic salmonellosis and, upon necropsy, a fibrinonecrotic enterocolitis may be observed . The infection occurs more commonly in the calving season than at other times . Feedlot cattle and pigs may also be affected . Prolonged carriage and shedding of the pathogen may occur . Symptoms in humans consist of diarrhea, fever, headache, nausea, abdominal pain, vomiting, and, less frequently, blood in the stool . Salmonella typhimurium DT104 strains are commonly resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, and tetracycline. Yi Chuan Xue Bao, 1998 Apr, 25(2), 181 - 7 {Expression regulation of purine biosynthetic genes in Salmonella typhimurium . VI . Isolation and characterization of super-repressor mutants}; Tang H et al.; Starting from strain of Salmonella typhimurium purD::lac, 86 exponential cultures were mutagenized with NTG and white or light blue clones on E + ado + Xgal plate were selected as candidates of purRs mutant . Total 66 independent candidate strains were obtained . By assaying their beta-galactosidase activity under the repressed and derepressed conditions, determining their frequency of revertional mutation, Conducting transductional analysis of mutational site and dorminance test, 11 candidates strains were proved to be super-repressor mutants . These mutants are useful for studying the expression of purine biosynthetic gene and relationship between protein structure and function in general. J Bacteriol, 1998 Oct, 180(19), 5231 - 4 Cell division inhibition in Salmonella typhimurium histidine-constitutive strains: an ftsI-like defect in the presence of wild-type penicillin-binding protein 3 levels; Cano DA et al.; Histidine-constitutive (Hisc) strains of Salmonella typhimurium undergo cell division inhibition in the presence of high concentrations of a metabolizable carbon source . Filaments formed by Hisc strains show constrictions and contain evenly spaced nucleoids, suggesting a defect in septum formation . Inhibitors of penicillin-binding protein 3 (PBP3) induce a filamentation pattern identical to that of Hisc strains . However, the Hisc septation defect is caused neither by reduced PBP3 synthesis nor by reduced PBP3 activity . Gross modifications of peptidoglycan composition are also ruled out . D-Cycloserine, an inhibitor of the soluble pathway producing peptidoglycan precursors, causes phenotypic suppression of filamentation, suggesting that the septation defect of Hisc strains may be caused by scarcity of PBP3 substrate. Biochemistry, 1998 Sep 22, 37(38), 13359 - 69 Structure of Salmonella typhimurium nrdF ribonucleotide reductase in its oxidized and reduced forms; Eriksson M et al.; The first class Ib ribonucleotide reductase R2 structure, from Salmonella typhimurium, has been determined at 2.0 A resolution . The overall structure is similar to the Escherichia coli class Ia enzyme despite only 23% sequence identity . The most spectacular difference is the absence of the pleated sheet and adjacent parts present in the E . coli R2 structure; the heart-shaped structure loses its tip . From sequence comparisons, it appears that this feature is shared with all other class Ib enzymes and, in this respect, is more like the mammalian class Ia enzymes . Both the oxidized and reduced iron forms have been investigated . In the ferric iron center, both iron ions are octahedrally coordinated and bridged by one carboxylate and one oxide ion . The ferrous form has lost the bridging oxide ion but is bridged by two carboxylates . Accompanying the change in redox state, helix E changes its conformation from one covering the metal center in the oxidized form to a more open reduced form . A narrow channel is opened which may permit easier access of oxygen to the ferrous iron site and to efficiently generate the tyrosyl radical. J Biol Chem, 1998 Oct 2, 273(40), 25745 - 50 The glucose transporter of Escherichia coli with circularly permuted domains is active in vivo and in vitro; Gutknecht R et al.; The bacterial phosphotransferase system (PTS) consists of two energy-coupling soluble proteins (enzyme I and HPr) and a large number of inner membrane transporters (enzymes II) that mediate concomitant phosphorylation and translocation of sugars and hexitols . The transporters consist of three functional units (IIA, IIB, IIC), which occur either as protein subunits or domains of a multidomain polypeptide . The membrane-spanning IIC domain contains the substrate binding site; IIA and IIB are phosphorylation domains that transfer phosphate from HPr to the transported sugar . The transporter complexes of the PTS are good examples for variation of design by modular assembly of domains and subunits . The domain order is IIC-IIB in the membrane subunit of the Escherichia coli glucose transporter (IICBGlc) and IIB-IIC in Salmonella typhimurium sucrose transporter (IIBCScr) . The phosphorylation domain of IICBGlc was translocated from the carboxyl-terminal to the amino-terminal end of the IIC domain, and the activity of the circularly permuted form was optimized by variation of the length and the composition of the interdomain linker . IIBapCGlc with an alanine-proline-rich interdomain linker has 70% of the control specific activity after purification and reconstitution into proteoliposomes . These results indicate that the amino-terminal end of IICBGlc must be on the cytoplasmic side of the inner membrane, that membrane insertion of the IIC domain is insensitive to the modification of its amino-terminal end, and that a domain swap as it could occur by a single DNA translocation event can rapidly lead to a functional protein . However, IIB could not be substituted for by glucokinase . Fusion proteins between the IIC domain and glucokinase do not transport and phosphorylate glucose in an ATP-dependent mechanism, although the IIC moiety displays transport activity upon complementation with soluble subclonal IIB, and the glucokinase moiety retains ATP-dependent nonvectorial kinase activity . This indicates that IIC and IIB are two cooperative units and not only sequentially acting upon a common substrate, and that translocation of glucose must be conformationally coupled to the phosphorylation/dephosphorylation cycle of IIB. Vet Rec, 1998 Aug 8, 143(6), 155 - 8 Causes of death of wild birds of the family Fringillidae in Britain; Pennycott TW et al.; The provision of supplementary food for wild birds in gardens during the winter months is common in the UK, but it is possible that it may precipitate infectious diseases in the birds . This paper describes the results of postmortem examinations of 116 wild finches carried out over a period of four years . The two commonest causes of death in areas where high mortality had been reported were infections with the bacteria Salmonella typhimurium DT40 and Escherichia coli O86 . Coccidia of the genera Atoxoplasma or Isospora were found in several of the birds but were considered to be incidental . Megabacteria were also identified in some of the birds, for the first time in flocks of wild birds in the UK, but they were not considered to be significant. Infect Immun, 1998 Oct, 66(10), 4624 - 32 Invasion by Salmonella typhimurium induces increased expression of the LMP, MECL, and PA28 proteasome genes and changes in the peptide repertoire of HLA-B27; Maksymowych WP et al.; We have analyzed proteasomal adaptation and associated changes in the B27-bound peptide repertoire in response to cellular invasion with Salmonella . The peptide repertoire of HLA-B27 complexes was analyzed by two different methods: (i) high-pressure liquid chromatography (HPLC) profiles of newly synthesized peptides eluted from B27 following metabolic labeling with arginine and (ii) reactivities with two B27 monoclonal antibodies, Ye-2 and B27.M2, sensitive to peptide-induced conformational changes . LMP, MECL, and PA28 expression was analyzed by reverse transcription-PCR (RT-PCR) of mRNA and by Western blot analysis for LMP2 . Invasion of HLA-B27-transfected HeLa cells by Salmonella typhimurium induced significant changes in the reactivities of HLA-B27 with these two antibodies, which was accompanied by significant quantitative and qualitative changes in the HPLC profile of peptides eluted from HLA-B27 . We also observed increases in the RT-PCR values for the LMP2, LMP7, and MECL proteasome subunit genes, as well as the proteasomal activator PA28alpha and -beta genes, and increased expression of the LMP2 protein by Western blotting . Upregulation of LMP2, but not LMP7, gene expression showed a close correlation with the changes in antibody reactivities observed upon bacterial invasion . We observed similar changes in reactivity with the Ye-2 or the B27.M2 antibody of lymphoblastoid cells upon gamma interferon treatment, which significantly correlated with the increased RT-PCR values for the LMP2 gene . This was accompanied by consistent HPLC profile changes for eluted peptides . Thus, Salmonella invasion leads to serologically recognizable changes in the B27-bound peptide repertoire, which may include peptides of host origin potentially through modulation of proteasome LMP2 subunit expression and, as a consequence, proteasomal activities. Roum Arch Microbiol Immunol, 1997 Jul-Dec, 56(3-4), 127 - 38 Plasmid profile analysis and antibiotic resistance of Salmonella strains from clinical isolates in Cluj-Napoca; Fagarasan S et al.; Resistance patterns, plasmid profiles and the genetic resistance determinants were investigated in 38 isolates of Salmonella enterica serotype Typhimurium and 19 isolates of Salmonella enterica serovar Enteritidis derived from children hospitalized in two clinics in Cluj-Napoca, during the period of 1995-1997 . Incidence of plasmid and antibiotic resistance was very high in Salmonella typhimurium isolates . All strains were resistant to almost all antibiotics tested but susceptible to the third generation cephalosporines and fluoroquinolones . We identified three resistance patterns and six plasmid profiles . Each plasmid profile was characterized by the presence of two large plasmids of 150-180 Kbp . Approximately 60% of strains harbored three or four small plasmids of 1.3 to 9.5 Kbp . The plasmids of 8.5 Kbp encoded resistance to beta-lactam antibiotics and were non-conjugative . The other small plasmids were cryptic and also non-conjugative . Salmonella enteritidis isolates were susceptible to many antibiotics, except Tetracycline and Trimethoprim-Sulfamethoxazole . We identified three different resistance patterns but nine plasmid profiles . All plasmid profiles were characterized by the presence of a large plasmid (> 100 Kbp) . The number and the diversity of small plasmids were higher than in S . typhimurium strains . There was no parallelism between resistance and plasmid profile: for the same resistance pattern a number of two or three plasmid profiles were found . Our conclusions are that Salmonella typhimurium strains were multiresistant to antibiotics and that many genetically different strains of Salmonella typhimurium and Salmonella enteritidis were responsible for gastroenteritis in children from Cluj County . The increasing antibiotic resistance highlights the need for more refined methods in genetic and epidemiological characterization of bacteria involved in gastrointestinal infections. Aust N Z J Public Health, 1998 Apr, 22(2), 243 - 6 A salmonellosis outbreak linked to internally contaminated pork meat; Delpech V et al.; In August 1995, we investigated an outbreak of salmonellosis among patrons who attended a church camp in southern Sydney . Of the 73 attendees interviewed, 22 reported a gastroenteritis illness within two days of the conclusion of the camp, with one attendee hospitalised . Two stool specimens, one from each of two attendees, were both positive for Salmonella typhimurium phage type 9 . A cohort study of 68 attendees established a statistically significant association between illness and the consumption of de-boned roast pork (estimated relative risk infinite, p = 0.03) and between illness and the degree of cooking of the pork meat (chi 2 for trend 5.8, p < 0.02) . The outbreak was most likely caused by consumption of roast pork that had been internally contaminated during the de-boning process . Meat and meat products that may be internally contaminated, such as de-boned meats, should be thoroughly cooked . Guidelines about minimum cooking temperatures of meats liable to internal contamination should be developed for commercial food handlers in Australia. J Mol Biol, 1998 Oct 2, 282(4), 721 - 30 Regulation of UmuD cleavage: role of the amino-terminal tail; McDonald JP et al.; An essential step in SOS mutagenesis is the RecA-mediated posttranslational processing of UmuD-like proteins to the shorter, but mutagenically active, UmuD'-like proteins . Interestingly, the UmuD-like proteins undergo posttranslational processing at different rates . For example, although the Escherichia coli UmuD (UmuDEc) and the Salmonella typhimurium UmuD (UmuDSt) proteins are 73% identical, UmuDSt is processed in vivo at a significantly faster rate than the UmuDEc protein . Here, we report experiments aimed at investigating the molecular basis of these phenotypic differences . The faster rate of UmuDSt cleavage probably does not result solely from a better interaction with RecA, since we observed that, in vitro, UmuDSt undergoes RecA-independent autocatalytic processing about four-times faster than UmuDEc . By constructing chimeric UmuD proteins, we determined that the amino-terminal tail of the UmuD proteins proximal to the Cys24-Gly25 cleavage site is mainly responsible for the difference in UmuDSt and UmuDEc cleavage rates . Site-directed mutagenesis of the UmuDEc protein suggests that most of the enhanced cleavage observed with the UmuDSt protein can be attributed to the presence of a Pro23 residue, juxtaposed to the cleavage site in UmuDSt . Furthermore, this proline residue appears to result in a UmuD protein that is a much better substrate for intermolecular cleavage . These findings clearly implicate the N-terminal tail of the UmuD-like proteins as playing an important and unexpected regulatory function in the maturation of the mutagenically active UmuD'-like mutagenesis proteins . FEMS Microbiol Lett, 1998 Aug 15, 165(2), 289 - 93 Two novel plasmid-mediated cefotaxime-hydrolyzing beta-lactamases (CTX-M-5 and CTX-M-6) from Salmonella typhimurium; Gazouli M et al.; Two novel plasmid-mediated beta-lactamases (CTX-M-5 and CTX-M-6) produced by Salmonella typhimurium clinical strains were characterized . The enzymes exhibited a pI of 8.4, hydrolyzed oxyimino-beta-lactams and were susceptible to mechanism-based beta-lactamase inhibitors . The respective bla genes were cloned and sequenced . The deduced amino acid sequences showed a high degree of homology with those of the previously described plasmid class A CTX-M-type enzymes and appeared related to the chromosomal beta-lactamases of Klebsiella oxytoca. Biochem J, 1998 Oct 1, 335 ( Pt 1), 167 - 73 Cobalamin (vitamin B12) biosynthesis: functional characterization of the Bacillus megaterium cbi genes required to convert uroporphyrinogen III into cobyrinic acid a,c-diamide; Raux E et al.; The function of individual genes of the Bacillus megaterium cobI operon genes in cobalamin (vitamin B12) biosynthesis was investigated by their ability to complement defined Salmonella typhimurium cob mutants . This strategy confirmed the role of cbiA, -D, -F, -J, -L and cysGA . Furthermore the operon as a whole was used to restore corrin biosynthesis in Escherichia coli, which, although closely related to S . typhimurium, does not possess the CobI pathway . When the B . megaterium cob operon was cloned into a plasmid and transformed into an E . coli strain containing the S . typhimurium cbiP, it conferred upon the host strain the ability to make the cobyric acid de novo . However, cobyric acid synthesis was observed only when the strain was grown anaerobically . Derivatives of the corrin-producing E . coli strain were constructed in which genes of the B . megaterium cob operon had been inactivated . These strains were used to demonstrate that, whereas B . megaterium cbiD, -G and -X are essential for cobyric acid synthesis, the cbiW and -Y genes could be deleted without detriment to cobyric acid production in E . coli. Int J Exp Pathol, 1998 Jun, 79(3), 183 - 92 Comparative histopathology in mouse typhoid among genetically diverse mice; Moncure CW et al.; Genetically resistant CBA and A/J mice and susceptible BALB/c and C57BL/6 mice were challenged with either an identical infective dose or a minimal lethal dose of Salmonella typhimurium . The histopathological progression of the disease was examined in tissue sections prepared by the JB-4 Plus resin embedding method and compared between the resistant and susceptible mice . In a fatal disease, the lesions in both animal hosts began with focal abscesses within the first three days post infection . Mononuclear cell infiltration started by day 4 and transformed the lesions into granulomata . Well-formed granulomata were evident by day 7 and persisted in sublethally infected resistant mice . Massive bacterial proliferation and extensive tissue degeneration marked the terminal stage of a lethal challenge . There were no distinguishable features that would identify the tissue response to infection in a resistant host from a susceptible one, except that the lesions in the sublethally infected resistant mice advanced slower and were discrete and self-limiting. Mol Gen Genet, 1998 Jul, 259(1), 46 - 53 The sfiX, rfe and metN genes of Salmonella typhimurium and their involvement in the His(c) pleiotropic response; Mouslim C et al.; Two loci involved in the pleiotropic response of His(c) strains of Salmonella typhimurium (sfiX and sfiY) have been characterized at the molecular level . The sfiX gene (CS 44) has been identified as a homolog of the E . coli gene sanA, located downstream of the cytidine deaminase gene (cdd) . The cdd-sanA (or cdd-sfiX) operon shows a highly conserved structure in E . coli and Salmonella . Like its E . coli homolog, the sfiX gene of S . typhimurium is required for vancomycin resistance at high temperature . The dual effect of sfiX mutations (induction of vancomycin sensitivity and suppression of cell division inhibition) suggests a link between SfiX function and murein synthesis . The sfiY locus (CS 85), contains two genes arranged in a single transcriptional unit . The upstream gene is a homolog of the E . coli gene rfe; mutations in this gene suppress the cell division defect of His(c) strains . The suppressor effect of rfe mutations can be reproduced by tunicamycin, suggesting that suppression of filamentation results from an increase in the intracellular concentration of UDP-N-acetyl-D-glucosamine . The gene located downstream of rfe is also found in E . coli but its function is unknown . Insertions in rfe suppress the methionine requirement of His(c) strains of S . typhimurium by a polar effect on the downstream gene, tentatively designated metN . Complementation with a rfe+ clone indicates that the rfe gene is not involved in the methionine requirement of His(c) strains . Thus metN expression appears to cause methionine auxotrophy in a His(c) background. J Biol Chem, 1998 Sep 25, 273(39), 25006 - 14 Detection of a conserved alpha-helix in the kinase-docking region of the aspartate receptor by cysteine and disulfide scanning; Bass RB et al.; The transmembrane aspartate receptor of Escherichia coli and Salmonella typhimurium propagates extracellular signals to the cytoplasm, where its cytoplasmic domain regulates the histidine kinase, CheA . Different signaling states of the cytoplasmic domain modulate the kinase autophosphorylation rate over at least a 100-fold range . Biochemical and genetic studies have implicated a specific region of the cytoplasmic domain, termed the signaling subdomain, as the region that transmits regulation from the receptor to the kinase . Here cysteine and disulfide scanning are applied to the N-terminal half of the signaling subdomain to probe its secondary structure, solvent exposure, and protein-protein interactions . The chemical reactivities of the scanned cysteines exhibit the characteristic periodicity of an alpha-helix with distinct solvent-exposed and buried faces . This helix, termed alpha7, ranges approximately from residue 355 through 386 . Activity measurements probing the effects of cysteine substitutions in vivo and in vitro reveal that both faces of helix alpha7 are critical for kinase activation, while the buried face is especially critical for kinase down-regulation . Disulfide scanning of the region suggests that helix alpha7 is not in direct contact with its symmetric partner (alpha7') from the other subunit; presently, the structural element that packs against the buried face of the helix remains unidentified . Finally, a novel approach termed "protein interactions by cysteine modification" indicates that the exposed C-terminal face of helix alpha7 provides an essential docking site for the kinase CheA or for the coupling protein CheW. Food Chem Toxicol, 1998 Sep-Oct, 36(9-10), 811 - 7 Mutagenicity and DNA-damaging activity of decomposed products of food colours under UV irradiation; Ozaki A et al.; Five synthetic food colours Food Red Nos 3, 40 and 102 and Food Blue Nos 1 and 2, and their UV irradiated products were tested for mutagenic activity by means of the Ames test using Salmonella typhimurium strains TA98 and TA100 . Food colours were irradiated with UV light for 14 days . Food Red Nos 3, 40 and 102 and Food Blue No . 1 were non-mutagenic before and after irradiation . UV irradiated products of Food Blue No . 2 were mutagenic in TA98 with or without S-9 mix . The mutagenic activity increased with increasing irradiation period, reached maximum potency on day 6, and then decreased . Moreover, Food Blue No . 2 showed DNA-damaging activity after 14 days of irradiation in rec-assay using Bacillus subtilis strains H17 and M45 . The capillary electrophoresis was applied for the analysis of UV irradiated products of Food Blue No . 2 . The original peak of Food Blue No . 2 was decomposed into seven peaks after UV irradiation. Biochem Biophys Res Commun, 1998 Sep 8, 250(1), 150 - 3 In vivo detection of mutations induced by aflatoxin B1 using human CYP3A7/HITEC hybrid mice; Yamada A et al.; CYP3A7-M10 mouse is a transgenic mouse carrying human CYP3A7 cDNA, in which CYP3A7 is expressed in the small intestine but not in the kidney . HITEC mouse is a transgenic mouse developed to detect mutagenic potency of various chemicals in vivo . The M10/HITEC mouse was established by crossmating of these two strains of mice . When a 9,000 x g supernatant fraction prepared from the small intestine was added to an incubation mixture for Ames test with Salmonella typhimurium TA98 strain to examine the mutagen-producing activity from aflatoxin B1 (AFB1), the mutagen-producing activities of the 9, 000 x g supernatant fraction from the small intestine was found to be 1.7-fold higher in the M10/HITEC mice than in HITEC mice . Such a difference in the capacity to activate AFB1 was not seen with the 9, 000 x g supernatant fraction from the kidney from both strains of mice . Male M10/HITEC mice of 8 weeks old were treated with a single i.p . injection of AFB1 ( 8 mg/kg body weight) . The mutation of the introduced rpsL gene in the genomic DNA from the small intestine and the kidney was analyzed . The mutation frequency in the small intestine of M10/HITEC mice was significantly higher (p<0.05) than that of HITEC mice, while the mutation frequency in both strains was similar in the kidney . These results provide the first evidence for the toxicological function of CYP3A7 in vivo . Mutat Res, 1998 Sep 11, 417(2-3), 141 - 53 Evaluation of the mutagenicity and antimutagenicity of forty-two 3-substituted flavones in the Ames test; Beudot C et al.; The mutagenic and antimutagenic activities of forty-two synthetic flavones were assessed by the Ames test . The tested flavones included twenty-three 3-nitroflavones, eighteen 3-aminoflavones and the 3-chloroflavone . The mutagenicity was evaluated with Salmonella typhimurium TA100 and YG1042 (an overproducing nitroreductase and O-acetyltransferase TA100 strain) with and without metabolic activation (S9 mix) . The antimutagenicity of the non mutagenic derivatives was evaluated against 11 known reference mutagens . A total of 39 synthetic flavones were mutagenic . The mutagenic activities ranged from 0.1 rev/nmole (4'-chloro-6-methoxy-3-nitroflavone) to 6240 rev/nmole (4'-methoxy-3, 3'-diaminoflavone) . Two differences were found between the 3-amino and the 3-nitroflavones: (i) the mutagenicity of the 3-aminoflavones required the presence of the metabolic activation; (ii) the 3-amino derivatives were more mutagenic than their 3-nitro counterparts . Increased mutagenicity, as assessed with strain YG1042, was limited to 17/39 derivatives . The mutagenic activity was induced by the presence of the double bond at the 2,3-position for conjugation of the lone-pair electron with the carbonyl group on the 'C' ring . This mutagenicity was modulated by substituents at the 2'-position . Additional mutagenicity was brought by the aminoaromatic and nitroaromatic group reduction by bacterial nitroreductases and by the S9 mix; it was modulated by different substituents on the aromatic rings of the flavones . Three flavones: 3-chloroflavone (1C), 4'-hydroxy-3-nitroflavone (23N) and 2',3-diaminoflavone (2A) showed antimutagenic properties . Compound 1C was efficient against benzo(a)pyrene (BaP), 2-aminofluorene (2AF), 2-aminoanthracene (2AA), 4-nitroquinoline-1-oxide (4NQO) and 1-methyl-3'-nitro-1-nitrosoguanidine (MNNG) . Compound 23N inhibited the mutagenicity of BaP and MNNG . The antimutagenic activity of 2A was limited to MNNG . Mutat Res, 1998 Sep 11, 417(2-3), 95 - 100 Genotoxicity of Farbasol and its component: 4-ethyltoluene; Janik-Spiechowicz E et al.; A combination of assays for gene mutations in Salmonella typhimurium TA97a, TA98, TA100 and TA102 strains with and without rat liver activation, and for micronucleus and sister chromatid exchange (SCE) in bone marrow cells of Imp:Balb/c mice was used to provide data on the mutagenic and genotoxic properties of the mixture of aromatic solvents, known under the trade name of Farbasol . In addition, 4-ethyltoluene (the main ethylmethylbenzenic component of Farbasol) was also tested for muta- and genotoxicity . The results revealed that neither Farbasol nor 4-ethyltoluene induced an increased reverse mutation in bacterial cells or the formation of micronucleated polychromatic erythrocytes in bone marrow . However, those compounds were found to be active as sister chromatid exchange (SCE) agents . Mutat Res, 1998 Sep 11, 417(2-3), 75 - 84 Modulatory effects of melatonin on genotoxic response of reference mutagens in the Ames test and the comet assay; Musatov SA et al.; The effect of a potent endogenous antioxidant, the pineal gland indole melatonin (MLT) on the mutagenicity of twelve well-known mutagens and carcinogens has been investigated using two in vitro tests the Ames test and the single cell gel electrophoresis assay (SCGE assay or COMET assay) . The 12 mutagens used were 7, 12-dimethylbenz(a)anthracene (DMBA), benzo(a)pyrene (BP), 2-aminofluorene (AF), 1,2-dimethylhydrazine (DMH), bleomycin, cyclophosphamide (CP), 4-nitroquinoline-N-oxide (NQO), 2,4, 7-trinitro-9-fluorenone (TNF), 9-aminoacridine (AA), N-nitrosomethylurea (NMU), mitomycin C and sodium azide tested in the absence or in the presence of S9 mix . MLT alone turned out neither toxic nor mutagenic in the Ames test and revealed clastogenic activity at the highest concentration tested (100 microM) in the SCGE assay . In four Salmonella typhimurium tester strains TA 97, TA 98, TA 100 and TA 102 MLT significantly reduced the mutagenicity of chemicals which require S9 activation . In the SCGE assay performed on CHO cells, preincubation with MLT led to a strong inhibition of clastogenic activities of DMBA and CP, and in a lesser extent with BP and NMU . With mitomycin C, MLT exacerbated responses in both tests . The possible mechanisms of MLT's inhibitory action are discussed . J Biol Chem, 1998 Sep 18, 273(38), 24575 - 82 Identification and characterization of a sialidase released by the salivary gland of the hematophagous insect Triatoma infestans; Amino R et al.; Sialidases (EC 3.2.1.18) are commonly found in viruses, bacteria, fungi, protozoa, and vertebrates, but not in invertebrates . We have previously reported the presence of a new sialidase activity in the gut of exclusively hematophagous insects of the Triatoma genus, which transmit Chagas' disease (Amino, R., Acosta, A., Morita, O . M., Chioccola, V . L . P., and Schenkman, S . (1995) Glycobiology 5, 625-631) . Here we show that this sialidase is present in the salivary gland of Triatoma infestans, and it is released with the saliva during the insect bite . The sialidase was purified to homogeneity (>5000 times) to a specific activity of more than 20 units/mg . It elutes from a gel filtration column with a volume corresponding to the size of 33 kDa, and it migrates as a single 26-kDa band in SDS-polyacrylamide gel electrophoresis, which is unusually smaller when compared with other known sialidases . T . infestans sialidase hydrolyzes preferentially alpha2-->3-linked sialic acids at pH 4-8, with maximal activity between pH 5.5 and 6.5, which is compatible with the optimal pH of secreted sialidases . The sialidase is competitively inhibited by 2-deoxy-2, 3-dehydro-N-acetyl-neuraminic acid (Ki = 0.075 mM) and differently from many sialidases, with exception of Salmonella typhimurium sialidase, it is inhibited competitively by HEPES (Ki = 15 mM) . The fact that T . infestans sialidase is released with the saliva and can hydrolyze sialyl-LewisX blood groups, which are the ligands for selectins, suggests that it might have a role in the blood feeding. J Bacteriol, 1998 Sep, 180(18), 4775 - 80 Mutations in Salmonella pathogenicity island 2 (SPI2) genes affecting transcription of SPI1 genes and resistance to antimicrobial agents; Deiwick J et al.; The Salmonella typhimurium genome contains two pathogenicity islands (SPI) with genes encoding type III secretion systems for virulence proteins . SPI1 is required for the penetration of the epithelial layer of the intestine . SPI2 is important for the subsequent proliferation of bacteria in the spleens of infected hosts . Although most mutations in SPI2 lead to a strong reduction of virulence, they have different effects in vitro, with some mutants having significantly increased sensitivity to gentamicin and the antibacterial peptide polymyxin B . Previously we showed that certain mutations in SPI2 affect the ability of S . typhimurium to secrete SPI1 effector proteins and to invade cultured eukaryotic cells . In this study, we show that these SPI2 mutations affect the expression of the SPI1 invasion genes . Analysis of reporter fusions to various SPI1 genes reveals highly reduced expression of sipC, prgK, and hilA, the transcriptional activator of SPI1 genes . These observations indicate that the expression of one type III secretion system can be influenced dramatically by mutations in genes encoding a second type III secretion system in the same cell. J Med Chem, 1998 Sep 10, 41(19), 3748 - 52 Anthracene-9,10-diones as potential anticancer agents: bacterial mutation studies of amido-substituted derivatives reveal an unexpected lack of mutagenicity; Venitt S et al.; Fifteen anthracene-9,10-dione ("anthraquinone") derivatives with (omega-aminoalkyl)carboxamido substituents at the 1-, 2-, 1,4-, or 2, 6-ring positions were tested for bacterial mutagenicity in reverse-mutation assays using Salmonella typhimurium frameshift strains TA1538, TA98, and TA97a, in the presence and absence of a metabolic activation system prepared from the livers of rats treated with Aroclor 1254 . Six of the compounds were also tested in S . typhimurium TA100 and Escherichia coli WP2uvrApKM101 strains, which carry mutations particularly sensitive to reversion by DNA base-pair substitution . Two structurally related compounds, mitoxantrone and bisantrene, were tested in parallel as positive controls . Mitoxantrone was mutagenic to S . typhimurium TA1538 and TA98, whereas bisantrene was weakly mutagenic to both these strains but strongly mutagenic toward the TA97a variant . By contrast, although they are also DNA-binding intercalators, none of the amide-functionalized anthracene-9,10-diones of the present study showed significant mutagenic activity in any of the bacterial strains examined . Further, neither substituent position nor systematic alterations in the nature of attached side chains appeared to induce mutagenicity with these agents, although other studies have shown that such structural factors markedly influence their cytotoxic potencies toward mammalian cells in vitro. J Rheumatol, 1998 Sep, 25(9), 1765 - 71 HLA-B27 does not affect invasion of arthritogenic bacteria into human cells; Ortiz-Alvarez O et al.; OBJECTIVE: To investigate the effect of HLA-B27 expression on entry of Salmonella typhimurium and Yersinia enterocolitica into human cells . METHODS: We performed standard bacterial invasion assays with S . typhimurium and Y enterocolitica to analyze isogenic pairs of HeLa (epithelial), U937 (promonocyte), C1R (B lymphocyte), and Jurkat (T lymphocyte) human cell lines and their respective HLA-B27 transfectants . Invasion of peripheral blood derived T lymphocytes, monocytes, and B lymphocytes/dendritic cell fraction (corresponding to peripheral blood cells depleted of monocytes and T lymphocytes) from patients with ankylosing spondylitis and healthy donors was also analyzed . The percentage of internalized bacteria was quantified, and the differences between HLA-B27 positive and negative samples were compared . RESULTS: The percentages of intracellular S . typhimurium and Y enterocolitica in HeLa, U937, and C1R with or without B27 were not statistically different (independent t test) . We also found that the percentage of internalized bacteria did not differ significantly between HLA-B27 positive and negative samples in the different populations of peripheral blood derived cells . CONCLUSION: The presence of HLA-B27 on the surface of human cells does not alter the degree of bacterial invasion into either cultured human cell lines or peripheral blood derived human cells, and the influence of HLA-B27 expression on bacterial invasion should not be implicated in the pathogenesis of reactive arthritis related to Salmonella and Yersinia. Indian J Exp Biol, 1998 Jun, 36(6), 588 - 92 Effect of gamma irradiation on chemical and biological properties of lipopolysaccharide from Salmonella typhimurium; Naidu MD et al.; Lipopolysaccharide (LPS) from S . typhimurium on exposure to gamma-radiation resulted in decrease in toxicity and was less mitogenic, Silver stained profiles of irradiated LPS on polyacrylamide gels revealed complete loss of its heteropolysaccharides which was confirmed further by analysing lipid A and LPS from Salmonella minnesota Re mutants on SDS-PAGE . Glucosamine and 2-keto 3-deoxy-octonate(Kdo) contents were significantly decreased on treatment . Lipid A obtained by removal of heteropolysaccharides from LPS was less toxic on exposure to gamma radiations. Mutat Res, 1998 Aug 14, 416(3), 169 - 81 Comparisons of chemically-induced mutation among four bacterial strains, Salmonella typhimurium TA102 and TA2638, and Escherichia coli WP2/pKM101 and WP2 uvrA/pKM101: collaborative study III and evaluation of the usefulness of these strains; Watanabe K et al.; Over the past 5 years, a large collaborative study of chemically-induced mutation has been performed using the four bacterial strains Salmonella typhimurium TA102 and TA2638 and Escherichia coli WP2/pKM101 and WP2 uvrA/pKM101 in order to compare the specific spectrum of response to chemicals and to evaluate the usefulness (sensitivity) of each strain . Following the two collaborative studies to test the chemicals in category 1, chemicals previously judged as positive only in E . coli WP2 strains and derivatives of these chemicals, and category 2, oxidative agents or crosslinking agents, 22 compounds of category 3 consisting of 10 nonmutagenic carcinogens and another 12 chemicals were selected in this study . Twenty participating laboratories tested each compound in the same method as previous reports . In the group of nonmutagenic carcinogens, no chemical induced revertant colonies of any strain tested . In the group of other chemicals, response to the chemicals was similar in TA102 and WP2 uvrA/pKM101 . Overall, in the three collaborative studies, a total of 79 compounds were tested . No difference in qualitative response to the four strains was observed for 71% (56/79) of the test chemicals . The combination of strains providing the greatest number of positive responses was WP2 uvrA/pKM101 with TA102; 84% (66/79) of the test chemicals elicited the same qualitative response in these two strains . Therefore, it is suggested that WP2 uvrA/pKM101 and TA102 can be included as a part of the standard tester strains for detection of mutagenic activity of chemicals . Mutat Res, 1998 Aug 14, 416(3), 149 - 57 Inhibitory effect of threo-9,10-dichlorostearic acid on the mutagenic activity of MeIQx, 2-AF and B{a}P in the Ames/Salmonella test; Vereskuns G et al.; The mutagenic activity of threo-9,10-dichlorostearic acid, one of the chlorinated fatty acids identified in fish lipids, was examined in the Ames/Salmonella test . No mutagenic activity was found on any of the Salmonella typhimurium strains TA 98, TA 100 and TA 102, either with or without S9 activation . On the other hand, dichlorostearic acid showed an inhibitory effect on the mutagenic activity of the indirectly-acting mutagens 2-amino-3, 8-dimethylimidazo{4,5-f}quinoxaline (MeIQx), 2-aminofluorene (2-AF) and benzo{a}pyrene (B{a}P) using strain TA 98 in the presence of S9 . However, no inhibition was observed when mixing MeIQx and S9 before the addition of dichlorostearic acid . Furthermore, dichlorostearic acid did not show any inhibitory effect on the mutagenic activity of the directly-acting mutagen 4-nitroquinoline-N-oxide (4NQO) using the tester strains TA 98 and TA 100 . We, therefore, suggest that dichlorostearic acid interacts with the enzymes of the S9 mix, thereby dose-dependently inhibiting the transformation of MeIQx, 2-AF and B{a}P into their active forms . Mutat Res, 1998 Sep 1, 417(1), 31 - 7 Genotoxic activity of chlorinated butenoic acids in Salmonella typhimurium strains TA98, TA100 and TA104; Franzen R et al.; The mutagenic activities of several chlorinated butenoic acids, recently identified in chlorinated drinking waters, were determined by the Salmonella microsome assay . The Salmonella typhimurium tester strains TA98, TA100, and TA104 were used without S9 mix . The results from the investigation showed that (Z)-2-chloro-3-(dichloromethyl)-4-oxobutenoic acid (MX, in the open form) was the most potent mutagen of the compounds tested . However, a significant number of mutations was also induced by compounds with structural similarities to MX . In general, all the compounds, except the butenedioic acids, were mutagenic in the assays for both base-pair substitution strains (TA100, TA104) and for the frameshift strain TA98, with the highest mutagenic response observed in strain TA100 . When the aldehyde group of MX and of 2-chloro-3-(chloromethyl)-4-oxobutenoic acid (CMCF, in the open form) was replaced by a dichloromethyl group, the mutagenic response in strains TA98 and TA104 changed . We concluded that a frame-shift mutation occurred because of the replacement . The increase of the TA104 mutagenicity suggested that adenosine could be the target for these types of compounds . Further evidence for such possibility were the modified adenosine adducts we could identify for some chlorinated butenoic acids . Appl Environ Microbiol, 1998 Sep, 64(9), 3458 - 63 Induction of acid resistance of Salmonella typhimurium by exposure to short-chain fatty acids; Kwon YM et al.; Exposure to short-chain fatty acids (SCFA) is one of the stress conditions Salmonella typhimurium encounters during its life cycle, because SCFA have been widely used as food preservatives and SCFA are also present at high concentrations in the gastrointestinal tracts of host animals . The effects of SCFA on the acid resistance of the organism were examined in an attempt to understand the potential role of SCFA in the pathogenesis of S . typhimurium . The percent survival of S . typhimurium at pH 3.0 was determined after exposure to SCFA for 1 h at pH 7.0 . The percent acid survival, which varied depending on the SCFA species and the concentration used, was 42 after exposure to 100 mM propionate at pH 7.0 under aerobic incubation conditions, while less than 1% could survive without exposure . The SCFA-induced acid resistance was markedly enhanced by anaerobiosis (64%), lowering pH conditions (138% at pH 5.0), or increasing incubation time (165% with 4 h) during exposure to propionic acid . When protein synthesis during exposure to propionate was blocked by chloramphenicol, the percent acid survival was less than 1, indicating that the protein synthesis induced by exposure to propionate is required for the induction of the acid resistance . The percent acid survival determined with the isogenic mutant strains defective in acid tolerance response revealed that AtrB protein is necessary for the full induction of acid resistance by exposure to propionate, while unexpectedly, inactivation of PhoP significantly increased acid resistance over that of the wild type (P < 0.05) . The results suggest that the virulence of S . typhimurium may be enhanced by increasing acid resistance upon exposure to SCFA during its life cycle and further enhanced by anaerobiosis, low pH, and prolonged exposure time. Indian J Pathol Microbiol, 1995 Oct, 38(4), 365 - 8 In vitro susceptibility of multiple drug resistant Salmonella typhimurium to newer fluroquinolone derivatives; Shetty M et al.; A total of 105 strains of Salmonella typhimurium resistant to Ampicillin, Co-trimoxazole and Nalidixic acid were included in the present study . Among the new line of Fluroquinolones resistance to Ciprofloxacin (3.8%), Norflox (16.19%) and Ofloxacin (24.76%) was very low as compared to older antibiotics . All the 3 fluoroquinolones had MIC values less than 1 mcg/ml. Mutat Res, 1998 Jul 17, 403(1-2), 223 - 7 Genotoxicity of ribo- and deoxyribonucleosides of 8-hydroxyguanine, 5-hydroxycytosine, and 2-hydroxyadenine: induction of SCE in human lymphocytes and mutagenicity in Salmonella typhimurium TA 100; Arashidani K et al.; The induction of SCE by ribo- and deoxyribonucleosides of 8-hydroxyguanine, 5-hydroxycytosine, and 2-hydroxyadenine was tested using human peripheral blood lymphocytes . All of these compounds caused an increase in SCE frequency . The potency of SCE induction was as follows: 5-OH-C, 5-OH-dC > 8.OH-G > 8-OH-dG > 2-OH-A, 2-OH-dA . These results suggest that the oxidized nucleosides are incorporated into DNA with different efficiencies (or are repaired with different efficiencies) and exhibit genotoxicity in human blood cells . Ribo- and deoxyribo-derivatives of 5-OH-Cyt and 2-OH-Ade also showed mutagenic activity in Salmonella typhimurium TA 100. Mutat Res, 1998 Aug 7, 416(1-2), 125 - 8 Inhibition of PhIP mutagenicity by caffeine, lycopene, daidzein, and genistein; Weisburger JH et al.; The heterocyclic amine 2-amino-1-methyl-6-phenylimidazo{4,5-beta}pyridine NPhIP) is a major dietary component in individuals eating cooked meats or fish . This heterocyclic amine requires biochemical activation, mainly through cytochrome P4501A2, and can be detoxified chiefly by 4'hydroxylation through other cytochromes, and be in turn converted through phase 2 enzymes to readily excreted conjugates . The active form of PhIP is mutagenic in Salmonella typhimurium TA98 and is a useful substrate to study the possible chemoprotective action of phytochemicals . We found that black and green tea depressed the mutagenicity of PhIP in dose-related fashion, and decaffeinated tea was less powerful an inhibitor . This led to the study of caffeine, that displayed effective dose-related inhibition of the mutagenicity of PhIP . Other antioxidants such as lycopene, the active antioxidant from tomatoes, and daidzein and genistein from soy products, also had a dose-related inhibition of the mutagenicity of PhIP . We conclude that PhIP is a good substrate found in several human foods to determine the protective effect of phytochemicals from vegetables, and beverages. Mutat Res, 1998 Aug 7, 416(1-2), 11 - 9 Antimutagenic activity of carotenoids in green peppers against some nitroarenes; Gonzaez de Mejia E et al.; In Mexico, as well as in Central and South American countries, the consumption of peppers (Capsicum annuum) has been tradition for thousands of years; the per capita dietary intake of peppers is about 40 g/day . Peppers are an important source of beta-carotene and vitamin A, which have antimutagenic and/or anticarcinogenic properties . In the present study, Salmonella typhimurium tester strain YG1024 in the plate-incorporation test was used to examine the antimutagenicity of carotenois extracted from five different types of Capsicum spp . ('Chilaca', 'Poblano', 'Serrano', 'Jalapeno' and 'Pimiento') which were chosen, based on their consumption and availability on the local market . Extracts from these peppers were tested against 1-6-dinitropyrene (1,6-DNP) and 1,8-dinitropyrene (1,8-DNP) mutagenicity . Dose-response mutagenicity curves of 1-NP; 1,6-DNP and 1,8-DNP were obtained . For the antimutagenicity studies, doses of 0.05 microgram/plate, 0.20 ng/plate and 0.06 ng/plate for 1-NP, 1,6-DPN and 1,8-DNP respectively were chosen, and the number of net revertants/plate were 1008 for 1-NP, 512 for 1,6-DNP, and 712 for 1,8-DPN . Trans-beta-carotene and the extracts were not toxic to the bacteria at the concentrations tested . The extracts obtained from the peppers showed more inhibition than pure trans-beta-carotene on 1-NP; 1,6-DNP and 1,8-DNP mutagenicity . Chilaca pepper extract required 0.36 g (34 nmol expressed as trans-beta-carotene equivalents) of fresh pepper to inhibit 94% on 1-NP mutagenicity, 78% on 1,6-DNP mutagenicity and 84% on 1,8-DNP mutagenicity . Bell pepper ('Pimiento') extract required 1.53 g (50 nmol expressed as trans-beta-carotene) to obtain 87%, 79% and 73% inhibition on 1-NP; 1,6-DNP and 1,8-DNP mutagenicity respectively . Since pure beta-carotene inhibited only approximately 50% the mutagenicity of nitroarenes, these results suggest that each one of the pepper extracts have more than one antimutagenic compound (e.g., beta-carotene and xanthophylls) and those functional nutrients apparently have a synergistic effect. Int J Parasitol, 1998 Jul, 28(7), 1121 - 30 Progress in recombinant vaccine development against coccidiosis . A review and prospects into the next millennium; Vermeulen AN; The increasing problems encountered by the poultry industry, despite the extensive use of drugs, have emphasised the need for an immunological solution for the economic damage caused by the Eimeria parasite . Although immunity develops relatively fast following a natural infection, to induce protection by using parasite extracts or single antigens appears more difficult . Nevertheless, the development of a vaccine based on defined antigens seems the best solution in the long run . At the VIth International Coccidiosis Conference in 1993 the first promising results were reported from small-scale experiments using recombinant antigens . This review summarises the advances in this field of research from 1993 onwards . Although since then not many reports have been published about the effects of using recombinant . antigens as a vaccine against coccidiosis, a number of interesting new proteins which could be considered good targets for such a vaccine have been described and are referred to herein . Proteins involved in the process of invasion of the host cell by the extracellular parasite are regarded as key components in the developmental cycle of the parasite . These components possibly bind to receptors on the host cell . Interference with this process could be a target of the protective immune response . Progress has also been made in characterising the immune mechanisms activated by infection with the parasite . From experimental mouse models and from studies in chickens, a better insight has been obtained towards the involvement of CD4- and CD8-type T cells in, respectively, the inductor and the effector branch of the immune response, although not all questions have been answered . Several antigens have been selected using T-cell stimulation and cytokine assays and these are reviewed . In a third section, mostly unpublished results of our own experiments dealing with the use of live vectors to present defined antigens such as Ea1A and EaSC2, a parasite refractile body transhydrogenase and a lactate dehydrogenase, respectively, are summarised . Partial protection could be induced using Salmonella typhimurium as a carrier for these antigens, in that the oocyst output was reduced by up to 50% after challenge and weight gain could be improved by 5-10% over non-vaccinated challenged chickens, when tested in a floor-pen trial . Similar results were obtained when these antigens were presented by viral vectors such as Fowlpox virus or Herpes virus of turkey . These data seem to offer good prospects for the accomplishment of a safe and efficaceous vaccine based on recombinant DNA technology . These expectations are corroborated by recent breakthrough in transfection of related parasites such as Plasmodium and Toxoplasma gondii, and by the increasing amount of genomic information becoming available every day, the impact of which cannot even be estimated yet . These new technologies will allow us to solve the complex problems that we once created ourselves. J Bacteriol, 1998 Sep, 180(17), 4757 - 9 The panE gene, encoding ketopantoate reductase, maps at 10 minutes and is allelic to apbA in Salmonella typhimurium; Frodyma ME et al.; In Salmonella typhimurium, precursors to the pyrimidine moiety of thiamine are synthesized de novo by the purine biosynthetic pathway or the alternative pyrimidine biosynthetic (APB) pathway . The apbA gene was the first locus defined as required for function of the APB pathway (D . M . Downs and L . Petersen, J . Bacteriol . 176:4858-4864, 1994) . Recent work showed the ApbA protein catalyzes the NADPH-specific reduction of ketopantoic acid to pantoic acid . This activity had previously been associated with the pantothenate biosynthetic gene panE . Although previous reports placed panE at 87 min on the Escherichia coli chromosome, we show herein that apbA and panE are allelic and map to 10 min on both the S . typhimurium and E . coli chromosomes . Results presented here suggest that the role of ApbA in thiamine synthesis is indirect since in vivo labeling studies showed that pantoic acid, the product of the ApbA-catalyzed reaction, is not a direct precursor to thiamine via the APB pathway. J Bacteriol, 1998 Sep, 180(17), 4750 - 2 Gene transfer between related bacteria by electrotransformation: mapping Salmonella typhi genes in Salmonella typhimurium; Toro CS et al.; Transfer of newly isolated mutations into a fresh background is an essential step of genetic analysis and strain construction . Gene transfer is hampered in Salmonella typhi and in other pathogenic bacteria by the lack of a generalized transduction system . We show here that this problem can be partially circumvented by using electrotransformation as a means for delivering S . typhi DNA into suitable S . typhi or Salmonella typhimurium recipients . Transferred DNA can recombine with the homologous region in the host chromosome . In one application of the method, mutations isolated in S . typhi were genetically mapped in S . typhimurium. J Bacteriol, 1998 Sep, 180(17), 4686 - 92 Multidrug efflux pump AcrAB of Salmonella typhimurium excretes only those beta-lactam antibiotics containing lipophilic side chains; Nikaido H et al.; We found that the previously reported SS-B drug-supersusceptible mutant of Salmonella typhimurium (S . Sukupolvi, M . Vaara, I . M . Helander, P . Viljanen, and P . H . Makela, J . Bacteriol . 159:704-712, 1984) had a mutation in the acrAB operon . Comparison of this mutant with its parent strain and with an AcrAB-overproducing strain showed that the activity of the AcrAB efflux pump often produced significant resistance to beta-lactam antibiotics in the complete absence of beta-lactamase . The effect of AcrAB activity on resistance was more pronounced with agents containing more lipophilic side chains, suggesting that such compounds were better substrates for this pump . This correlation is consistent with the hypothesis that only those molecules that become at least partially partitioned into the lipid bilayer of the cytoplasmic membrane are captured by the AcrAB pump . According to this mechanism, the pump successfully excretes even those beta-lactams that fail to traverse the cytoplasmic membrane, because these compounds are likely to become partitioned into the outer leaflet of the bilayer . Even the compounds with lipophilic side chains were shown to penetrate across the outer membrane relatively rapidly, if the pump was inactivated genetically or physiologically . The exclusion of such compounds, exemplified by nafcillin, from cells of the wild-type S . typhimurium was previously interpreted as the result of poor diffusion across the outer membrane (H . Nikaido, Biochim . Biophys . Acta 433:118-132, 1976), but it is now recognized as the consequence of efficient pumping out of entering antibiotics by the active efflux process. J Bacteriol, 1998 Sep, 180(17), 4564 - 70 Promoter substitution and deletion analysis of upstream region required for rpoS translational regulation; Cunning C et al.; The RpoS sigma factor of enteric bacteria is required for the increased expression of a number of genes that are induced during nutrient limitation and growth into stationary phase and in response to high osmolarity . RpoS is also a virulence factor for several pathogenic species, including Salmonella typhimurium . The activity of RpoS is regulated at both the level of synthesis and protein turnover . Here we investigate the posttranscriptional control of RpoS synthesis by using rpoS-lac protein and operon fusions . Substitution of the native rpoS promoters with the tac or lac UV5 promoters allowed essentially normal regulation after growth into stationary phase in rich medium or after osmotic challenge . Regulation of these fusions required the function of hfq, encoding the RNA-binding protein host factor I (HF-I) . Short deletions from the 5' end of the rpoS transcript did not affect regulation very much; however, a larger deletion mutation that still retains 220 bp upstream of the rpoS ATG codon, including a proposed antisense element inhibitory for rpoS translation, was no longer regulated by HF-I . Several models for regulation of rpoS expression by HF-I are discussed. FEBS Lett, 1998 Aug 7, 432(3), 228 - 30 Unfolding of bacteriophage P22 tailspike protein: enhanced thermal stability of an N-terminal fusion mutant; Carbonell X et al.; The tailspike protein (TSP) of bacteriophage P22 is a homotrimeric multifunctional protein responsible for cell attachment and hydrolysis of the Salmonella typhimurium host cell receptor . Despite the folding of TSP involves the formation of thermolabile intermediates, the mature protein is extremely resistant to heat and detergent denaturation . We have analyzed the thermal resistance and unfolding pathway of two mutant, functional TSPs carrying end-terminal peptide fusions . Whereas the C-terminal fusion has minor effects on the TSP stability, the presence of a 23-mer foreign peptide at the N terminus (protein ATSP) results in a significant enhancement of the thermal resistance by retarding the first transition step of the unfolding process . At 65 degrees C and in 2% SDS, the unfolding rate constant for the transition from the native to the unfolding intermediate is 9.3 x 10(-4) s(-1) for ATSP versus 1.7 x 10(-3) s(-1) for wild-type TSP . On the other hand, the electrophoretic mobility of ATSP intermediates is greatly affected, proving structural modifications induced by the fused peptide . These results suggest a critical participation of the N-terminal domain in the unfolding kinetic barriers generated during the TSP denaturation pathway. Mol Microbiol, 1998 Jul, 29(2), 641 - 52 Limits to inducer exclusion: inhibition of the bacterial phosphotransferase system by glycerol kinase; Rohwer JM et al.; The uptake of methyl alpha-D-glucopyranoside by the phosphoenolpyruvate-dependent phosphotransferase system of Salmonella typhimurium could be inhibited by prior incubation of the cells with glycerol . Inhibition was only observed for glycerol preincubation times longer than 45 s and required the preinduction of both the glucose and the glycerol-catabolizing systems . Larger extents of inhibition by glycerol correlated with higher intracellular levels of glycerol kinase when the glp regulon had been induced to different extents . Preincubation with lactate did not inhibit methyl alpha-D-glucopyranoside uptake significantly, although both lactate and glycerol were oxidized by the cells . The cellular free-energy state of the cells (intracellular {ATP}/{ADP} ratio) was virtually identical for lactate and glycerol preincubation, suggesting that the inhibition of phosphotransferase-mediated uptake was not a metabolic effect . In vitro, phosphotransferase activity was inhibited to a maximal extent of 32% upon titrating cell-free extracts with high concentrations of commercial glycerol kinase . The results show that uptake systems that have hitherto been regarded merely as targets of the phosphotransferase system component IIA(Glc) also have the capacity themselves to retroinhibit the phosphotransferase system flux, presumably by sequestration of the available IIA(Glc), provided that these systems are induced to appropriate levels. J Chemother, 1998 Aug, 10(4), 313 - 9 Successful treatment of murine listeriosis and salmonellosis with levofloxacin; Nichterlein T et al.; Levofloxacin (L-ofloxacin) is a fluoroquinolone derivative . It is the active substance contained in ofloxacin with a broad spectrum of antibacterial activity against both Gram-negative and Gram-positive bacteria . In this work we examined the activity of levofloxacin against the facultative intracellular bacteria Listeria monocytogenes and Salmonella typhimurium in vitro, in tissue culture and in animal models of infection . The minimum inhibitory concentrations (MICs) MIC90 for Salmonella enterica and L . monocytogenes were 0.078 mg/l and 4 mg/l, respectively . Levofloxacin was bactericidal against L . monocytogenes and S . typhimurium because 8 x MIC killed 90% of the initial inoculum of L . monocytogenes EGD and S . typhimurium LT2 within 4 hours and 3 hours, respectively . Levofloxacin was more effective than ampicillin against L . monocytogenes EGD infecting tissue culture cells . Also in tissue culture cells infected with S . typhimurium LT2, levofloxacin was slightly more effective than ciprofloxacin . In animal models of infection, levofloxacin was as potent as the reference substances . In conclusion, levofloxacin is a candidate for the treatment of infections caused by facultative intracellular Gram-positive and Gram-negative bacteria. Biosci Biotechnol Biochem, 1998 Jul, 62(7), 1425 - 7 Suppression of the SOS-inducing activity of Trp-P-1 and aflatoxin B1 by meso-dihydroguaiaretic acid from Machilus thunbergii in the Salmonella typhimurium TA1535/pSK1002 umu test; Miyazawa M et al.; The methanol extract from Machilus thunbergii showed a suppressive effect on umu gene expression of the SOS response in Salmonella typhimurium TA1535/pSK1002 against the mutagen, 3-amino-1,4-dimethyl-5H-pyrido{4,3-b}indole (Trp-P-1), which requires liver metabolizing enzymes . The methanol extract from M . thunbergii was successively re-extracted with chloroform, butanol and water . A suppressive compound in the chloroform extract fraction was isolated by SiO2 column chromatography and identified as meso-dihydroguaiaretic acid by GC-MS, and 1H- and 13C-NMR spectroscopy . Meso-dihydroguaiaretic acid inhibited of the SOS-inducing activity of Trp-P-1 in the umu test . Gene expression was suppressed by 62% at less than 0.18 mumol/ml, the ID50 value being 0.08 mumol/ml . Compound 1 was also assayed with aflatoxin B1 (AfB1) and showed a suppressive effect. Commun Dis Public Health, 1998 Mar, 1(1), 28 - 30 Protracted outbreak of Salmonella typhimurium definitive phage type 170 food poisoning related to tripe, 'pig bag', and chitterlings; Cornell J et al.; An outbreak of food poisoning around South Yorkshire due to Salmonella typhimurium definitive phage type 170 related to eating tripe, 'pig bag', and chitterlings was associated with a common supplier . Possible links with other suppliers were considered . Twenty-two cases occurred between 11 April 1995 and 7 May 1995 . The situation was complicated by the complex distribution network of suppliers and by possible cross contamination in the retail outlets . This complexity created difficulties in the collection, recording and subsequent analysis of the data . The investigation of the outbreak and the subsequent control measures are discussed . Some of the difficulties of monitoring foodborne intestinal disease are highlighted. J Appl Microbiol, 1998 Jun, 84(6), 988 - 98 Assessment of bacterial viability status by flow cytometry and single cell sorting; Caron GN et al.; Rapid bacterial detection and viability measurements have been greatly enhanced by recent advances in the use of fluorescent stains in cytometry . It has previously been shown that four physiological states can be distinguished: reproductively viable, metabolically active, intact and permeabilized . Previous sorting experiments have shown that not all intact cells readily grow, but some intact cells can grow even when they fail to show metabolic activity, as determined by esterase turnover . To circumvent the limitations imposed by active dye extrusion or cell dormancy on viability measurements used to date (e.g., enzyme activity or cell polarization), a fast triple fluorochrome staining procedure has been developed that takes account of these problems . This allows further cellular characterization of intact cells by: active exclusion of ethidium bromide (EB) (metabolically active cells), uptake of EB but exclusion of bis-oxonol (BOX) (de-energized but with a polarized cell membrane) and uptake of both dyes (depolarized) . Permeabilized cells were identified by propidium iodide (PI) uptake . The method was validated using an electronically programmable single cell sorter (EPICS Elite) and aged Salmonella typhimurium cells . Reproductive viability was determined by sorting single cells to their staining pattern directly onto agar plates . Most polarized cells could be recovered as well as a significant fraction of the depolarized cells, demonstrating that depolarization is a sensitive measure of cell damage but a poor indicator of cell death. Mutagenesis, 1998 Jul, 13(4), 385 - 9 Inhibition of metabolic activation of the promutagens, benzo{a}pyrene, 2-aminofluorene and 2-aminoanthracene by furanochromones in Salmonella typhimurium; Schimmer O et al.; Khellin, a naturally occurring furanochromone (Ammi visnaga fruits), inhibited the mutagenicity of the promutagens benzo{a}pyrene, 2-aminofluorene and 2-aminoanthracene in Salmonella typhimurium TA98 . The effect varied greatly and depended on the S9 fraction used . Cytosolic activation of 2-aminoanthracene was also inhibited . Khellin produced no effect or only weak activity against the direct acting mutagens 2-nitrofluorene, 4-nitro-o-phenylenediamine, 1-nitropyrene and ethylmethane sulfonate (in TA100) . Daunomycin mutagenicity was inhibited to a greater extent . Visnagin was more toxic, but showed similar effects . Khellol and its glucoside were inactive against all the mutagens tested . We conclude that khellin acts as an inhibitor or the microsomal cytochrome P450 sub-enzymes analogous to the related furanocoumarins and is also capable of inhibiting cytosolic enzymes . The extract from Ammi visnaga fruits showed a higher inhibition potency than khellin alone against 2-aminoanthracene, 1-nitropyrene and daunomycin . This might be due to additional inhibitors, e.g . coumarins, or to the synergistic effects of accompanying compounds. Scand J Immunol, 1998 Aug, 48(2), 136 - 43 Priming of T-cell responses in mice by porins of Salmonella typhimurium; Gupta S; An imbalance in signals delivered to T cells via T-cell receptor and accessory molecules can lead to anergy, apoptosis, or both . In the present study we have demonstrated that Salmonella typhimurium infection in mice leads to a progressive loss of CD4+ T helper (Th) cell population, abnormal T-cell death by apoptosis and loss of accessory molecules (B7 and intracellular adhesion molecule-1) on macrophages . Quantification of interleukin-2 (IL-2), interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) secretion revealed a Th2-type of response in lymphocytes isolated from spleen . However, preimmunization of mice with porins resulted in an increased CD4+ Th cell population and accessory molecules on the surface of macrophages . Quantification of cytokines revealed a Th1-type of response . We conclude that preimmunization of mice with porins provides a microenvironment in which a well-balanced accessory molecule and cytokine network is established, which results in the prevention of cell death by apoptosis. Mutat Res, 1998 Jul 31, 415(3), 201 - 11 Lack of mammalian mutagenicity of the potent bacterial mutagen tris(2,3-dibromopropyl) phosphate and its metabolite 2-bromoacrolein; van Beerendonk GJ et al.; The flame retardant tris(2,3-dibromopropyl)phosphate (Tris-BP) and its metabolite 2-bromoacrolein (2BA) are very potent bacterial mutagens in Salmonella typhimurium (S . typhimurium) TA 100 . In this study, we showed that 2BA and Tris-BP are also mutagenic in S . typhimurium TA 104, which detects mutations at AT base pairs, while TA 100 detects mutations at CG basepairs . We also studied the mutagenicity of 2BA in mammalian cells in vitro and in the rat in vivo . Firstly, 2BA was tested in the human lymphoblastoid cell line TK6 . The results showed that there was no increase in mutation frequency at the hprt locus, whereas there was a large decrease in cell survival . Secondly, a shuttle vector system was used to study the induction of mutations by 2BA:DNA adducts . The vector was modified by insertion of a single-stranded oligonucleotide containing on average one 2BA:DNA adduct . No increase in mutation frequency above background was detected after replication of this vector in SV40 transformed normal human fibroblasts . Because the liver is a major site for bioactivation of Tris-BP to 2BA in vivo, we tested the initiating capacity of Tris-BP in the rat liver in a modified Solt & Farber initiation and promotion system . Administration of Tris-BP resulted in a small increase in the number of preneoplastic gamma-glutamyl-transpeptidase positive (GGT+) foci in the liver compared to control animals (only significant in the lowest size class) . Modification of the experimental protocol by performing partial hepatectomy 24 h after the administration of Tris-BP, did not increase the number of GGT+ or glutathione S-transferase-P (GST-P+) positive foci above the control level . Taken together, these results indicate that, in spite of a high mutagenicity in S . typhimurium, 2BA and Tris-BP have low or negligible mutagenic effects in mammalian systems . The lack of mutagenic activity may explain why Tris-BP is not a carcinogen in the rat liver. Ann Occup Hyg, 1998 May, 42(4), 259 - 66 Chemical degradation of wastes of antineoplastic agents amsacrine, azathioprine, asparaginase and thiotepa; Barek J et al.; As a part of a program devoted to the destruction of antineoplastic agents, three chemical methods readily available in the hospital environment, viz . oxidation with sodium hypochlorite (NaClO, 5%), hydrogen peroxide (H2O2, 30%), and Fenton reagent (FeCl2.2H2O; 0.3 g in 10 ml H2O2, 30%), were tested for the degradation of four anticancer drugs: Amsacrine, Azathioprine, Asparaginase and Thiotepa . The efficiency of the degradation was monitored by high-performance liquid chromatography . The mutagenicity of the degradation residues were tested by Ames test using tester strains Salmonella typhimurium TA 97a, TA 98, TA 100 and TA 102 with and without an exogenous metabolic activation system . Using sodium hypochlorite, 98.5% of Amsacrine, 99.0% of Azathioprine, 99.5% of Asparaginase and 98.7% of Thiotepa were destroyed after 1 hr . The hydrogen peroxide treatment destroyed 99% of Asparaginase and 98.7% of Thiotepa in 1 hr . However, this procedure was not efficient for the treatment of Amsacrine (28% after 16 hr) and of Azathioprine (53% degradation in 4 hr) . The action of Fenton reagent resulted in the destruction of 98% of Amsacrine, and 99.5% of Azathioprine, 98.5% of Asparaginase and 98.7% of Thiotepa in 1 hr . In all cases where a high degree of degradation was achieved, the residues obtained weee non mutagenic. Mutat Res, 1998 Jul 8, 415(1-2), 119 - 30 The mutagenic activity of unpolymerized resin monomers in Salmonella typhimurium and V79 cells; Schweikl H et al.; Dimethacrylate derivatives are used as monomers to polymerize dental composite materials and for a great variety of other industrial resins . Occupational exposure is likely in various ways because of the many areas of methacrylate application . Here, the mutagenicity of the monomers, bisphenol A-diglycidyl dimethacrylate (Bis-GMA), urethane dimethacrylate (UDMA), triethylene glycol dimethacrylate (TEGDMA), Bisphenol A (BPA), glycidyl methacrylate (GMA), methyl methacrylate (MMA), and 2-hydroxyethyl methacrylate (HEMA) was studied in a bacterial (Ames test) and a mammalian gene mutation assay (V79/HPRT assay) . Mutagenicity was determined in different Salmonella typhimurium strains (TA97a, TA98, TA100, TA102) and in V79 cells in the presence and in the absence of a metabolically active microsomal fraction from rat liver (S9) . No mutagenic effects were observed with Bis-GMA and UDMA, methyl methacrylate, 2-hydroxyethyl methacrylate and bisphenol A . Glycidyl methacrylate (GMA) was mutagenic in a dose-dependent manner in three Salmonella tester strains . The number of mutants was increased by a factor of 2 to 3 with strains TA97a and TA102 in the absence of S9 . Moreover, the numbers of mutants induced in S . typhimurium TA100 were about 8-fold higher than in solvent controls . GMA also induced an increase of mutants in V79 cells in the absence of S9 . However, GMA was inactivated by microsomal enzymes . Triethylenglycol dimethacrylate (TEGDMA) was not mutagenic in any S . typhimurium . In contrast, the compound induced a dose-dependent rise in mutant frequencies in V79 cell cultures . It is concluded that TEGDMA acted through a clastogenic mechanism which is not detected by Ames tester strains. Mutat Res, 1998 Jul 8, 415(1-2), 13 - 23 Mutagenic and cytotoxic effects of exhaust particulate matter of biodiesel compared to fossil diesel fuel; Bunger J et al.; The mutagenic and cytotoxic effects of diesel engine exhaust (DEE) from a modern passenger car using rapeseed oil methyl esters (RME, biodiesel) as fuel were directly compared to DEE of diesel fuel (DF) derived from petroleum . Combustion particulate matter was collected on glass fiber filters coate