Differential gene expression in culturable and non-culturable Salmonella typhimurium

Differential gene expression in culturable and non-culturable forms of Salmonella typhimurium was studied by the molecular display method. Six fragments of differentially expressed gene cDNA, depending on culturable or non-culturable state of the cultures, were isolated, cloned, and sequenced. Identification of corresponding S. typhimurium differentially expressed genes was carried out by comparing the sequences of cDNA fragments with the bacterial genome data base.     

Induction of umu gene expression in Salmonella typhimurium TA1535/pSK1002 by dimethyl sulfoxide (DMSO)

The genotoxicity of dimethyl sulfoxide (DMSO) was demonstrated by the umu test using Salmonella typhimurium TA1535/pSK1002 carrying the umuC-lacZ fusion gene. The level of beta-galactosidase activity which shows umu gene expression in the test system was dependent on the concentration of DMSO in the culture medium. The maximum beta-galactosidase activity was approximately 3.5 times as high as the background level with 10% of DMSO in the culture medium. The lowest concentration of DMSO required for a response of over twice the background level was approximately 5%. Four structurally related chemicals (acetone, di-n-butylsulfoxide, dimethylsulfide, methylphenylsulfoxide) did not show umu gene expression at their non-toxic doses.     

Induction of P22 Prophage in Salmonella typhimurium by Hycanthone

Hycanthone was found to be an inducer of P22 prophage in Salmonella typhimurium LT-2(P22).     

Mutagenesis by neocarzinostatin in Escherichia coli and Salmonella typhimurium: requirement for umuC+ or plasmid pKM101.

Neocarzinostatin, a protein with antibiotic activity, is a bacterial mutagen. We have investigated the mutagenicity of neocarzinostatin towards Salmonella typhimurium and discovered that, unlike the situation in Escherichia coli, neocarzinostatin will revert base pair substitution mutations (missense or nonsense). However, when the R46 factor derivative, plasmid pKM101, was introduced, the mutagenicity of neocarzinostatin towards base pair substitution-carrying mutants of S. typhimurium was readily detected. Neocarzinostatin had only modest activity in reverting a frameshift mutation in S. typhimurium, but that activity, too, required the presence of pKM101. Mutant pKM101 plasmids which no longer enhanced mutagenesis also lost their ability to promote neocarzinostatin-induced mutations. Finally, the umuC36 mutation, which renders E. coli nonmutable by ultraviolet light, also rendered the bacteria nonmutable by neocarzinostatin. The effect of the umuC36 mutation was suppressed by plasmid pKM101.     

Location of a mutator gene in Salmonella typhimurium by cotransduction

Kirchner, Carl E. J. (Suffolk County Community College, Selden, N.Y.), and Matthew J. Rudden. Location of a mutator gene in Salmonella typhimurium by cotransduction. J. Bacteriol. 92:1453-1456. 1966.-The LT7 strain of Salmonella typhimurium has been shown to possess a mutator gene which is responsible for an increase in mutation frequency for most loci tested. Preliminary results suggested the gene might be responsible for the production of an abnormal purine or pyrimidine base. Phage prepared on the mutator strain were used to transduce selected purine and pyrimidine LT2 mutants that do not possess this gene. A high frequency (60%) of cotransduction was observed with mutants from only one locus, purA. Transduction of additional mutants from this region gave similar results, except for one mutant (purA1) which showed no transduction of the mutator gene or the purA1 region. The results show that the mutator gene is very closely linked to the purA locus and suggest that it might be part of it.     

Role of hypoxanthine and guanine in regulation of Salmonella typhimurium pur gene expression.

Crystal violet (hexamethyl-para-rosaniline chloride) interacts with aqueous KI-I2 during the Gram stain via a simple metathetical anion exchange to produce a chemical precipitate. There is an apparent 1:1 stoichiometry between anion (I-) and cation (hexamethyl-para-rosaniline+) during the reaction and, since the small chloride anion is replaced by the bulkier iodide, the complex formed becomes insoluble in water. It is this same precipitate which forms in the cellular substance of bacteria (both gram-positive and gram-negative types) and which initiates the Gram reaction. Potassium trichloro(eta 2-ethylene)-platinum(II), as an electronopaque marker for electron microscopy, was chemically synthesized, and it produced an anion in aqueous solution which was compatible with crystal violet for the Gram stain. It interacted with crystal violet in a similar manner as iodide to produce an insoluble complex which was chemically and physically analogous to the dye-iodide precipitate. This platinum anion therefore allows the Gram staining mechanism to be followed by electron microscopy.     

Control of arg gene expression in Salmonella typhimurium by the arginine repressor from Escherichia coli K-12

Summary The regulation of synthesis of arg enzymes in Salmonella typhimurium by the arginine repressor of Escherichia coli K-12 has been reevaluated using a strain of S. typhimurium in which the argR gene was rendered nonfunctional by inserting the translocatable tetracyclineresistance element Tn10 into the argR gene. In contrast to previous studies, the introduction of the argR ⁺ allelle of E. coli on an F-prime factor to the argR::Tn10 S. typhimurium strain reduced the synthesis of arg enzymes to essentially wild-type levels. The elevated levels of arg enzymes observed in other hybrid merodiploids may have been the consequence of the formation of hybrid repressor molecules. The readily scoreable phenotype of tetracycline resistance facilitated establishing linkage of cod and argR (0.6% cotransduction) by P22 phage-mediated transduction.     

Comparison of Cytokine Induction by Lipopolysaccharide of Bacteroides fragilis with Salmonella typhimurium in Mice

Comparison of cytokine stimulation by lipopolysaccharide (LPS) of Bacteroides fragilis and Salmonella typhimurium was done to study the early events occurring in vivo. Mice injected intraperitoneally with either LPS demonstrated endogenous production of all the cytokines studied (tumor necrosis factor-alpha, interferon-gamma and interleukin-6) within 6 hr in the bloodstream. However induction of all the cytokines by B. fragilis LPS (50 μg/mouse) was much weaker compared with S. typhimurium LPS (50 μg/mouse). Even a dose of S. typhimurium LPS 40 times smaller (1.2 μg/mouse) induced cytokines more strongly compared with B. fragilis LPS. Thus, a weak biological response to B. fragilis LPS as evidenced by chick embryo lethality, limulus lysate gelation, LD₅₀ for mice and rabbit pyrogenicity could be due to weak induction of bioactive mediators by LPS.