Utilization of D-xylose by wild-type strains of Salmonella typhimurium

Comparison of Phenotype Nutritional Profiles and Phosphate Metabolism Genes in Four Serovars of Salmonella enterica from Water Sources

The surveillance of foods for Salmonella is hindered by bias in common enrichment media where serovars implicated in human illness are outgrown by less virulent serovars. We examined four Salmonella serovars, two common in human illness (Enteritidis and Typhimurium) and two that often dominate enrichments (Give and Kentucky), for factors that might influence culture bias. The four serovars had similar growth kinetics in Tryptic Soy Broth and Buffered Peptone Water. Phenotype microarray analysis with 950 chemical substrates to assess nutrient utilization and stress resistance revealed phenotype differences between serovars. Strains of S. Enteritidis had better utilization of plant-derived sugars such as xylose, mannitol, rhamnose, and fructose, while S. Typhimurium strains were able to metabolize tagatose. Strains of S. Kentucky used more compounds as phosphorus sources and grew better with inorganic phosphate as the sole phosphorus source. The sequences of nine genes involved in phosphate metabolism were compared, and there were differences between serovars in the catalytic ATP-binding domain of the histidine kinase phoR. Analysis of the predicted PhoR amino acid sequences from additional Salmonella genomes indicated a conservation of sequences each within the Typhimurium, Give, and Enteritidis serovars. However, three different PhoR versions were observed in S. Kentucky.

Meso-tartrate resistance and phylogenetic relationships of biotypes of Salmonella typhimurium

Meso-tartrate utilizing and resistant (mT+) recombinants were produced readily in transductions from an mT+donor strain to 42 naturally occurringmeso-tartrate non-utilizing and sensitive (mT−) recipient strains ofSalmonella typhimurium, and were produced, sometimes as frequently, in interbiotype crosses between different pairs of strains from the mT−biotypes 2, 18, 26 and of the FIRN group (biotypes 30 and 32). These findings suggested that the sites of themtamutations were independent in strains from the different mT−biotypes and were in agreement with their probable different lines of descent. Intrabiotype crosses indicated genetic homogeneity among strains of biotype 26 and among strains of biotype 30; on the other hand, they suggested that in each of the biotypes 2, 18 and 32, a minority of strains hadmtamutations present at different intragenic sites from those of the majority of strains. The derivations of the strains of the minority types are discussed.

Transduction of inositol-fermenting ability demonstrating phylogenetic relationships among strains of Salmonella typhimurium

The production of Inl+recombinants was readily demonstrated in transductional crosses from Inl+donor strains to Inl−recipient strains from different biotypes and biogroups. None of numerous crosses between different pairs of strains from biotypes 25 and 26 and the biogroup FIRN (biotypes 29, 30, 31 and 32) gave Inl+recombinants suggesting that theinlmutation was present at the same intragenic site in all of these strains. Strains of the FIRN biogroup (Fim−Inl−Rha−Bxyl−) are thought to have descended by successiverhaandfimmutations from an ancestral bacterium of biotype 25 (Fim+Inl−Rha+Bxyl−). The sites of theinlmutations in other Inl−biotypes (9, 10, 27 and 25hi) were independent and each was different from that in strains from biotypes 25, 26 and FIRN.