Siderophore production by environmental strains of Salmonella species

Iron uptake mechanisms were investigated in different species of Salmonella isolated from environmental waters. All strains examined were able to grow in the presence of high concentrations (10 mM) of the iron chelator EDDA. All strains excreted phenolate and hydroxamate siderophores, as assessed by bioassays and chemical tests. Bioassays with different indicator strains showed that all Salmonella strains can cross-feed other Enterobacteria, as well as mutants of Salmonella typhimurium deficient in the Enterobactin system, suggesting that this siderophore may be produced by the environmental Salmonella strains. The siderophore aerobactin may also be produced by one of the strains, according to the bioassays results. The same pattern of outer membrane proteins are synthesized under iron-limiting conditions in all species tested, which suggests a similarity of iron uptake systems in many species of Salmonella. This system could be also of great importance in the survival of these bacteria in natural waters, as well as in possible pathogenic mechanisms.