Bacterial Virulence

ReseaRch highlights

Nature Reviews Microbiology | AoP, published online 12 october 2010; doi:10.1038/nrmicro2464

Bacterial virulence Gaining an edge in the gut Two articles, published in Nature and to tetrathionate by a strong oxidiz- metabolize ethanolamine in the Environmental Microbiology, highlight ing agent. As neutrophils produce intestines of cows to gain a growth the use of specific compounds in the oxidizing agents in the form of advantage. Ethanolamine is an intestine by two different pathogens nitric oxide radicals and reac- abundant nutrient derived from the to outcompete the native flora. tive oxygen species, the authors phosphatidylethanolamine in the Salmonella enterica subsp. enterica speculated that tetrathionate might membranes of intestinal cells that serovar Typhimurium causes inflam- be produced during inflammation. are sloughed off the intestinal wall. mation in the intestine, and Winter Indeed, when mice were infected EHEC can use this ethanolamine and colleagues now show that the with an S. Typhimurium mutant that as a nitrogen source. However, the bacterium utilizes the tetrathionate cannot use tetrathionate, the authors native bacterial population of the cow that is produced as a result of this detected tetrathionate in the gut; gastrointestinal tract, which includes host response. Tetrathionate has been no tetrathionate was detected after other strains of E. coli, does not used for nearly 90 years to enrich infection with wild-type bacteria, seem to use ethanolamine efficiently. Salmonella spp. in cultures, as this presumably because it was depleted Competition experiments using bacterium, unlike many others, can by the bacteria. Inflammation and the wild-type EHEC and mutant EHEC use this compound as a terminal production of reactive oxygen species that are unable to use ethanolamine electron acceptor. Normally no were required for tetrathionate pro- show that ethanolamine utilization tetrathionate is present in the gut. duction, as mutant bacteria unable provides a distinct growth advantage. However, thiosulphate, which is to induce inflammation did not Thus, pathogens can benefit from produced in the intestines from the induce tetrathionate production, and the exploitation of a nutritional niche hydrogen sulphide secreted by no tetrathionate was produced in mice in the gastrointestinal tract. This is the gut microbiota, can be converted deficient in gp91phox (also known likely to be a common mechanism as CYBB), an important component by which pathogens gain an edge in in the formation of reactive oxygen colonization of the host. species. Competition assays revealed Christiaan van Ooij that, in the presence of tetrathionate, wild-type bacteria have a distinct OriGinal reSearcH PaPerS Winter, S. E. et al. Gut inflammation provides a respiratory growth advantage over bacteria that electron acceptor for Salmonella. Nature 467, cannot use tetrathionate, both in vitro 426–429 (2010) | Bertin, Y. et al. Enterohaemorrhagic and in an in vivo mouse model. Thus, Escherichia coli gains a competitive advantage by using ethanolamine as a nitrogen source in the induction of inflammation by the bovine intestinal tract. Environ. Microbiol. S. Typhimurium results in the pro- 16 Sep 2010 (doi: 10.1111/j.1462‑2920.2010.02334.x) FurtHer readinG Garsin, D. A. Ethanolamine duction of a compound that gives the utilization in bacterial pathogens: roles and bacterium a selective advantage. regulation.. Nature Rev. Microbiol. 8, 290–295 Similarly, Bertin and colleagues (2010) | Croxen, M. A. & Finlay, B. B. Molecular mechanisms of Escherichia coli pathogenicity. show that enterohaemorrhagic Nature Rev. Microbiol. 8, 26–38 (2010) Escherichia coli (EHEC) can