Salmonella serovar Typhimurium causes acute cecal inflammation and takes advantage of host immune responses to establish infection. In PLoS Pathogens, Bäumler and colleagues find that host inflammation confers enhanced competitive fitness to bacteria that express Tsr and Aer, two methyl-accepting chemotaxis proteins. The generation of reactive oxygen species by neutrophils leads to the production of tetrathionate, a sulfur compound that Salmonella can use as an electron acceptor during anaerobic respiration. Nitric oxide is also produced during inflammation and reacts with reactive oxygen species to generate nitrates. Aer and Tsr are able to sense higher concentrations of tetrathionate and nitrate, respectively, and direct chemotaxis toward their source at the mucosal epithelium. Because of their ability to use such molecules as electron acceptors in respiration, Salmonella have a growth advantage over resident bacteria, conferred by Aer and Tsr. Thus, unwittingly, host inflammatory responses aid infecting Salmonella by creating unique niches that the bacteria exploit.

PLoS Pathog. 9. e1003267 (18 April 2013)