O-antigen chain-length distribution in Salmonella enterica serovar Enteritidis is regulated by oxygen availability.

Abstract Lipopolysaccharide (LPS) consists of three covalently linked domains: the lipid A, the core region and the O antigen (OAg), consisting of repeats of an oligosaccharide. Salmonella enterica serovar Enteritidis ( S . Enteritidis) produces a LPS with two OAg preferred chain lengths: a long (L)-OAg controlled by Wzz SE and a very long (VL)-OAg controlled by Wzz fepE . In this work, we show that OAg produced by S . Enteritidis grown in E minimal medium also presented two preferred chain-lengths. However, a simultaneous and opposing change in the production of L-OAg and VL-OAg was observed in response to oxygen availability. Biochemical and genetics analyses indicate that this process is regulated by transcriptional factors Fnr and ArcA by means of controlling the transcription of genes encoding Wzz SE and Wzz fepE in response to oxygen availability. Thus, our results revealed a sophisticated regulatory mechanism involved in the adaptation of S . Enteritidis to one of the main environmental cues faced by this pathogen during infection.