The Rcs-regulated colanic acid capsule maintains membrane potential in Salmonella enterica serovar Typhimurium
Pando, Jasmine M.
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The Rcs phosphorelay and Psp (phage shock protein) systems are envelope stress responses that are highly conserved in γ-proteobacteria. The Rcs regulon was found to be strongly induced during metal deprivation of Salmonella enterica serovar Typhimurium lacking the Psp response. Nineteen genes activated by the RcsA-RcsB response regulator comprise an operon responsible for production of colanic acid capsular polysaccharide, which promotes biofilm development. Despite more than half a century of research, the physiological function of colanic acid has remained elusive. In this study we provide evidence that Rcs-dependent colanic acid production maintains the transmembrane electrical potential (Δψ) and proton motive force (PMF) in cooperation with the Psp response. Production of negatively-charged exopolysaccharide covalently bound to the outer membrane may enhance the surface potential by increasing the local proton concentration. This provides a unifying mechanism to account for diverse Rcs/colanic acid-related phenotypes, including susceptibility to membrane-damaging agents and biofilm formation. This work provides a new and fundamental insight into bacterial physiology.
- Microbiology