Inefficient Secretion of Anti-Sigma Factor FlgM Inhibits Bacterial Motility at High Temperature

Abstract

Temperature is one of the key cues that enable microorganisms to adjust their physiology in response to environmental changes. Here we show that motility is the major cellular function of Escherichia coli that is differentially regulated between growth at normal host temperature of 37°C and the febrile temperature of 42°C. We demonstrate that this downregulation primarily occurs due to the malfunction of secretion apparatus, apparently related to the disassembly of the flagellar basal body. This prevented secretion of the anti-sigma factor FlgM and resulted in FlgM-dependent repression of class III motility genes at 42°C, while enabling prompt reactivation of motility upon decrease of temperature. We hypothesize that E. coli perceives high temperature as a sign of inflammation, downregulating flagella to escape detection by immune system of the host. Secretion-dependent coupling of gene expression to the environmental temperature represents a novel mode of stress response, which is likely to be common among many bacterial species.