A significant role for Sigma B in the detergent stress response of Listeria monocytogenes

Aims: To investigate the contribution of the alternative sigma factor Sigma B to detergent stress in Listeria monocytogenes upon exposure to the surface-active agents, benzalkoniumchloride (BC), cetylpyridinium chloride (CPC) and sodium docecyl sulfate (SDS). Methods and Results: Surfactant/detergent stress in L. monocytogenes 10403S and a ΔsigB mutant of 10403S was investigated by lethality, impact on growth and by transcriptional analysis. We observed a significant 1-2 log decrease in the viability of the ΔsigB mutant in response to lethal levels of surfactants. Transcriptional (reverse transcriptase-PCR) analysis revealed the induction of sigmaB by sublethal levels of surface-active agents. However, Sigma B does not play a significant role in the growth of L. monocytogenes upon exposure to sublethal levels as investigated by growth analysis. Conclusions: Sigma B is essential for the resistance of L. monocytogenes at lethal levels of BC, CPC and SDS. Significance and Impact of the Study: We demonstrate that Sigma B is essential for the resistance of the pathogen to surfactant stress. The findings raise the possibility that induction of Sigma B by sublethal levels of industrial cleaning agents may promote enhanced resistance of further food-processing associated stresses or conditions encountered during infection. Sigma B-regulated mechanisms of detergent resistance may provide targets for the future design of novel cleaning agents.