Is there a Role for Mechanosensitive Channels in Formation and Maintenance of Bacterial Biofilms?

Abstract

Bacteria are among the most successful organisms to inhabit Earth. Their world is filled with mechanical cues probably the most ancient of which are osmotic forces. To cope with osmotic forces bacteria have developed mechanosensitive (MS) channels, which play essential role in osmoregulation and provide one of the simplest paradigms for the study of mechanosensory transduction. In my talk, I will discuss the structure and function of bacterial MS channels including the alternative mechano-sensory responses that they may mediate in complex microbial communities, such as bacterial biofilms. Mechanical forces modulate the formation of biofilms and the shear stresses applied from fluid flow regulate these communities. Although a recent transcriptomic analysis of E. coli suggests that many genes are differentially modulated by shear flow, the levels of MS channel genes seemed not to be affected. Nevertheless, given that the bacteria in the biofilm emit an electrical signal (i.e. the release of K+) and there are five MscS-like homologues in E. coli of unknown physiological function these MS channels may play an important role in the biofilms. In fact, the MscS-like MscK channel is regulated by external ionic environment, requiring high concentrations of external K+, Rb+, Cs+ or NH4+ for its activation by membrane tension, which suggests its more specialized physiological role compared to MscS or MscL channels, whose physiological role in bacterial osmoregulation has been firmly established. Furthermore, results linking bacterial MS channels to biofilm formation have been reported showing that ablation of the quorum sensing system in Pseudomonas aeruginosa, affects biofilm formation and downregulates MscK expression. These findings apparently link the MscK expression and function to adhesive forces and metabolic cues within a biofilm and may also explain how mechanical forces determine biofilm development and maintenance.