Mechanical stress compromises multicomponent efflux complexes in bacteria.

Area of Science:

• Microbiology
• Biophysics
• Cell Biology

Background:

• Mechanical forces influence eukaryotic cell physiology, but their role in prokaryotes remains largely unknown.
• Physical forces affect bacterial shape, division, motility, virulence, and biofilm formation, yet molecular mechanisms are unclear.
• Gram-negative bacteria possess multicomponent protein complexes spanning the cell envelope, making them susceptible to mechanical stress.

Purpose of the Study:

• To investigate how mechanical forces applied to the bacterial cell envelope are translated at the molecular level.
• To determine the effect of mechanical stress on the function of transenvelope protein complexes in bacteria.
• To elucidate the impact of mechanical forces on bacterial susceptibility to metal toxicity.

Main Methods:

• Manipulation of tensile and shear mechanical stress in the bacterial cell envelope of *Escherichia coli*.
• Single-molecule tracking to observe protein complex dynamics under stress.
• Assessment of bacterial susceptibility to copper and silver toxicity.

Main Results:

• Octahedral shear stress, but not hydrostatic stress, within the cell envelope promotes the disassembly of the tripartite efflux complex CusCBA.
• Disassembly of CusCBA by mechanical forces increases bacterial susceptibility to copper and silver toxicity.
• Mechanical forces can inhibit the function of cell envelope protein assemblies in bacteria.

Conclusions:

• Mechanical forces directly regulate the function of bacterial cell envelope protein complexes, such as the CusCBA efflux system.
• Mechanical stress has the potential to modulate bacterial survival and growth by affecting protein assembly function.
• Transenvelope efflux complexes involved in antibiotic resistance and other vital processes may also be mechanosensitive.