Mechanical stress compromises multicomponent efflux complexes in bacteria

Abstract

Physical forces have a profound effect on growth, morphology, locomotion, and survival of organisms. At the level of individual cells, the role of mechanical forces is well recognized in eukaryotic physiology, but much less is known about prokaryotic organisms. Recent findings suggest an effect of physical forces on bacterial shape, cell division, motility, virulence, and biofilm initiation, but it remains unclear how mechanical forces applied to a bacterium are translated at the molecular level. In Gram-negative bacteria, multicomponent protein complexes can form rigid links across the cell envelope and are therefore subject to physical forces experienced by the cell. Here we manipulate tensile and shear mechanical stress in the bacterial cell envelope and use single-molecule tracking to show that octahedral shear (but not hydrostatic) stress within the cell envelope promotes disassembly of the tripartite efflux complex CusCBA, a system used byEscherichia colito resist copper and silver toxicity. By promoting disassembly of this protein complex, mechanical forces within the cell envelope make the bacteria more susceptible to metal toxicity. These findings demonstrate that mechanical forces can inhibit the function of cell envelope protein assemblies in bacteria and suggest the possibility that other multicomponent, transenvelope efflux complexes may be sensitive to mechanical forces including complexes involved in antibiotic resistance, cell division, and translocation of outer membrane components. By modulating the function of proteins within the cell envelope, mechanical stress has the potential to regulate multiple processes required for bacterial survival and growth.

Effects of Nanopillar Size and Spacing on Mechanical Perturbation and Bactericidal Killing Efficiency

“…Moreover, there is evidence to suggest that different types of mechanical stress will stimulate different mechanosensitive mechanisms in bacteria. For instance, by applying selective loading modes, Genova, et al [18] demonstrated that octahedral shear stress, in particular, promotes the disassembly of efflux pumps and can render bacteria more susceptible to antimicrobials. Finite element modelling, to resolve the complex stress state of the envelope, could be paired with proteomic analyses, such as those in Genova, et al [18] and Jenkins, et al [13], to better understand the role of mechanical stress in bacteria-nanopattern inactivation.…”

“…Accordingly, it is understood that nanopatterned surfaces kill bacteria by inducing-through contact-mechanical stress and strain in the envelope which exceeds a survivable limit [12,17]. Whether death is the result of only rupture, or also other mechanosensitive physiological effects remains a topic of ongoing study [13,18].…”

Mechanical Stabilization of a Bacterial Adhesion Complex

“…Gram-positive pathogenic bacteria produce cell wall-anchored (CWA) surface proteins that are important for the bacteria to colonize the host and promote infections. , The most prevalent CWA proteins are the microbial surface components recognizing adhesive matrix molecules (MSCRAMMs), which are critical in bacterial “adhesion, invasion, and immune evasion.” During colonization and infection, these MSCRAMM-mediated adhesions are subjected to mechanical forces associated with flow stress induced by the dynamic oscillated blood pressure, airflow, and other hydrostatic pressures. − The tensile forces applied to a single adhered bacterial cell span over a wide range of magnitude, from the nanonewton (nN) range in the urinary tract needed to withstand the high speed of urinary flow down to piconewton (pN) in capillaries according to the reported shear stress. , …”

Engineered Living Hydrogels

“…[ 116 ] Compared to cells in soft hydrogels, the cell growth rate decreases in stiff hydrogels with a high Young's modulus. [ 43,116,117 ] The elongation of rod‐shaped microbial cells is inhibited by the hydrogel matrix, although the cells can remain metabolically active ( Figure a, left). [ 116 ] At a higher cell density, the repulsive forces between microbial cells and EPS‐based biopolymers lead to spontaneous cell aggregation in the hydrogels owing to the effect of macromolecular crowding.…”