Investigating Bacterial Deformation Upon Surface Attachment Using Finite Element Modeling

Bacteria adhere to different surfaces and, upon sensing the surface, transition to a biofilm state. Studies have shown that bacteria sense a mechanical cue upon surface adhesion, resulting in deformation of the cell envelope that can be transduced by mechanosensitive proteins. Direct experimental measurement of nanoscopic deformation in micron-scale bacteria is difficult. Hence, we develop finite element modeling to estimate the bacterial deformations due to adhesion. We model bacteria as thin-walled pressure vessels, using physical properties reported in the literature, that adhere to substrates via a van der Waals force. By varying shape, physical properties, and envelope thickness, we can model attachment mechanics of different bacterial strains. Particularly we explore P. aeruginosa (rod-shaped; Gram-negative), B. subtilis (rod-shaped; Gram-positive), and S. aureus (spherical; Gram-positive). We expect this modeling to shed light on mechanisms of and potential for surface sensing. For example, we find that attachment to a rigid surface can increase normal stress on the P. aeruginosa cell envelope by one order of magnitude. This, and the corresponding thinning of the envelope, likely give rise to surface sensing.