Proc. Natl Acad. Sci. USA (2014)

For bacteria, maintaining the structural integrity of the cell wall is essential for survival. Human cells have membranes instead of walls, so disrupting cell-wall synthesis is a neat way of targeting bacterial infection. Now, Ariel Amir and co-workers have found that cell-wall growth influences how bacterial cells deform in response to external stress.

Amir et al. grew Escherichia coli and Bacillus subtilis cells in microchannels and suppressed their division so that they continued to elongate. The team then subjected them to hydrodynamic forces and showed that the cells behaved like elastic rods under transient (pulse-like) forces, but deformed plastically when subjected to longer lasting forces. In both cases, the cells recovered their native shape, although the plastically deformed cells only did so following substantial cell-wall synthesis.

Based on their keen observation that previously reported plastic deformations involved constraining cells for longer than their mass-doubling time, the authors hypothesized that deformations were plastic only when the wall had adequate time to grow under force. Their theoretical framework confirmed what their experiments demonstrated: when force was applied for long enough, coupling between mechanical stress and wall synthesis caused the differential growth that resulted in plastic deformation.