Taneja Swadhin, Levitan Benjamin A, Rutenberg Andrew D
Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4R2.
Phys Rev E Stat Nonlin Soft Matter Phys. 2014 Jan;89(1):012704. doi: 10.1103/PhysRevE.89.012704. Epub 2014 Jan 7.
We have modeled stress concentration around small gaps in anisotropic elastic sheets, corresponding to the peptidoglycan sacculus of bacterial cells, under loading corresponding to the effects of turgor pressure in rod-shaped bacteria. We find that under normal conditions the stress concentration is insufficient to mechanically rupture bacteria, even for gaps up to a micron in length. We then explored the effects of stress-dependent smart autolysins, as hypothesized by A. L. Koch [ Adv. Microb. Physiol. 24 301 (1983); Res. Microbiol. 141 529 (1990)]. We show that the measured anisotropic elasticity of the peptidoglycan (PG) sacculus can lead to stable circumferential propagation of small gaps in the sacculus. This is consistent with the recent observation of circumferential propagation of PG-associated MreB patches in rod-shaped bacteria. We also find a bistable regime of both circumferential and axial gap propagation, which agrees with behavior reported in cytoskeletal mutants of B. subtilis. We conclude that the elastic anisotropies of a bacterial sacculus, as characterized experimentally, may be relevant for maintaining rod-shaped bacterial growth.
我们对各向异性弹性薄片中小间隙周围的应力集中进行了建模，这些间隙对应于细菌细胞的肽聚糖囊泡，加载情况对应于杆状细菌中膨压的影响。我们发现，在正常条件下，即使对于长达一微米的间隙，应力集中也不足以使细菌机械破裂。然后，我们探讨了如A. L. Koch所假设的应力依赖性智能自溶素的作用[《微生物生理学进展》24 301（1983年）；《微生物学研究》141 529（1990年）]。我们表明，所测得的肽聚糖（PG）囊泡的各向异性弹性可导致囊泡中小间隙的稳定周向扩展。这与最近在杆状细菌中观察到的与PG相关的MreB斑块的周向扩展一致。我们还发现了周向和轴向间隙扩展的双稳态机制，这与枯草芽孢杆菌细胞骨架突变体中报道的行为相符。我们得出结论，实验表征的细菌囊泡的弹性各向异性可能与维持杆状细菌生长有关。
