Mechanically-driven phase separation in a growing bacterial colony
Mechanically-driven phase separation in a growing bacterial colony
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DOI：
10.1073/pnas.1504948112
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发表时间：
2015-04-28
影响因子：
11.1
通讯作者：
Levine, Herbert
中科院分区：
文献类型：
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作者：
Ghosh, Pushpita;Mondal, Jagannath;Levine, Herbert
生长细菌分泌的胞外聚合物(EPSS)是形成生物膜样结构的重要组成部分。在这种稠密的系统中，结构组件之间的机械相互作用可以显著地影响形态特性。在这里，我们使用基于粒子的建模方法来研究在固体底物上生长的不活动的杆状细菌细胞在自身产生的EPSS存在下的自组织。在我们的模拟中，所有组件都通过排斥力进行机械相互作用，发生在细菌细胞生长和分裂(通过消耗扩散的营养物质)并产生EPSS时。基于我们的模拟，我们证明了机械相互作用控制着系统的集体行为。特别是，我们发现非吸附EPSS的存在可以通过耗竭吸引导致细菌细胞的自发聚集，从而在非平衡生长的菌落中产生相分离模式。细胞和EPSS之间的排斥作用和EPSS的总浓度都是非平衡生长群体中自组织的重要因素。此外，我们研究了机械与细菌细胞的营养扩散和消耗的相互作用，并观察到与不产生EPS的情况相比，EPSS抑制了分支的形成。
Secretion of extracellular polymeric substances (EPSs) by growing bacteria is an integral part of forming biofilm-like structures. In such dense systems, mechanical interactions among the structural components can be expected to significantly contribute to morphological properties. Here, we use a particle-based modeling approach to study the self-organization of nonmotile rod-shaped bacterial cells growing on a solid substrate in the presence of self-produced EPSs. In our simulation, all of the components interact mechanically via repulsive forces, occurring as the bacterial cells grow and divide (via consuming diffusing nutrient) and produce EPSs. Based on our simulation, we show that mechanical interactions control the collective behavior of the system. In particular, we find that the presence of nonadsorbing EPSs can lead to spontaneous aggregation of bacterial cells by a depletion attraction and thereby generates phase separated patterns in the nonequilibrium growing colony. Both repulsive interactions between cell and EPSs and the overall concentration of EPSs are important factors in the self-organization in a nonequilibrium growing colony. Furthermore, we investigate the interplay of mechanics with the nutrient diffusion and consumption by bacterial cells and observe that suppression of branch formation occurs due to EPSs compared with the case where no EPS is produced.