Bacteria usually grow in populations to survive in various environments. A yet unsolved issue is how mechanical forces at the cellular level regulate the morphogenesis of bacterial population. In this paper, we combine experiments and theoretical analysis to investigate the growth of bacterial chains constituted by rod-shaped Bacillus subtilis. Our experiments show that due to cellular proliferation-induced compressive forces, one-dimensional bacterial chains can buckle into a morphology similar to toppling dominoes. A rod–spring model which considers both cell–cell connection and cell–substrate interaction is established to study the buckling behaviors of bacterial chains. The critical features at the growth-induced instability of bacterial chains are determined by the energetic competition associated with elastic strain energy and cell–substrate bonding energy. An active rod method is further presented to simulate the bacterial growth dynamics from a single bacterium to a chain structure and, subsequently, to a two-dimensional biofilm, where Johnson–Kendall–Roberts theory is adopted to account for intercellular contact forces. This work suggests a novel mechanism of instability in the self-organization and expansion of bacterial biofilms.

细菌通常在人群中生长以在各种环境中生存。一个尚未解决的问题是细胞水平的机械力如何调节细菌种群的形态发生。在本文中，我们结合实验和理论分析来研究杆状枯草芽孢杆菌构成的细菌链的生长。我们的实验表明，由于细胞增殖引起的压缩力，一维细菌链可以弯曲成类似于倒塌多米诺的形态。建立了同时考虑细胞-细胞连接和细胞-底物相互作用的杆-弹簧模型来研究细菌链的屈曲行为。生长诱导的细菌链不稳定的关键特征取决于与弹性应变能和细胞-基质键合能相关的高能竞争。进一步提出了一种主动杆法来模拟细菌从单个细菌到链结构，然后到二维生物膜的生长动力学，其中采用Johnson-Kendall-Roberts理论来解释细胞间的接触力。