Active interface bulging in Bacillus subtilis swarms promotes self-assembly and biofilm formation

• 成果类型: Article
• 署名作者: Liu, Siyu; Li, Ye; Xu, Haoran; Kearns, Daniel B.; Wu, Yilin
• 署名单位: Chinese University of Hong Kong; Chinese Academy of Sciences; Shenzhen Institute of Advanced Technology, CAS; Indiana University System; Indiana University Bloomington
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-10901
• DOI: 10.1073/pnas.2322025121
• 发表日期: 2024-07-30
• 关键词: cell-fate; surface; GROWTH; colonization; fluctuations; microscopy; bacteria; waves

摘要

Microbial communities such as biofilms are commonly found at interfaces. However, it is unclear how the physical environment of interfaces may contribute to the development and behavior of surface-associated microbial communities. Combining multimode imaging, single-cell tracking, and numerical simulations, here, we found that activity-induced interface bulging promotes colony biofilm formation in Bacillus subtilis swarms presumably via segregation and enrichment of sessile cells in the bulging area. Specifically, the diffusivity of passive particles is similar to 50% lower inside the bulging area than elsewhere, which enables a diffusion-trapping mechanism for self-assembly and may account for the enrichment of sessile cells. We also uncovered a quasilinear relation between cell speed and surface-packing density that underlies the process of active interface bulging. Guided by the speed-density relation, we demonstrated reversible formation of liquid bulges by manipulating the speed and local density of cells with light. Over the course of development, the active bulges turned into striped biofilm structures, which eventually give rise to a large-scale ridge pattern. Our findings reveal a unique physical mechanism of biofilm formation at air-solid interface, which is pertinent to engineering living materials and directed self-assembly in active fluids.