In nature, bacteria form biofilms-differentiated multicellular communities attached to surfaces. Within these generally sessile biofilms, a subset of cells continues to express motility genes. We found that this subpopulation enabled Bacillus subtilis biofilms to expand on high-friction surfaces. The extracellular matrix (ECM) protein TasA was required for the expression of flagellar genes. In addition to its structural role as an adhesive fiber for cell attachment, TasA acted as a developmental signal stimulating a subset of biofilm cells to revert to a motile phenotype. Transcriptomic analysis revealed that TasA stimulated the expression of a specific subset of genes whose products promote motility and repress ECM production. Spontaneous suppressor mutations that restored motility in the absence of TasA revealed that activation of the biofilm-motility switch by the two-component system CssR/CssS antagonized the TasA-mediated reversion to motility in biofilm cells. Our results suggest that although mostly sessile, biofilms retain a degree of motility by actively maintaining a motile subpopulation.

中文翻译：

---

细胞外基质蛋白 TasA 是一种发育线索，可维持枯草芽孢杆菌生物膜内的运动亚群。

在自然界中，细菌形成附着在表面上的生物膜分化的多细胞群落。在这些通常无柄的生物膜中，一部分细胞继续表达运动基因。我们发现该亚群使枯草芽孢杆菌生物膜能够在高摩擦表面上扩展。鞭毛基因的表达需要细胞外基质 (ECM) 蛋白 TasA。除了作为用于细胞附着的粘附纤维的结构作用外，TasA 还充当发育信号，刺激一部分生物膜细胞恢复为活动表型。转录组学分析显示，TasA 刺激特定基因子集的表达，其产物促进运动并抑制 ECM 产生。在没有 TasA 的情况下恢复运动的自发抑制突变表明，双组分系统 CssR/CssS 激活生物膜运动开关会拮抗 TasA 介导的生物膜细胞运动逆转。我们的结果表明，虽然大部分是无柄的，但生物膜通过积极维持运动亚群来保持一定程度的运动性。