Flagella enable bacteria to actively spread within the environment. A number of species possess two separate flagellar systems, where in most cases a primary polar flagellar system is supported by distinct secondary lateral flagella under appropriate conditions. Using functional fluorescence tagging on one of these species, Shewanella putrefaciens, as a model system, we explored how two different flagellar systems can exhibit efficient joint function. The S. putrefaciens secondary flagellar filaments are composed as a mixture of two highly homologous non-glycosylated flagellins, FlaA₂ and FlaB₂. Both are solely sufficient to form a functional filament, however, full spreading motility through soft agar requires both flagellins. During swimming, lateral flagella emerge from the cell surface at angles between 30° and 50°, and only filaments located close to the cell pole may form a bundle. Upon a directional shift from forward to backward swimming initiated by the main polar flagellum, the secondary filaments flip over and thus support propulsion into either direction. Lateral flagella do not inhibit the wrapping of the polar flagellum around the cell body at high load. Accordingly, screw thread-like motility mediated by the primary flagellum and activity of lateral flagella cumulatively supports spreading through constricted environments such as polysaccharide matrices.

中文翻译：

---

极地鞭毛包裹和侧鞭毛共同促进了 Shewanella putrefaciens 的环境传播

鞭毛使细菌能够在环境中积极传播。许多物种拥有两个独立的鞭毛系统，其中在大多数情况下，初级极地鞭毛系统在适当条件下由不同的次级侧鞭毛支持。使用对这些物种之一的功能性荧光标记，Shewanella putrefaciens作为模型系统，我们探索了两种不同的鞭毛系统如何表现出有效的联合功能。S。_ 腐败菌次级鞭毛丝由两种高度同源的非糖基化鞭毛蛋白 FlaA ₂和 FlaB _{2的混合物组成}. 两者都足以形成功能性细丝，但是，通过软琼脂的完全传播运动需要两种鞭毛蛋白。在游动过程中，侧鞭毛以 30° 和 50° 之间的角度从细胞表面出现，只有靠近细胞极的细丝才能形成束。在由主极鞭毛发起的从向前游泳到向后游泳的方向转变时，次级丝翻转并因此支持向任一方向的推进。在高负荷下，侧鞭毛不会抑制极鞭毛在细胞体周围的包裹。因此，由初级鞭毛介导的螺纹状运动和侧鞭毛的活动累积支持通过收缩环境（如多糖基质）传播。