Bacteria exploit a polymorphic instability of the flagellar filament to escape from traps
Bacteria exploit a polymorphic instability of the flagellar filament to escape from traps
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DOI：
10.1073/pnas.1701644114
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发表时间：
2017-06-13
影响因子：
11.1
通讯作者：
Thormann, Kai M.
中科院分区：
文献类型：
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作者：
Kuehn, Marco J.;Schmidt, Felix K.;Thormann, Kai M.
许多细菌通过旋转的单极螺旋鞭毛游动。根据旋转的方向，它们可以向前或向后游泳，并改变方向以沿着化学梯度移动，但也可以在土壤，沉积物或粘液中航行。当它们陷入困境时，它们自然会试图退出，但它们也可以诉诸一种完全不同的鞭毛模式，我们在这里发现了这一点。使用高速显微镜，我们监测的游泳行为的monolarly鞭毛种希瓦氏菌腐败与荧光标记的鞭毛丝在琼脂糖-玻璃界面。我们表明，当一个细胞卡住，极鞭毛丝执行多态性变化成螺旋状的形式，在一个螺旋状的方式包裹在细胞体，使细胞逃脱的螺丝一样向后运动。显微镜和建模表明，这种传播模式是由鞭毛的旋转和施加的扭矩逆转下的不稳定性触发的。这种转换是可逆的，已经逃离陷阱的细菌可以通过另一个电机方向的逆转返回到正常的游泳模式。螺旋型鞭毛的安排，使一个独特的模式的传播，并考虑到大量的极性鞭毛细菌，我们希望它是一个常见的和广泛的逃生或运动模式在复杂和结构化的环境。
Many bacterial species swim by rotating single polar helical flagella. Depending on the direction of rotation, they can swim forward or backward and change directions to move along chemical gradients but also to navigate their obstructed natural environment in soils, sediments, or mucus. When they get stuck, they naturally try to back out, but they can also resort to a radically different flagellar mode, which we discovered here. Using high-speed microscopy, we monitored the swimming behavior of the monopolarly flagellated species Shewanella putrefaciens with fluorescently labeled flagellar filaments at an agarose-glass interface. We show that, when a cell gets stuck, the polar flagellar filament executes a polymorphic change into a spiral-like form that wraps around the cell body in a spiral-like fashion and enables the cell to escape by a screw-like backward motion. Microscopy and modeling suggest that this propagation mode is triggered by an instability of the flagellum under reversal of the rotation and the applied torque. The switch is reversible and bacteria that have escaped the trap can return to their normal swimming mode by another reversal of motor direction. The screw-type flagellar arrangement enables a unique mode of propagation and, given the large number of polarly flagellated bacteria, we expect it to be a common and widespread escape or motility mode in complex and structured environments.