Molecular adsorption steers bacterial swimming at the air/water interface.
Molecular adsorption steers bacterial swimming at the air/water interface.
复制标题
分子吸附引导细菌在空气/水界面游动。
DOI：
10.1016/j.bpj.2013.05.026
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发表时间：
2013
影响因子：
3.4
通讯作者：
Jay X. Tang
中科院分区：
文献类型：
--
作者：
Michael Morse;Athena Huang;Guanglai Li;M. Maxey;Jay X. Tang
栖息在地球上的微生物已经适应了水、空气、土壤等不同的环境，并且经常处于多种介质的界面。在这项研究中，我们专注于ofCaulobacter crescentus，单鞭毛细菌，在空气/水界面的行为。向前游动的新月形线虫较温暖的细胞在营养丰富的生长培养基中游动时倾向于被物理地捕获在表面，但在最低盐运动培养基中则不然。当从空中观察时，被困的细胞以略微降低的速度沿顺时针方向紧密地移动。微量的Triton X100，一种非离子表面活性剂，从这些圆形轨迹中释放被困的细胞。我们表明，通过跟踪带正电的胶体珠的界面附近的运动，生长介质中的有机分子吸附在界面处，产生高粘度的膜。因此，空气/水界面不再充当自由表面，并且向前游动的细胞被流体动力学地捕获。添加的表面活性剂有效地分配到表面，取代分子的粘性层并重建自由表面行为。这些发现有助于解释最近对大肠杆菌的类似研究，显示了依赖于媒体化学的可变手性轨迹。这两种不同的微生物物种的一致行为提供了关于微生物如何进化以科普具有挑战性的界面环境的见解。
Microbes inhabiting Earth have adapted to diverse environments of water, air, soil, and often at the interfaces of multiple media. In this study, we focus on the behavior ofCaulobacter crescentus, a singly flagellated bacterium, at the air/water interface. Forward swimmingC. crescentusswarmer cells tend to get physically trapped at the surface when swimming in nutrient-rich growth medium but not in minimal salt motility medium. Trapped cells move in tight, clockwise circles when viewed from the air with slightly reduced speed. Trace amounts of Triton X100, a nonionic surfactant, release the trapped cells from these circular trajectories. We show, by tracing the motion of positively charged colloidal beads near the interface that organic molecules in the growth medium adsorb at the interface, creating a high viscosity film. Consequently, the air/water interface no longer acts as a free surface and forward swimming cells become hydrodynamically trapped. Added surfactants efficiently partition to the surface, replacing the viscous layer of molecules and reestablishing free surface behavior. These findings help explain recent similar studies onEscherichia coli, showing trajectories of variable handedness depending on media chemistry. The consistent behavior of these two distinct microbial species provides insights on how microbes have evolved to cope with challenging interfacial environments.
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