Department of Physics, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea.
Department of Biological Sciences, Ulsan National Institute of Science and Technology, Ulsan, Republic of Korea.
Soft Matter. 2024 Sep 18;20(36):7313-7320. doi: 10.1039/d4sm00766b.
In nature, bacteria often swim in complex fluids, but our understanding of the interactions between bacteria and complex surroundings is still evolving. In this work, rod-like swims in a quasi-2D environment with aqueous liquid-liquid interfaces, , the isotropic-nematic coexistence phase of an aqueous chromonic liquid crystal. Focusing on the bacteria motion near and at the liquid-liquid interfaces, we collect and quantify bacterial trajectories ranging across the isotropic to the nematic phase. Despite its small magnitude, the interfacial tension of the order of 10 μN m at the isotropic-nematic interface justifies our observations that bacteria swimming more perpendicular to the interface have a higher probability of crossing the interface. Our force-balance model, considering the interfacial tension, further predicts how the length and speed of the bacteria affect their crossing behaviors. Investigating how a phase change affects bacterial motion, we also find, as soon as the bacteria cross the interface and enter the nematic phase, they wiggle less, but faster, and that this occurs as the flagellar bundles aggregate within the nematic phase. Given the ubiquity of multi-phases in biological environments, our findings will help to understand active transport across various phases.
在自然界中，细菌经常在复杂的流体中游动，但我们对细菌与复杂环境之间的相互作用的理解仍在不断发展。在这项工作中，棒状细菌在具有水-水相界面的准二维环境中游泳， ，这是各向同性-向列相共存相的水相胆甾液晶。我们专注于细菌在接近和位于液-液界面附近的运动，收集并量化了跨越各向同性相到向列相的细菌轨迹。尽管界面张力的大小相对较小，约为 10 μN m，但在各向同性-向列相界面处的界面张力使得我们可以观察到，细菌在更垂直于界面的方向游动时，穿过界面的概率更高。我们的力平衡模型，考虑了界面张力，进一步预测了细菌的长度和速度如何影响它们的穿越行为。研究相变化如何影响细菌运动，我们还发现，一旦细菌穿过界面进入向列相，它们的摆动就会减少，但速度会加快，并且这种情况发生在鞭毛束在向列相中聚集时。鉴于多相在生物环境中的普遍性，我们的发现将有助于理解各种相之间的主动运输。
