Sorbonne Université, Centre National de la Recherche Scientifique, Laboratoire Jean Perrin, LJP, Paris, 75005, France.
Environ Microbiol. 2023 Aug;25(8):1451-1464. doi: 10.1111/1462-2920.16373. Epub 2023 Mar 25.
Pseudomonas aeruginosa makes and secretes massive amounts of rhamnolipid surfactants that enable swarming motility over biogel surfaces. But how these rhamnolipids interact with biogels to assist swarming remains unclear. Here, I use a combination of optical techniques across scales and genetically engineered strains to demonstrate that rhamnolipids can induce agar gel swelling over distances >10,000× the body size of an individual cell. The swelling front is on the micrometric scale and is easily visible using shadowgraphy. Rhamnolipid transport is not restricted to the surface of the gel but occurs through the whole thickness of the plate and, consequently, the spreading dynamics depend on the local thickness. Surprisingly, rhamnolipids can cross the whole gel and induce swelling on the opposite side of a two-face Petri dish. The swelling front delimits an area where the mechanical properties of the surface properties are modified: water wets the surface more easily, which increases the motility of individual bacteria and enables collective motility. A genetically engineered mutant unable to secrete rhamnolipids (ΔrhlA), and therefore unable to swarm, is rescued from afar with rhamnolipids produced by a remote colony. These results exemplify the remarkable capacity of bacteria to change the physical environment around them and its ecological consequences.
铜绿假单胞菌产生并分泌大量鼠李糖脂表面活性剂，使它们能够在生物凝胶表面进行群集运动。但是，这些鼠李糖脂如何与生物凝胶相互作用以帮助群集运动尚不清楚。在这里，我使用跨尺度的光学技术和经过基因工程改造的菌株组合，证明鼠李糖脂可以诱导琼脂凝胶在超过单个细胞体大小 10000 倍以上的距离上膨胀。膨胀前沿处于微米级尺度，使用阴影摄影术很容易观察到。鼠李糖脂的运输不仅限于凝胶表面，而是通过整个平板的厚度进行的，因此，扩展动力学取决于局部厚度。令人惊讶的是，鼠李糖脂可以穿过整个凝胶并在双面孔氏培养皿的另一侧诱导凝胶膨胀。膨胀前沿限定了一个区域，该区域的表面特性的机械性能发生了改变：水更容易润湿表面，从而增加了单个细菌的运动能力，并使群体运动成为可能。一个无法分泌鼠李糖脂的基因工程突变体（ΔrhlA），因此无法进行群集运动，通过远程殖民地产生的鼠李糖脂从远处得到拯救。这些结果体现了细菌改变周围物理环境及其生态后果的非凡能力。
