Dienerowitz Maria, Cowan Laura V, Gibson Graham M, Hay Rebecca, Padgett Miles J, Phoenix Vernon R
SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow, G12 8QQ, UK,
Curr Microbiol. 2014 Nov;69(5):669-74. doi: 10.1007/s00284-014-0641-5. Epub 2014 Jun 26.
Aggregation of bacteria plays a key role in the formation of many biofilms. The critical first step is cell-cell approach, and yet the ability of bacteria to control the likelihood of aggregation during this primary phase is unknown. Here, we use optical tweezers to measure the force between isolated Bacillus subtilis cells during approach. As we move the bacteria towards each other, cell motility (bacterial swimming) initiates the generation of repulsive forces at bacterial separations of ~3 μm. Moreover, the motile response displays spatial sensitivity with greater cell-cell repulsion evident as inter-bacterial distances decrease. To examine the environmental influence on the inter-bacterial forces, we perform the experiment with bacteria suspended in Tryptic Soy Broth, NaCl solution and deionised water. Our experiments demonstrate that repulsive forces are strongest in systems that inhibit biofilm formation (Tryptic Soy Broth), while attractive forces are weak and rare, even in systems where biofilms develop (NaCl solution). These results reveal that bacteria are able to control the likelihood of aggregation during the approach phase through a discretely modulated motile response. Clearly, the force-generating motility we observe during approach promotes biofilm prevention, rather than biofilm formation.
细菌聚集在许多生物膜的形成过程中起着关键作用。关键的第一步是细胞间靠近，然而细菌在这个初始阶段控制聚集可能性的能力尚不清楚。在这里，我们使用光镊来测量靠近过程中分离的枯草芽孢杆菌细胞之间的力。当我们将细菌相互靠近时，细胞运动性（细菌游动）在细菌间距约为3微米时开始产生排斥力。此外，运动反应表现出空间敏感性，随着细菌间距离减小，细胞间排斥力更明显。为了研究环境对细菌间力的影响，我们用悬浮在胰蛋白胨大豆肉汤、氯化钠溶液和去离子水中的细菌进行实验。我们的实验表明，排斥力在抑制生物膜形成的系统（胰蛋白胨大豆肉汤）中最强，而吸引力即使在生物膜形成的系统（氯化钠溶液）中也很微弱且罕见。这些结果表明，细菌能够通过离散调节的运动反应来控制靠近阶段的聚集可能性。显然，我们在靠近过程中观察到的产生力的运动性促进了生物膜的预防，而不是生物膜的形成。
