Key Laboratory of Subtropical Agriculture and Environment, Ministry of Agriculture, Huazhong Agricultural University, Wuhan, China.
J Contam Hydrol. 2011 Sep 25;126(1-2):113-20. doi: 10.1016/j.jconhyd.2011.08.001. Epub 2011 Aug 10.
To examine and quantify the effects of glass beads and chemoattractant on bacterial motility in granular media, we examined the motile behavior of P. aeruginosa in a saturated granular medium and quantified the effects of glass beads and the presence of a chemoattractant. By recording individual cell trajectories in microfluidic channels under a high-speed confocal microscope, we directly measured the cell's run direction and corresponding run-length, speed and turn angle. Bacterial run speed increased in the presence of chemoattractant in both aqueous and granular media. But it decreased in glass-beads compared to in aqueous media due to the restricted pore geometry and interactions between bacteria and grain surfaces. Notably, the relatively higher frequency distribution at turn angles of 170° decreased dramatically, while the smaller peak at 70° increased and became dominant on a bimodal distribution, showing more bacteria changed directions at smaller turn angles rather than reverse their swimming directions. Additionally, the presence of glass beads also decreased the chemotactic velocity and random motility by similar proportions due to the restrictive geometry and the interactions between bacteria and glass beads surface. Our study indicates that the swimming parameters measured from aqueous media cannot be directly adopted in models for predicting bacteria travel in granular media.
为了研究玻璃珠和趋化剂对颗粒介质中细菌运动性的影响，我们研究了铜绿假单胞菌在饱和颗粒介质中的运动行为，并量化了玻璃珠和趋化剂的存在对细菌运动性的影响。通过在高速共聚焦显微镜下的微流道中记录单个细胞轨迹，我们直接测量了细胞的运行方向和相应的运行长度、速度和转弯角度。在水相和颗粒相介质中，存在趋化剂时，细菌的运行速度均增加。但由于受限的孔几何形状和细菌与颗粒表面之间的相互作用，细菌在玻璃珠中的运行速度比在水相介质中要低。值得注意的是，转弯角度为 170°的相对较高的频率分布显著降低，而转弯角度为 70°的较小峰值增加并在双峰分布中占主导地位，表明更多的细菌在较小的转弯角度改变方向，而不是反向游动。此外，由于受限的几何形状和细菌与玻璃珠表面之间的相互作用，玻璃珠的存在也使趋化运动速度和随机运动性以相似的比例降低。我们的研究表明，从水相介质中测量的游动参数不能直接用于预测细菌在颗粒介质中迁移的模型。
