Sretenovic Simon, Stojković Biljana, Dogsa Iztok, Kostanjšek Rok, Poberaj Igor, Stopar David
Biotechnical Faculty, University of Ljubljana, Vecna pot 111, Ljubljana, 1000, Slovenia.
Medical Faculty, Institute of Biophysics, University of Ljubljana, Vrazov trg 2, Ljubljana, 1000, Slovenia.
Nat Commun. 2017 Aug 9;8(1):213. doi: 10.1038/s41467-017-00295-z.
It is generally accepted that planktonic bacteria in dilute suspensions are not mechanically coupled and do not show correlated motion. The mechanical coupling of cells is a trait that develops upon transition into a biofilm, a microbial community of self-aggregated bacterial cells. Here we employ optical tweezers to show that bacteria in dilute suspensions are mechanically coupled and show long-range correlated motion. The strength of the coupling increases with the growth of liquid bacterial culture. The matrix responsible for the mechanical coupling is composed of cell debris and extracellular polymer material. The fragile network connecting cells behaves as viscoelastic liquid of entangled extracellular polymers. Our findings point to physical connections between bacteria in dilute bacterial suspensions that may provide a mechanistic framework for understanding of biofilm formation, osmotic flow of nutrients, diffusion of signal molecules in quorum sensing, or different efficacy of antibiotic treatments at low and high bacterial densities.Planktonic bacteria are untethered to surfaces or to each other, and thus are expected to move independently when at low cell densities. Here Sretenovic et al. show, using optical tweezers, that bacteria in dilute suspensions are mechanically coupled and show long-range correlated motion.
一般认为，稀悬浮液中的浮游细菌没有机械耦合，也不显示相关运动。细胞的机械耦合是在转变为生物膜（一种由自聚集细菌细胞组成的微生物群落）时出现的一种特性。在这里，我们使用光镊来表明稀悬浮液中的细菌是机械耦合的，并显示出长程相关运动。耦合强度随着液体细菌培养物的生长而增加。负责机械耦合的基质由细胞碎片和细胞外聚合物材料组成。连接细胞的脆弱网络表现为缠结的细胞外聚合物的粘弹性液体。我们的发现指出了稀细菌悬浮液中细菌之间的物理连接，这可能为理解生物膜形成、营养物质的渗透流、群体感应中信号分子的扩散或低细菌密度和高细菌密度下抗生素治疗的不同效果提供一个机制框架。浮游细菌不附着于表面或彼此，因此预计在低细胞密度时会独立移动。在这里，斯特雷诺维奇等人使用光镊表明，稀悬浮液中的细菌是机械耦合的，并显示出长程相关运动。
