Turner Linda, Ping Liam, Neubauer Marianna, Berg Howard C
Rowland Institute at Harvard, Harvard University, Cambridge, Massachusetts.
Ecmictics Biotechnology, Markham, Ontario, Canada.
Biophys J. 2016 Aug 9;111(3):630-639. doi: 10.1016/j.bpj.2016.05.053.
A complete description of the swimming behavior of a bacterium requires measurement of the displacement and orientation of the cell body together with a description of the movement of the flagella. We rebuilt a tracking microscope so that we could visualize flagellar filaments of tracked cells by fluorescence. We studied Escherichia coli (cells of various lengths, including swarm cells), Bacillus subtilis (wild-type and a mutant with fewer flagella), and a motile Streptococcus (now Enterococcus). The run-and-tumble statistics were nearly the same regardless of cell shape, length, and flagellation; however, swarm cells rarely tumbled, and cells of Enterococcus tended to swim in loops when moving slowly. There were events in which filaments underwent polymorphic transformations but remained in bundles, leading to small deflections in direction of travel. Tumble speeds were ∼2/3 as large as run speeds, and the rates of change of swimming direction while running or tumbling were smaller when cells swam more rapidly. If a smaller fraction of filaments were involved in tumbles, the tumble intervals were shorter and the angles between runs were smaller.
对细菌游泳行为的完整描述需要测量细胞体的位移和方向，以及对鞭毛运动的描述。我们重建了一台跟踪显微镜，以便通过荧光可视化被跟踪细胞的鞭毛丝。我们研究了大肠杆菌（各种长度的细胞，包括群体细胞）、枯草芽孢杆菌（野生型和鞭毛较少的突变体）以及一种运动性链球菌（现称肠球菌）。无论细胞形状、长度和鞭毛情况如何，游动和翻滚的统计数据几乎相同；然而，群体细胞很少翻滚，肠球菌细胞在缓慢移动时倾向于呈环状游动。存在鞭毛丝发生多态转变但仍保持成束的情况，这会导致行进方向出现小的偏差。翻滚速度约为游动速度的2/3，当细胞游动速度更快时，游动或翻滚时游泳方向的变化率更小。如果参与翻滚的鞭毛丝比例较小，翻滚间隔会更短，游动之间的角度也更小。
