标题： 行波吸引物环境中细菌的趋化性 显示英文标题

标题： Bacterial Chemotaxis in a Traveling Wave Attractant Environment

摘要： 我们研究了单个细胞大肠杆菌在时空变化的吸引物环境中的趋化性。通过将吸引物浓度建模为行进的正弦波形式，我们在模拟中测量了细胞在不同传播速度的吸引物波下的趋化漂移速度。我们发现了一种高度非平凡的依赖关系，其中趋化漂移速度会改变符号，并且显示出多个峰值。对于移动缓慢的吸引物波，漂移速度为负值，即漂移运动的方向与波传播方向相反。随着波速增加，漂移速度出现一个负峰，然后改变符号，达到一个正值峰，最后当波速过快以至于细胞无法响应时变为零。我们从细胞在其沿传播方向和反方向运行期间感知到的吸引物梯度差异来解释这种丰富的行为。特别是，当细胞与波同向移动时，当波速与运行速度匹配时，细胞相对于波的相对速度变为零，在此极限情况下，细胞能够“搭乘”波并在这些运行中经历不到浓度梯度。相反，对于反方向运行，不存在这种效应，有效梯度随波速单调增加。我们使用详细的定量测量展示了这种差异如何导致上述趋化漂移速度的反直觉行为。 显示英文摘要

摘要： We study single cell E.coli chemotaxis in a spatio-temporally varying attractant environment. Modeling the attractant concentration in the form of a traveling sine wave, we measure in our simulations, the chemotactic drift velocity of the cell for different propagation speed of the attractant wave. We find a highly non-trivial dependence where the chemotactic drift velocity changes sign, and also shows multiple peaks. For slowly moving attractant wave, drift velocity is negative, i.e. the drift motion is directed opposite to wave propagation. As the wave speed increases, drift velocity shows a negative peak, then changes sign, reaches a positive peak and finally becomes zero when the wave moves too fast for the cell to respond. We explain this rich behavior from the difference in attractant gradient perceived by the cell during its run along the propagation direction and opposite to it. In particular, when the cell moves in the same direction as the wave, the relative velocity of the cell with respect to the wave becomes zero when the wave speed matches the run speed. In this limit, the cell is able to ride the wave and experiences no concentration gradient during these runs. On the contrary, for runs in the opposite direction, no such effect is present and the effective gradient increases monotonically with the wave speed. We show, using detailed quantitative measurements, how this difference gives rise to the counter-intuitive behavior of chemotactic drift velocity described above.