Paster Eli, Ryu William S
Lewis-Sigler Institute for Integrative GenomicsPrinceton University, Princeton, NJ 08544, USA.
Proc Natl Acad Sci U S A. 2008 Apr 8;105(14):5373-7. doi: 10.1073/pnas.0709903105. Epub 2008 Apr 2.
Swimming Escherichia coli responds to changes in temperature by modifying its motor behavior. Previous studies using populations of cells have shown that E. coli accumulate in spatial thermal gradients, but these experiments did not cleanly separate thermal responses from chemotactic responses. Here we have isolated the thermal response by studying the behavior of single, tethered cells. The motor output of cells grown at 33 degrees C was measured at constant temperature, from 10 degrees to 40 degrees C, and in response to small, impulsive increases in temperature, from 23 degrees to 43 degrees C. The thermal impulse response at temperatures < 31 degrees C is similar to the chemotactic impulse response: Both follow a similar time course, share the same directionality, and show biphasic characteristics. At temperatures > 31 degrees C, some cells show an inverted response, switching from warm- to cold-seeking behavior. The fraction of inverted responses increases nonlinearly with temperature, switching steeply at the preferred temperature of 37 degrees C.
游动的大肠杆菌通过改变其运动行为来响应温度变化。此前使用细胞群体进行的研究表明，大肠杆菌会在空间温度梯度中聚集，但这些实验并未将热响应与趋化响应清晰地分离。在此，我们通过研究单个固定细胞的行为分离出了热响应。在33摄氏度下生长的细胞的运动输出在恒定温度下（从10摄氏度到40摄氏度）以及响应温度的小幅脉冲式升高（从23摄氏度到43摄氏度）时进行了测量。在温度<31摄氏度时的热脉冲响应类似于趋化脉冲响应：两者都遵循相似的时间进程，具有相同的方向性，并呈现双相特征。在温度>31摄氏度时，一些细胞表现出反向响应，从向暖行为转变为向冷行为。反向响应的比例随温度非线性增加，在37摄氏度的偏好温度处急剧转变。
