在E.大肠杆菌鞭毛马达
Stochastic model for the CheY-P molarity in the neighbourhood of E. coli flagella motors
摘要：
大肠杆菌是研究交替进行奔跑和翻滚的围毛型肠道细菌的原型。细菌由于其鞭毛束的逆时针（CCW）旋转而向前移动，并且当至少一个鞭毛顺时针（CW）旋转时，细菌会从鞭毛束中离开。鞭毛被钩在纳米直径的分子旋转马达上，能够在CCW和CW旋转之间进行转换，持续时间长达百分之一秒。与此同时，鞭毛在十分之一到十秒的时间内移动或旋转细菌的身体。我们假设CCW和CW旋转之间的过渡只发生在两个阈值的存在下的Chey-P摩尔浓度的波动，并且否决规则选择运行或翻滚运动。我们目前Langevin方程的Chey-P摩尔浓度在附近的每个分子马达。该模型允许获得运行或翻滚时间分布作为递减指数的线性组合，其是在分子马达附近的Chey-P的稳定摩尔浓度的函数，其拟合实验数据。反过来，如果内部信号系统是未受刺激的，我们表明，运行时分布达到幂律行为，自组织系统的一个特征，在一定的时间范围内，之后，指数截止。此外，我们的模型解释了没有任何拟合参数的鞭毛电机的超灵敏度作为一个函数的Chey-P摩尔浓度的稳定状态。此外，我们发现，翻滚的偏见peritrichous细菌有一个类似的S形形状的CW偏置，虽然转移到较低的浓度时，鞭毛数量的增加。因此，鞭毛数量的增加允许每个马达的较低操作值，从而增加趋化途径的扩增和稳健性。
英文摘要：
E.coli serves as prototype for the study of peritrichous enteric bacteria that perform runs and tumbles alternately. Bacteria run forward as a result of the counterclockwise (CCW) rotation of their flagella bundle and perform tumbles when at least one of their flagella rotates clockwise (CW), moving away from the bundle. The flagella are hooked to molecular rotary motors of nanometric diameter able to make transitions between CCW and CW rotations that last up to one hundredth of a second. At the same time, flagella move or rotate the bacteria's body microscopically during lapses that range between a tenth and ten seconds. We assume that the transitions between CCW and CW rotations occur solely by fluctuations of CheY-P molarity in the presence of two threshold values, and that a veto rule selects the run or tumble motions. We present Langevin eqs for the CheY-P molarity in the vicinity of each molecular motor. This model allows to obtain the run- or tumble-time distribution as a linear combination of decreasing exponentials that is a function of the steady molarity of CheY-P in the neighbourhood of the molecular motor, which fits experimental data. In turn, if the internal signaling system is unstimulated, we show that the runtime distributions reach power-law behaviour, a characteristic of self-organized systems, in some time range and, afterwards, exponential cutoff. In addition, our model explains without any fitting parameters the ultrasensitivity of the flagella motors as a function of the steady state of CheY-P molarity. In addition, we show that the tumble bias for peritrichous bacterium has a similar sigmoid-shape to the CW bias, although shifted to lower concentrations when the flagella number increases. Thus, the increment in the flagella number allows lower operational values for each motor increasing amplification and robustness of the chemotatic pathway.
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