TEMPORAL COMPARISONS IN BACTERIAL CHEMOTAXIS
TEMPORAL COMPARISONS IN BACTERIAL CHEMOTAXIS
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DOI：
10.1073/pnas.83.23.8987
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发表时间：
1986-12-01
影响因子：
11.1
通讯作者：
BERG, HC
中科院分区：
文献类型：
--
作者：
SEGALL, JE;BLOCK, SM;BERG, HC
大肠杆菌栓系细胞对脉冲、阶跃、指数斜坡或指数正弦波刺激的反应是内部一致的，只要考虑阈值的非线性效应。该结果证实，暴露于生理范围内的刺激的野生型细胞进行了延伸到过去4秒的短期时间比较：过去的一秒被赋予正权重，前3秒被赋予负权重，并且细胞对差异做出响应。cheRcheB突变体（甲基化和去甲基化缺陷）以类似于野生型的方式对过去的一秒进行加权，但它们不进行短期时间比较。当暴露于离子电渗递送的小步长时，它们在长达12秒的时间内无法适应;当暴露于流动池中的较长步长时，它们部分适应，但衰减时间> 30秒。cheZ突变体使用延伸到过去至少40秒的加权。趋化系统的增益很大：一个受体分子占据的变化产生显著的响应。
Response of tethered cells of Escherichia coli to impulse, step, exponential-ramp or exponentiated sine-wave stimuli are internally consistent, provided that allowance is made for the nonlinear effect of thresholds. This result confirms that wild-type cells exposed to stimuli in the physiological range make short-term temporal comparisons extending 4 sec into the past: the past second is given a positive weighting, the previous 3 sec are given a negative weighting, and the cells respond to the difference. cheRcheB mutants (defective in methylation and demethylation) weight the past second in a manner similar to the wild type, but they do not make short-term temporal comparisons. When exposed to small steps delivered iontophoretically, they fail to adapt over periods of up to 12 sec; when exposed to longer steps in a flow cell, they partially adapt, but with a decay time of > 30 sec. cheZ mutants use a weighting that extends at least 40 sec into the past. The gain of the chemotactic system is large: the change in occupancy of one receptor molecule produces a significant response.