Brown D A, Berg H C
Proc Natl Acad Sci U S A. 1974 Apr;71(4):1388-92. doi: 10.1073/pnas.71.4.1388.
We used the tracking microscope to study the chemotactic responses of E. coli to temporal gradients of L-glutamate generated in isotropic solutions by the action of the enzyme alanine aminotransferase. Positive gradients suppress directional changes which occur spontaneously in the absence of a stimulus. Negative gradients have little effect. The data can be fit with a model in which the suppression is proportional to the time rate of change of the fractional amount of chemoreceptor bound. The model accounts for the behavior of individual cells and populations of cells in spatial gradients. A computer simulation of the motion in spatial gradients indicates that if the bacteria have a "memory," its decay time cannot be much longer than a few seconds. The relationship between the responses observed in these experiments and in experiments in which solutions of an attractant at different concentrations are mixed is discussed.
我们使用追踪显微镜研究了大肠杆菌对丙氨酸转氨酶作用下在各向同性溶液中产生的L-谷氨酸时间梯度的趋化反应。正梯度抑制了在无刺激情况下自发发生的方向变化。负梯度影响很小。这些数据可以用一个模型来拟合，其中抑制作用与化学感受器结合分数的时间变化率成正比。该模型解释了单个细胞和细胞群体在空间梯度中的行为。对空间梯度中运动的计算机模拟表明，如果细菌有“记忆”，其衰减时间不会比几秒长得多。本文还讨论了这些实验中观察到的反应与不同浓度引诱剂溶液混合实验中观察到的反应之间的关系。
