Berry R M, Turner L, Berg H C
Rowland Institute for Science, Cambridge, Massachusetts 02142, USA.
Biophys J. 1995 Jul;69(1):280-6. doi: 10.1016/S0006-3495(95)79900-3.
We used the technique of electrorotation to apply steadily increasing external torque to tethered cells of the bacterium Escherichia coli while continuously recording the speed of cell rotation. We found that the bacterial flagellar motor generates constant torque when rotating forward at low speeds and constant but considerably higher torque when rotating backward. At intermediate torques, the motor stalls. The torque-speed relationship is the same in both directional modes of switching motors. Motors forced backward usually break, either suddenly and irreversibly or progressively. Motors broken progressively rotate predominantly at integral multiples of a unitary speed during the course of both breaking and subsequent recovery, as expected if progressive breaking affects individual torque-generating units. Torque is reduced by the same factor at all speeds in partially broken motors, implying that the torque-speed relationship is a property of the individual torque-generating units.
我们运用了旋转电泳技术，对大肠杆菌的束缚细胞施加持续增加的外部扭矩，同时持续记录细胞旋转的速度。我们发现，细菌鞭毛马达在低速向前旋转时产生恒定扭矩，而在向后旋转时产生恒定但高得多的扭矩。在中等扭矩下，马达会停止运转。在两种切换模式下，扭矩 - 速度关系是相同的。被迫向后旋转的马达通常会损坏，要么突然且不可逆转地损坏，要么逐渐损坏。逐渐损坏的马达在损坏过程以及随后的恢复过程中，主要以单一速度的整数倍旋转，这正如预期的那样，如果逐渐损坏影响到单个扭矩产生单元的话。在部分损坏的马达中，所有速度下的扭矩都以相同的系数降低，这意味着扭矩 - 速度关系是单个扭矩产生单元的一种特性。
