运 Jww. cellsaliue co 轮幅8的总 移位度 lla, to Drec the of mevement e. Then 纤毛外展 中央聊及 所附突起 tastant 外二联体 cerium 及所轮辐 lon of a鞭毛从基部到頂端不断地波滚式运动,使 细胞向对侧摧进b纤毛的拍打式运动。拍 打的起动和恢复可以不处于一个平面上,大 筲头示周围液体运动的方向c李曲纤毛的 基部,图示在纤毛每一侧轮辐进行性的移位 者明二联体後此问的滑A motile E. coli propels itself from place to place by rotating its flagella. To move forward, the flagella rotate counterclockwise and the organism "swims". But when flagellar rotation abruptly changes to clockwise, the bacterium "tumbles" in place and seems incapable of going anywhere. Then the bacterium begins swimming again in some new, random direction. Swimming is more frequent as the bacterium approaches a chemoattractant (food). Tumbling, hence direction change, is more frequent as the bacterium moves away from the chemoattractant. So it is a complex combination of swimming and tumbling that keeps them in areas of higher food concentrations. • 鞭 毛 运 动