运 轮辐8的总 △IE 移位度 ella. to 3×29m Dr the of mew Then 纤毛外 聯及 所附突起 tastant 外二联体 及所射 cerium on of 鞭毛从基部到頂壤不断地波瀆弌运动,使 细胞向对侧推进b纤毛的拍打式运动。拍 打的起劲和拨复可以不处于一个平面上,大 头示厕围液体运动的方向c弯曲纤毛的 基部,图示在纤毛每一侧轮辐进行性的移位, 表明二联体戗此间的滑动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