Requirement of the fixed end for spontaneous beating in flagella.

It is well known that any part of a flagellum has the ability to bend. However, it is not clearly understood how flagella generate successive bending waves spontaneously. Some micromanipulation experiments have suggested that the base of the flagellum is required. By contrast, spontaneous bending waves could be generated in computer simulation work if the microtubules were tied together at one end. We hypothesized that the basal structure of flagella can only act as a tied end when the outer doublet microtubules are tightly bound together so as not to slide. We developed a new technique for introducing local inhibition at any position on the demembranated and reactivated flagellum. The flagellum maintained spontaneous beating when the local inhibition was introduced at any position on it. In addition, spontaneous beating occurred without the basal body when an artificial fixed region was introduced to the flagellum. We conclude that the axoneme, a bundle of microtubules, requires the fixed end for spontaneous beating.