Characterization of polar-flagellar-length mutants in Vibrio alginolyticus

Vibrio alginolyticus has two types of flagella, polar (Pof) and lateral (Laf). From a Laf-defective mutant (Pof⁺Laf^-), polar-flagellar-length mutants which have short Pof and long Pof were isolated. The mean lengths of the helical axis in wild-type, short and long Pof were 5.5.0.9 μm, 2.5.0.6 μm and 11.2.3.6 μm, respectively. The swimming speeds of the short- and long-Pof mutants were slower than that of the wild-type strain. The relationship between swimming speed and flagellar length in a population of mutant cells was examined. In the short-Pof mutant, the decrease of swimming speed seemed to be derived from the decrease in flagellar length. In the long-Pof mutant, there was almost no correlation between swimming speed and flagellar length, and the slow swimming was explained by the helical shape of the flagella, whose pitch and radius were 1.4 μm and 0.062 μm, respectively, whereas those of the wild-type flagella were 1.5 μm and 0.16 μm. The relative amounts of the various molecular components of the long Pof were different from those of the wild-type or the short Pof. This seems to be the reason for the difference in flagellar shape and length, though the mutation may be pleiotropic and affect flagellar function or regulation.