Reversible expression of motility and flagella in Clostridium chauvoei and their relationship to virulence.

Clostridium chauvoei strain Okinawa produced spontaneous non-motile variants at an unusually high rate (approx. 10(-4) per generation) under normal conditions without mutagen. Revertants of non-motile variants were detected at a rate of approximately 10(-3). Biochemically, every variant corresponded well with the parental strain. By transmission electron microscopy, three of nine non-motile variants of strain Okinawa were found to be flagellate, while the other six were found to be aflagellate. These phenotypes were confirmed by Western blot analysis using monoclonal antibodies directed against the flagella of C. chauvoei. Moreover, the parental flagellate strain and non-motile flagellate variants were significantly more virulent in mice than non-motile, aflagellate variants. Our results demonstrated that phase variation in motility and flagellation occurs in C. chauvoei, and that the flagella are associated with the full expression of virulence.