Gliding Motility of Myxococcus xanthus

Myxococcus xanthus is one of the diverse bacteria that display gliding motility, involving two mechanisms, called adventurous (A) and social (S) gliding motility. The genetic and phenotypic analysis of mutants defective in gliding motility has shown that gliding motility is more complex than flagellum-dependent motility. The first molecular insights about the mechanisms of gliding motility were gleaned from the results of genetic studies performed by Hodgkin and Kaiser, who used chemical mutagens to generate mutations that affected gliding. The phenotypes of gliding mutants can be measured in terms of the differences in their velocities of gliding. The more detailed molecular genetic analysis of the two mechanisms of gliding motility in M. xanthus has been facilitated by the use of transposon mutagenesis. M. xanthus cells that have a functional A gliding system are able to move as isolated cells on a solid surface. The majority of mutations that abolish S motility affect the production of type IV pili (TFP), the exopolysaccharide (EPS) component of fibrils, or the lipopolysaccharide (LPS) moiety of O-antigen. The function of EPS in social motility has been elucidated by phenotypic analysis of mutants of M. xanthus lacking EPS, a secreted polymer comprised primarily of N-acetylglucosamine (GlcNAc) and glucosamine (GlcN). M. xanthus has a complex life cycle. In the presence of adequate nutrients, the cells undergo vegetative growth and divide, but when the cells are starved of nutrients, they aggregate and form fruiting bodies containing myxospores.