Myxococcus xanthus dif genes are required for biogenesis of cell surface fibrils essential for social gliding motility

Myxococcus xanthus social (S) gliding motility has been previously reported by us to require the chemotaxis homologues encoded by the dif genes. In ad dition, two cell surface structures, type IV pili and extracellular matrix fibrils, are also critical to M. xanthus S motility, We have demonstrated h ere that M. xanthus dif genes are required for the biogenesis of fibrils bu t not for that of type IV pili, Furthermore, the developmental defects of d if mutants can be partially rescued by the addition of isolated fibril mate rials. Along with the chemotaxis genes of various swarming bacteria and the pilGHIJ genes of the twitching bacterium Pseudomonas aeruginosa, the M. xa nthus dif genes belong to a unique class of bacterial chemotaxis genes or h omologues implicated in the biogenesis of structures required for bacterial surface locomotion. Genetic studies indicate that the dif genes are linked to the M. xanthus nsp region, a locus known to be crucial for M. xanthus f ibril biogenesis and S gliding.