Defects in motility and development of Myxococcus xanthus lipopolysaccharide mutants.

Five transposon Tn5 mutants of the procaryote Myxococcus xanthus had been shown previously to be defective in lipopolysaccharide biosynthesis (J. M. Fink,-M. Kalos, and J. F. Zissler, J. Bacteriol. 171:2033-2041, 1989). These mutants were studied for possible defects in gliding motility and multicellular development. Wild-type M. xanthus cells glide both as single cells and as groups of cells. We found that the Tn5 lipopolysaccharide O-antigen mutants were defective in single-cell motility but were unaltered in group motility. These mutant strains were slow to develop but eventually gave rise to normal, spore-filled fruiting bodies. We also had shown previously that 56 (ethyl methanesulfonate-induced and spontaneous) phage-resistant mutants were defective in lipopolysaccharide biosynthesis. We found that many of these lipopolysaccharide O-antigen mutants were defective in single-cell motility but were unaltered in group motility. These mutants also gave rise to normal, spore-filled fruiting bodies. We also studied several phage-resistant mutants which were lacking a side-chain carbohydrate on the lipopolysaccharide core. These mutants possessed both single-cell motility and group motility but were altered in the magnitude of gliding. These mutants were blocked early in development and could not form multicellular fruiting bodies. Several of the mutations in the developmentally aberrant strains were mapped to a single locus by using a collection of genetically linked transposons as genetic markers.