We have constructed a restriction map for the genome of bacteriophage MX-8 from Myxococcus xanthus using the enzymes PvuII, MboI, and EcoRI. The phage genome size, as determined by restriction analysis, is 51.7 +/- 0.6 Kb. Double digestions, redigestions of isolated fragments, and crossed-contact hybridization of partial digestion products show that the restriction map is circular. Restriction analysis and Southern hybridization show that the phage DNA molecules are packaged sequentially from a concatemer starting from a specific site which we have mapped. The DNA molecules have an average terminal redundancy of approximately 8% and are circularly permuted over at least 40% of the genome.

Lipopolysaccharide is a major constituent of the cell surface of the gram-negative procaryote Myxococcus xanthus. We have purified lipopolysaccharide from M. xanthus and have shown by silver staining that the lipopolysaccharide contains a heterogeneous population of molecules which migrate as a broad lowmolecular-mass band (approximately 5 kilodaltons) and as a stepladder of about 30 higher-molecular-mass bands (15-to 70-kilodalton range). The broad band consists of lipopolysaccharide molecules with just lipid A and core regions. The stepladder bands contain lipopolysaccharide molecules with lipid A, core regions, and various numbers of 0-antigen units. Monoclonal antibodies generated against the cell surface of developing M. xanthus cells (J. S. Gill and M. Dworkin, Proc. Natl. Acad. Sci. USA 84: [4505][4506][4507][4508] 1987) were used to help characterize the lipopolysaccharide molecules. Five monoclonal antibodies bound to carbohydrate epitopes on the stepladder but not to the broad band, indicating that these monoclonal antibodies recognize carbohydrates on the 0 antigen of the lipopolysaccharide molecules. Four of these five monoclonal antibodies bound to doublet bands in the stepladder, while the other monoclonal antibody bound to singlet bands in the stepladder. One monoclonal antibody bound to a carbohydrate epitope on both the broad band and the stepladder, indicating that it bound to the core of the lipopolysaccharide.

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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). 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 TnS lipopolysaccharide 0-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) phageresistant mutants were defective in lipopolysaccharide biosynthesis. We found that many of these lipopolysaccharide 0-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.

Myxococcus xanthus YS produces particles (Mx alpha particles) that transmit genetic information between cells. Mx alpha particles might be viruses, although no host able to sustain lytic growth of Mx alpha has been discovered. The