Gliding motility mutants of Myxococcus xanthus

Two gliding motility mutants of Myxococcus xanthus are described. The semimotile mutant (SM) originated by high-frequency segregation from the motile FB(t) strain. Segregation was enhanced by acridine dye treatment. SM cells glide only when apposed to other cells in a swarm. The nonmotile strain (NM) originated by mutation from SM. NM cells neither glide individually nor cooperatively. FB(t), SM, and NM are indistinguishable with respect to fine structure, vegetative growth rate, glycerol-induced microcyst formation, spheroplasting, bacteriophage sensitivity, and responses to light. The motility mutants are more resistant to penicillin and more sensitive to actinomycin D than is the gliding wild type. The NM mutant is also a morphogenetic mutant; it is unable to form fruiting bodies.