Growth of Variants of Myxococcus virescens

Some observations on variant strains of Myxococcus virescens B2 with special emphasis on characteristics associated with the ability to grow in dispersion are reported. The isolated strains were divided into two major classes according to their mode of growth in shaken and static liquid cultures based on casitone and casamino acids media. Strains growing in dispersion were designated D⁺-strains and those growing in aggregates or as films, D^?-strains. Colony morphology, cell morphology, growth in liquid and on solid medium and morphogenesis were compared. The ability to grow in dispersion shown by D⁺-strains seemed to be associated with a smooth colony on casitone agar, inability to form typical fruiting bodies and a low linear growth rate of colonies on solid medium as compared with the D^?-strains. In contrast D^?-strains produced rough colonies on casitone agar, were able to fruit and evidently formed an adhesive slime in the form of fibrils extending from the cell surface. It is suggested that the observed differences depend on different envelopes of the cells in the two classes.