Penicillin and D-Alanyl-D-alanine Accelerate Spore Formation of Myxococcus xanthus Subcultured Cells

In repetitive subcultures of Myxococcus xanthus cells, addition of penicillin to the developmental medium accelerated the appearance of the fruiting bodies and spore formation. During development of M. xanthus, DD-carboxypeptidase, which functions in the regulation of the level of cross-linkage, was also induced by penicillin. When D-alanyl-D-alanine, the structure of which is similar to the β-lactam structure of penicillin, was added to the developmental medium, 0.3 to 0.6 mM D-alanyl-D-alanine accelerated spore formation strongly. The activity of D-alanyl-D-alanine ligase, which synthesizes D-alanyl-D-alanine from D-alanine, increased gradually with maximum activity observed at the initial stage of sporulation. These results raise the hypothesis that M. xanthus produces and releases D-alanyl-D-alanine during development, and the released D-alanyl-D-alanine may function as an inducer of sporulation.