INDUCTION OF MYXOSPORES IN STIGMATELLA-AURANTIACA (MYXOBACTERIA) - INDUCERS AND INHIBITORS OF MYXOSPORE FORMATION, AND MUTANTS WITH A CHANGED SPORULATION BEHAVIOR

In a screening programme, many new compounds were found that induced myxospore formation in Stigmatella aurantiaca strain Sg al. The most efficient compounds were indole and indole derivatives, e.g. 3-methylindole. With an inducing concentration of 0.07 mm, this compound was about 2000 times more efficient than glycerol. Indole compounds, which have also been found as natural metabolites of myxobacteria, are thus candidates for auto-inducers within the fruiting bodies. Mutants were isolated that were resistant to particular inducers. They often showed cross-resistance to many other inducers. By the sporulation response of three different mutants, the inducers could be classified into four groups. Strains resistant to inducers of, e.g. group I were still sensitive to inducers of groups II and III, and vice versa. This classification was supported by newly discovered inhibitors of induced sporulation. These inhibitors, oxindole and pyrrole, were specific for inducers of group I. The grouping is further supported by differences in the kinetics of myxospore formation. We postulate that S. aurantiaca has three inducer-specific, independent receptors.