A DNAK HOMOLOG IN MYXOCOCCUS-XANTHUS IS INVOLVED IN SOCIAL MOTILITY AND FRUITING BODY FORMATION

Myxococcus xanthus is a gram-negative soil bacterium which exhibits a complex life cycle and social behavior. in this study, two development al mutants of M. xanthus were isolated through Tn5 transposon mutagene sis. The mutants were found to be defective in cellular aggregation as well as in sporulation. Further phenotypic characterization indicated that the mutants were defective in social motility but normal in dire cted cell movements. Both mutations were cloned by a transposon-taggin g method. Sequence analysis indicated that both insertions occurred in the same gene, which encodes a homolog of DnaK. Unlike the dnaK genes in other bacteria, this M. xanthus homolog appears not to be regulate d by temperature or heat shock and is constitutively expressed during vegetative growth and under starvation. The defects of the mutants ind icate that this DnaK homolog is important for the social motility and development of M. xanthus.