Phenotypic analyses of frz and dif double mutants of Myxococcus xanthus.

Myxococcus xanthus is a Gram-negative gliding bacterium that aggregates and develops into multicellular fruiting bodies in response to starvation. Two chemosensory systems (frz and dif), both of which are homologous to known chemotaxis proteins, were previously identified through characterization of various developmental mutants. This study aims to examine the interaction between these two systems since both of them are required for fruiting body formation of M. xanthus. Through detailed phenotypic analyses of frz and dif double mutants, we found that both frz and dif are involved in cellular reversal and social motility; however, the frz genes are epistatic in controlling cellular reversal, whereas the dif genes are epistatic in controlling social motility. The study suggests that the integration of these two chemotaxis systems may play a central role in controlling the complicated social behaviors of M. xanthus.