Disruption of aldA influences the developmental process in Myxococcus xanthus

Previously, we identified a gene (aldA) from Myxococcus xanthus, which we s uggested encoded the enzyme alanine dehydrogenase on the basis of similarit y to known Aid protein sequences (M, J. Ward, H. Lew, A. Treuner-Lange, and D, R, Zusman, J, Bacteriol. 180:5668-5675, 1998), In this study, we have c onfirmed that aldA does encode a functional alanine dehydrogenase, since it catalyzes the reversible conversion of alanine to pyruvate and ammonia. Wh ereas an aldA gene disruption mutation did not significantly influence the rate of growth or spreading on a rich medium, AldA was required for growth on a minimal medium containing L-alanine as the major source of carbon. Und er developmental conditions, the aldA mutation caused delayed aggregation i n both wild-type (DZ2) and FB (DZF1) strains. Poorly formed aggregates and reduced levels of spores were apparent in the DZ2 aldA mutant, even after p rolonged development.