GENES REQUIRED FOR BOTH GLIDING MOTILITY AND DEVELOPMENT IN MYXOCOCCUS-XANTHUS

Myxococcus xanthus cells can glide both as individual cells, dependent on Adventurous motility (A motility), and as groups of cells, depende nt upon Social motility (S motility). Tn5-lac mutagenesis was used to generate 16 new A(-) and nine new S- mutations. In contrast with previ ous results, we find that subsets of A(-) mutants are defective in fru iting body morphogenesis and/or myxospore differentiation. All S- muta nts are defective in fruiting body morphogenesis, consistent with prev ious results. Whereas some S- mutants produce a wild-type complement o f spores, others are defective in the differentiation of myxospores. T herefore, a subset of the A genes and all of the S genes ate critical for fruiting body morphogenesis. Subsets of both A and S genes are ess ential for sporulation. Three S::Tn5-lac insertions result in surprisi ng phenotypes. Colonies of two S- mutants glide on 'swim' (0.35% agar) plates to form fractal patterns. These S- mutants are the first examp les of a bacterium in which mutations result in fractal patterns of co lonial spreading. An otherwise wild-type strain with one S- insertion resembles the frz(-) sglA1(-) mutants upon development, suggesting tha t this S- gene defines a new chemotaxis component in M. xanthus.