EFFECT OF DSP MUTATIONS ON THE CELL-TO-CELL TRANSMISSION OF CSGA IN MYXOCOCCUS-XANTHUS

The dsp locus contains genes involved in the subunit synthesis and/or assembly of fibrils that radiate outward from the Myxococcus xanthus c ell surface and attach to other cells. The csgA gene encodes an extrac ellular protein morphogen which is essential for fruiting body develop ment. The question of whether fibrils are involved in the transmission of CsgA to adjacent cells was investigated in three ways. First, the dsp and csgA mutants were mixed in a ratio of 1:1 and allowed to devel op; fruiting bodies containing spores derived from the csgA mutant wer e formed, suggesting efficient CsgA transfer. Second, the csgA mutatio n affected expression of many developmentally regulated genes differen tly from the way dsp affected their expression. Third, the expression of one developmentally regulated gene, which was partially expressed i n csgA and dsp backgrounds, was almost completely inhibited in the pre sence of both mutations, suggesting that its promoter is regulated ind ependently by two distinct stimuli, one that is csgA dependent and one that is dsp dependent. Together these results argue that fibrils are not necessary for cell-to-cell transmission or perception of CsgA, and their precise function remains unknown.