Characterization ofbcsAMutations That Bypass Two Distinct Signaling Requirements forMyxococcus xanthusDevelopment

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Abstract
The BsgA protease is required for starvation-induced development inMyxococcus xanthus.Bypass suppressors of absgAmutant were isolated to identify genes that may encode additional components of BsgA protease-dependent regulation of development. Strain M951 was isolated following Tn5mutagenesis of absgAmutant and was capable of forming fruiting bodies and viable spores in the absence of the BsgA protease. The Tn5Ω951 insertion was localized to a gene,bcsA, that encodes a protein that has significant amino acid similarity to a group of recently described flavin-containing monooxygenases involved in styrene catabolism. Mutations inbcsAbypassed the developmental requirements for both extracellular B and C signaling but did not bypass the requirement for A signaling. Bypass of the B-signaling requirement by thebcsAmutation was accompanied by restored expression of a subset of developmentally inducedlacZfusions to the BsgA protease-deficient strain.bcsAmutant cells developed considerably faster than wild-type cells at low cell density and altered transcriptional levels of a developmentally induced, cell-density-regulated gene (Ω4427), suggesting that thebcsAgene product may normally act to inhibit development in a cell-density-regulated fashion. Bypass of the requirements for both B and C signaling bybcsAmutations suggests a possible link between these two genetically, biochemically, and temporally distinct signaling requirements.