Fig. 2.

Ssr2 is necessary for inversion of all seven polysaccharide promoter regions. (A) Diagrammatic representation of the PCR method used to detect DNA inversions of each of the seven invertible promoter regions. Each of the primers contained within the IRs was used in a PCR with both the upstream and downstream primers individually. (B) EtBr-stained agarose gel demonstrating that the promoters of each of the seven polysaccharide biosynthesis loci is present in only a single orientation in the Δssr2 mutants relative to wild type. Three distinct locked polysaccharide promoter patterns were detected in the panel of eight mutants exemplified by Δssr2 mutants 2, 8, and 44. The bottom panel shows complementation of the locked genotypes when ssr2 is added in trans to Δssr2 mutant 44 (pKGW4R). (C) Western blots demonstrating the polysaccharide phenotypes of the three representative Δssr2 mutants.