The psi operon of Rhizobium leguminosarum biovar phaseoli: identification of two genes whose products are located at the bacterial cell surface

psi operon of Rhizobium leguminosarum biovar phaseoli encodes three open reading frames, PsiA, PsiB and ORF-P. PsiA gene inhibits exopolysaccharide synthesis, causing R. leguminosarum strains to color with dye calcofluor. phoA defective gene insertions at PsiA and PsiB are identified and sequenced. PsiA-phoA and PsiB-phoA protein fusions and alkaline phosphatase activity reveal PsiA and PsiB located in the inner bacterial membrane.