Reciprocal Regulation between Fur and Two RyhB Homologs in Yersinia pestis, and Roles of RyhBs in Biofilm Formation.

OBJECTIVE: To investigate reciprocal regulation between Fur and two RyhB homologs in Yersinia pestis( Y. pestis), as well as the roles of RyhBs in biofilm formation. METHODS: Regulatory relationships were assessed by a combination of colony morphology assay, primer extension, electrophoretic mobility shift assay and DNase I footprinting. RESULTS: Fur bound to the promoter-proximal DNA regions of ryhB1 and ryhB2 to repress their transcription, while both RyhB1 and RyhB2 repressed the expression of Fur at the post-transcriptional level. In addition, both RyhB1 and RyhB2 positively regulated Y. pestis biofilm exopolysaccharide (EPS) production and the expression of hmsHFRS and hmsT. CONCLUSION: Fur and the two RyhB homologs exert negative reciprocal regulation, and RyhB homologs have a positive regulatory effect on biofilm formation in Y. pestis.