Salmonella enterica serovar Typhimurium STM1266 encodes a regulator of curli biofilm formation: The brfS gene

Abstract

The major biofilm pathway in Salmonella enterica serovar Typhimurium involves specific growth conditions that induce the csgA gene whose product forms surface curli fibers that mediate biofilm formation. We have found that the previously uncharacterized STM1266 gene in S. Typhimurium plays a role in regulating biofilm formation via the curli pathway. S. Typhimurium ΔSTM1266 strains display a biofilm defect, and overexpression of STM1266 results in enhanced biofilm formation. STM1266 deletion resulted in lowered csgA expression using promoter-reporter β-galactosidase assays, and csgA and csgD deletions abrogate the effects of STM1266 overexpression on biofilm formation while deletion of bcsA (encoding an essential enzyme for cellulose formation) has no effect. In a mouse infection model, the ΔSTM1266 strain displayed results similar to those seen for previously reported ΔcsgA strains. The STM1266 gene is predicted to encode a DNA-binding transcriptional regulator of the MerR family and is homologous to the Escherichia coli BluR regulator protein. We respectfully propose to ascribe the name brfS (biofilm regulator for Salmonella Typhimurium) to the STM1266 gene.