Two Novel Regulatory Mechanisms in the Synthesis of E. faecalis Virulence Factor Gelatinase (GelE)
Enterococcus faecalis, a Gram-positive bacterium, has been characterized as a commensal organism in the gastrointestinal (GI) tract of humans capable of migrating and transitioning into a pathogenic state. Pathogenic strains of E. faecalis are a leading cause of nosocomial infections in the United States, treatment of which is complicated by the formation of biofilms which protect the bacteria from antimicrobial agents. A transposon (Tn) mutant library was created to identify genetic determinants of biofilm formation. One gene, encoding Biofilm phosphatase (bph), is required for surface attachment and biofilm formation in wild-type (OG1RF) strains. Transposon mutant strains lacking bph display significant growth and attachment defects, in addition to global changes in gene expression genes. Another gene, prsA, which encodes a foldase, was also found to exhibit biofilm defects in arrangement and architecture. Deletion or knockdown of bph (Δbph) or prsA (prsA-Tn) results in markedly reduced or complete lack of production of gelatinase (GelE), respectively. GelE, a secreted Zn-metalloprotease, is implicated in a “housekeeping role,” on the surface of E. faecalis. The precise gelE transcription rates and gelatinase activity in both mutants is unknown. Determining the regulatory role of PrsA and Bph in GelE synthesis is critical for a complete understanding of E. faecalis biology. Here, I show that Bph plays a role in transcriptional regulation of gelatinase synthesis, while PrsA is involved in post-transcriptional processing of GelE. Decreased GelE activity in Δbph is due to decreased gelatinase expression which is mediated by the Fsr-quorum sensing system. The lack of gelatinase activity in prsA mutants cannot be explained by decreased gelE expression, suggesting the defect arises later during synthesis. These results establish two novel regulatory mechanisms in the synthesis of the gelatinase and advance our understanding of E. faecalis virulence processes. These findings will serve as a foundation for future investigations into E. faecalis cell biology while also offering potential targets for infection treatment.