Enterococcus faecalis is a Gram-positive bacterium that lives as a commensal organism in the mammalian gastrointestinal tract or as an opportunistic pathogen. Our lab discovered that mutation of the eutK gene attenuates virulence of E. faecalis in the C. elegans model host. eutK is part of the ethanolamine metabolic pathway which was previously unknown in E. faecalis. I discovered the presence two unique posttranscriptional regulatory features that control expression of eut locus genes. The first feature I found is an AdoCBL riboswitch, a cis acting RNA regulatory element that acts as a positive regulator of gene expression. The second feature I discovered is a unique two-component system, EutVW. The EutV response regulator contains an ANTAR family domain, which bind RNA and act as transcriptional antitermination factors. I determined that induction of expression of several genes in the eut locus is dependent on ethanolamine, AdoCBL and the two-component system. AdoCBL and ethanolamine regulate eut locus genes in a synergistic manor, as both compounds are required for induction of gene expression. Additionally, I discovered eutG is regulated by a unique mechanism of antitermination. Both AdoCBL riboswitch and the EutV control the stability of a downstream terminator. EutV potentially acts through a novel antitermination mechanism in which a dimer of EutV binds to a pair of mRNA stem loops forming an antitermination complex. My data show a unique mechanism by which two environmental signals are integrated to by two different posttranscriptional regulators to regulate a single locus.
Multiple posttranscriptional regulatory features control expression of ethanolamine utilization genes in Enterococcus faecalis