Enterococcus faecalis is a major cause of hospital-acquired infections and also plays a key role in the dissemination of antibiotic resistance and virulence genes to other bacterial pathogens. This application seeks continued support for basic studies of a unique peptide-based signaling system that allows cells carrying an antibiotic resistance/virulence plasmid called pCF10 to regulate expression of genes involved in resistance transfer and virulence. The key players in the signaling system include the cCF10 peptide pheromone (signal molecule) and the iCF10 peptide pheromone inhibitor which antagonizes cCF10. The receptor for these peptides is a transcription factor called PrgX, which regulates expression of the pCF10 prgQ operon encoding the virulence and plasmid transfer genes. The pheromone response machinery comprises a sensitive and robust biological switch, where multiple regulatory circuits act in concert to amplify the direct response to pheromone, and to enable the host cell to sense different kinds of environmental cues. Post-transcriptional regulatory mechanisms involving novel small RNAs also play a major role in the pheromone response. The proposed studies are focused on elucidating the quantitative effects mechanistic aspects of various regulatory circuits, and on determining the mechanisms by which the pheromone-induced state can be returned to basal levels of expression following transfer of the plasmid to a new host. This work will reveal insights into regulation of microbial virulence by cell-cell signaling, applicable to many organisms, and may also facilitate new strategies for development of antimicrobial agents.

Public Health Relevance

This research investigates the process by which bacteria communicate with one another using small molecule signals. In this case the signal causes cells carrying antibiotic resistance genes to transfer copies of these genes to other cells. The bacterial species involved is Enterococcus faecalis and the transfer process increases the virulence and antibiotic resistance of strains that cause infections in hospitals. The basic knowledge gained from this research may provide new insights into the development of more effective forms of antimicrobial chemotherapy.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Special Emphasis Panel (ZRG1-GGG-F (02))
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Sledjeski, Darren D
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University of Minnesota Twin Cities
Schools of Medicine
United States
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Bhatty, Minny; Cruz, Melissa R; Frank, Kristi L et al. (2015) Enterococcus faecalis?pCF10-encoded surface proteins PrgA, PrgB (aggregation substance) and PrgC contribute to plasmid transfer, biofilm formation and virulence. Mol Microbiol 95:660-77
Johnson, Christopher M; Chen, Yuqing; Lee, Heejin et al. (2014) Identification of a conserved branched RNA structure that functions as a factor-independent terminator. Proc Natl Acad Sci U S A 111:3573-8
Cook, Laura C C; Dunny, Gary M (2014) The influence of biofilms in the biology of plasmids. Microbiol Spectr 2:0012
Chatterjee, Anushree; Cook, Laura C C; Shu, Che-Chi et al. (2013) Antagonistic self-sensing and mate-sensing signaling controls antibiotic-resistance transfer. Proc Natl Acad Sci U S A 110:7086-90
Caserta, Enrico; Haemig, Heather A H; Manias, Dawn A et al. (2012) In vivo and in vitro analyses of regulation of the pheromone-responsive prgQ promoter by the PrgX pheromone receptor protein. J Bacteriol 194:3386-94
Johnson, Christopher M; Haemig, Heather H A; Chatterjee, Anushree et al. (2011) RNA-mediated reciprocal regulation between two bacterial operons is RNase III dependent. MBio 2:
Cook, Laura; Chatterjee, Anushree; Barnes, Aaron et al. (2011) Biofilm growth alters regulation of conjugation by a bacterial pheromone. Mol Microbiol 81:1499-510
Dunny, Gary M; Johnson, Christopher M (2011) Regulatory circuits controlling enterococcal conjugation: lessons for functional genomics. Curr Opin Microbiol 14:174-80
Chatterjee, Anushree; Johnson, Christopher M; Shu, Che-Chi et al. (2011) Convergent transcription confers a bistable switch in Enterococcus faecalis conjugation. Proc Natl Acad Sci U S A 108:9721-6
Johnson, Christopher M; Manias, Dawn A; Haemig, Heather A H et al. (2010) Direct evidence for control of the pheromone-inducible prgQ operon of Enterococcus faecalis plasmid pCF10 by a countertranscript-driven attenuation mechanism. J Bacteriol 192:1634-42

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