Role of epaq, a previously uncharacterized enterococcus faecalis gene, in biofilm development and antimicrobial resistance

Michelle L. Korir, Jennifer L. Dale, Gary M. Dunny

Research output: Contribution to journalArticlepeer-review

4 Scopus citations

Abstract

Enterococcus faecalis is a commensal of the human gastrointestinal tract; it is also an opportunistic pathogen and one of the leading causes of hospitalacquired infections. E. faecalis produces biofilms that are highly resistant to antibiotics, and it has been previously reported that certain genes of the epa operon contribute to biofilm-associated antibiotic resistance. Despite several studies examining the epa operon, many gene products of this operon remain annotated as hypothetical proteins. Here, we further explore the epa operon; we identified epaQ, currently annotated as encoding a hypothetical membrane protein, as being important for biofilm formation in the presence of the antibiotic daptomycin. Mutants with disruptions of epaQ were more susceptible to daptomycin relative to the wild type, suggesting its importance in biofilm-associated antibiotic resistance. Furthermore, the ΔepaQ mutant exhibited an altered biofilm architectural arrangement and formed small aggregates in liquid cultures. Our cumulative data show that epa mutations result in altered polysaccharide content, increased cell surface hydrophobicity, and decreased membrane potential. Surprisingly, several epa mutations significantly increased resistance to the antibiotic ceftriaxone, indicating that the way in which the epa operon impacts antibiotic resistance is antibiotic dependent. These results further define the key role of epa in antibiotic resistance in biofilms and in biofilm architecture.

Original languageEnglish (US)
Article numbere00078-19
JournalJournal of bacteriology
Volume201
Issue number18
DOIs
StatePublished - Sep 1 2019

Bibliographical note

Funding Information:
This work was supported by the National Institutes of Health (grant AI122742) as well as the NIH’s National Center for Advancing Translational Sciences (grants TL1R002493 and UL1TR002494). Parts of this work were carried out in the Characterization Facility at the University of Minnesota, which receives partial support from the National Science Foundation (NSF) through the MRSEC program. Polysaccharide composition analysis was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, U.S. Department of Energy grant (DESC0015662) at the Center for Plant and Microbial Complex Carbohydrates in the Complex Carbohydrate Research Center (CCRC) at the University of Georgia.

Funding Information:
We thank Julia Willett for providing the attachment assay and eDNA quantification protocols and Aaron Barnes for guidance with microscopy. This work was supported by the National Institutes of Health (grant AI122742) as well as the NIH's National Center for Advancing Translational Sciences (grants TL1R002493 and UL1TR002494). Parts of this work were carried out in the Characterization Facility at the University of Minnesota, which receives partial support from the National Science Foundation (NSF) through the MRSEC program. Polysaccharide composition analysis was supported by the Chemical Sciences, Geosciences and Biosciences Division, Office of Basic Energy Sciences, U.S. Department of Energy grant (DESC0015662) at the Center for Plant and Microbial Complex Carbohydrates in the Complex Carbohydrate Research Center (CCRC) at the University of Georgia. The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the NIH, NSF, or CCRC.

Publisher Copyright:
© 2019 American Society for Microbiology.

Keywords

  • Cell wall polysaccharide
  • Cell wall stress
  • Functional genomics
  • Intrinsic resistance to antibiotics

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