Enterococci were once thought to be harmless, commensal organisms that colonize the gastrointestinal tract of humans and other mammals. In the last 30 years, however, concern has grown in the clinical setting over two particular species, Enterococcus faecalis and Enterococcus faecium, which are frequently found to be the etiologic agents of nosocomial infections. Aminoacyl-phosphatidylglycerol synthases (aaPGSs) are integral membrane proteins that add amino acids to phosphatidylglycerol (PG) in the cellular envelope of bacteria. Addition of amino acids to PG confers resistance to various therapeutic antimicrobial agents, and contributes to evasion of the host immune response in a number of clinically relevant microorganisms. E. faecium possesses two distinct aaPGSs: aaPGS1 and aaPGS2. In addition, another gene coding for a putative hydrolase (pHyd) is located in the same operon as aaPGS2, and has no known function. To investigate the physiological relevance of aa-PG formation, and the function of aaPGS1, aaPGS2, and pHyd in E. faecium, we generated individual knockouts of these genes using a markerless deletion strategy. Deletion of aaPGS1 did not noticeably alter lipid aminoacylation, whereas deletion of aaPGS2 led to a loss of aa-PG synthesis. Deletion of pHyd also led to a loss of lipid aminoacylation; however, additional experiments are needed to verify that expression of aaPGS2 (which resides just downstream in the same operon) is unaffected in the pHyd-deletion strain. Development of the mutant strains described here will enable us to investigate additional phenotypes associated with these genes, and to determine whether aa-PG formation contributes to antibiotic resistance in E. faecium as in several other pathogenic microorganisms.
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Bachelor of Science (B.S.)
Burnett School of Biomedical Sciences
Molecular Biology and Microbiology
Dissertations, Academic -- Medicine;Medicine -- Dissertations, Academic
Length of Campus-only Access
Honors in the Major Thesis
Harrison, Jesse, "Physiological relevance of a trna-dependent mechanism for membrane modification in enterococcus faecium" (2012). HIM 1990-2015. 1778.