Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Microbiology and Immunology

Supervisor

Dr. David Heinrichs

2nd Supervisor

Dr. Martin McGavin

Joint Supervisor

Abstract

USA300, a strain of community-associated methicillin resistant Staphylococcus aureus (CA-MRSA), has become prevalent in the community. Colonization of human skin requires mechanisms that allow this bacterium to overcome the innate immune defenses on the skin, including secretion of antimicrobial lipids. Antimicrobial lipids inhibit S. aureus growth and induce the staphylococcal proteolytic cascade, producing aureolysin (Aur) which processes the lipase glycerol ester hydrolase (Geh). Nearly all S. aureus strains secrete Geh, yet little information exists concerning its function. Using purified Aur and Geh we confirm that aureolysin processes proGeh to Geh. We then confirmed that geh was required for lipase activity and both forms of the purified enzyme had lipase activity. Finally we showed that optimal growth in trilinolein requires Aur, and might reflect a requirement for the proGeh form of the enzyme to convert trilinolein into toxic linoleic acid, despite that fact that both unprocessed and processed Geh catalyze the hydrolysis of trilinolein.