Staphyloxanthin mutants of Staphylococcus aureus and their response to antimicrobials
Miears, William Hunter
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Staphyloxanthin is a golden pigment that is produced by the bacterium, Staphylococcus aureus. This pigment is a virulence factor for the bacterium and is hypothesized to have the dual function of acting as an antioxidant to protect against action of oxidizing agents, a common form of immune response in the human body, and stabilizing the cell membrane, much like cholesterol does in human cells. In this experiment, mutants with little or no staphyloxanthin were successfully created using UV light. These mutants were then tested against various agents, including oxidants, cell membrane active antibiotics, and Pseudomonas aeruginosa exoproducts, to determine if there was a difference in bacterial response between the mutants and the wild type, or non-mutated, bacterium that still produced the staphyloxanthin pigment. I hypothesized that the lack of staphyloxanthin would cause the mutant bacteria to be more drastically affected by the antibacterial agents. This was tested using a standard Kirby-Bauer method where the test compounds are impregnated into standard filter paper discs and tested against lawns of bacteria. Zones of inhibition were measured after 48 hours. Among other data recorded was the influence on pigment production of the various test compounds. Results indicate that differentially pigmented mutants of S. aureus differ in their response to cell membrane active antibiotics and P. aeruginosa exoproducts.