| Staphylococcus epidermidis is the most notable member of the Coagulase Negative Staphylococci. The greatest pathogenic attribute of this organism is its ability to produce a biofilm. The enzymes responsible for the synthesis of polysaccharide intercellular adhesin (PIA) are encoded by the four-gene icaADBC operon. This operon has complex regulation, with a many regulatory proteins and environmental factors contributing. This dissertation characterizes two regulators of the icaADBC operon, one that is novel (SarR) and one that (IcaR) has a surprising biofilm phenotype. Divergently transcribed from icaADBC is a negative regulator, icaR. We characterized the unique biofilm phenotype of an icaR mutant. The loss of this icaR disrupts the temporal synthesis of PIA and impairs biofilm maturation. SarR is part of a large family of DNA binding proteins. The function of SarR in S. epidermidis biofilm production has never been studied. We hypothesized that this protein would contribute to abrogation of biofilm synthesis in a manner similar to its SarA paralog. While we determined this protein was a regulator of icaADBC transcript and ultimate biofilm synthesis, we were surprised to learn the SarR regulon is almost entirely different from SarA.;PIA is the major matrix molecule of a S. epidermidis biofilm, however, its synthesis is not essential for biofilm formation or infection. PIA allows biofilms to have tower-like structures and growth in high-sheer environments. PIA also increases static biofilm production and allows for pellicles formation to occur. We hypothesized PIA dependent structures would generate environmental niches where differential gene expression could occur. We used microarrays to test this hypothesis characterizing differences in PIA-negative and PIA-positive biofilms. Additionally, questions about the biofilm maturation process were addressed. These experiments led us to study the metabolism of a maturing biofilm in regards to amino acid utilization, specifically the arginine deiminase operon and its role in microaerobic/anaerobic growth process of biofilm maturation. As a translational aspect of this research we utilized a guinea pig tissue cage model of infection to determine the role of PIA on the efficacy of different antibiotics in treating these infections. |
