| Description |
The resistance exhibited by C. albicans biofilm, a common medical complication, has become a clinically important problem. Our lab was the first to separate and identify a small subpopulation of biofilm persister/ basal blastospores that are highly resistant to amphotericin B (AmB). An important aspect of the persister cells is that they are tightly adhered to the surface; the larger portion of the biofilm is easily sloughed off. While the mechanisms involved in formation of persister cell subpopulation are poorly understood, resistance could be due a number of factors. This study focuses on three possible mechanisms: 1) A reduction of ergosterol in the plasma membrane, 2) Increased production or cross linking of β-glucans in the cell wall and 3) Adhesion to surfaces. Ergosterol is the primary sterol in C. albicans. AmB acts by binding to ergosterol and creating channels in the membrane, which then causes unregulated leakage of ions, damages the cell and eventually causes its death. Ergosterol and intermediates were measured in the persister cells and compared to other biofilm fraction and planktonic. Results show a decrease in ergosterol and formation of intermediates and side products only in persister cells. Though the ergosterol reduction in persister cells is consistent with their resistant behavior; it still does not explain the magnitude of resistance exhibited by these persister cells. The cell wall is physically and physiologically different from the plasma membrane. Direct analysis of the cell wall is scientifically challenging; however, one can analyze signaling pathways involved in cell wall synthesis. One such pathway involves the phosphorylation of MAP-kinase (MAPK). Results show that Mkc1 and Cek1 MAPK were activated in only the persister cells. The most striking feature of the persister cell population was their increased adherence to the tubing. Farnesol is a known quorum sensing agent for C. albicans. Results show that farnesol had drastically reduced the attachment of cells to the tubing surface. This is an important finding, as it gives us a new avenue to impede the process of persister cell formation. In summary,this work helped in gaining further insight into the formation of the persister cells. |
