Candida albicans is an opportunistic fungal species that colonizes the gastrointestinal, oral, and genital surfaces and the skin of most healthy people. Unfortunately, C. albicans also causes a range of diseases, especially in immunocompromised individuals, and its transition to pathogenesis is associated with specific cellular states. The yeast can form hyphae, which allow them to penetrate host cells, release toxins that damage host epithelial cells, and form pathogenic biofilms. Approximately 75% of women contract vulvovaginal candidiasis over the course of their lives. Candida species are also the fourth leading cause of nosocomial bloodstream infections. C. albicans comprises most of these infections in both cases. C. albicans research tends to focus on the formation of biofilms, so this project studies another key cell type of the biofilm cycle: dispersed cells, which have a higher resistance to chemical and physical stressors than planktonic cells. The two stressors used were hydrogen peroxide and anthocyanins. H2O2 causes oxidative stress, which is used by immune cells to target pathogens. Anthocyanins are a family of pigmented phytochemicals that have antioxidant properties, which could negate the effect of the H2O2 on C. albicans. The goal of this project was to quantify the resistance of planktonic and dispersed C. albicans to H2O2 and anthocyanins—individually and in combination—to determine whether anthocyanins enhance or inhibit C. albicans growth in the presence of H2O2 and to understand the dynamics of this crucial but understudied cellular state. To test the effect of stressors on different cell types, planktonic and dispersed cells were cultured in YPD and incubated with varying concentrations of H2O2 or anthocyanins for 1 hour before being drop-plated onto YPD agar. Results showed that dispersed cells were orders of magnitude more resistant to H2O2 than planktonic cells. The anthocyanins did not affect either planktonic or dispersed cell counts. Even though the highest tested dose of anthocyanins did not affect the viability of either planktonic or dispersed cells, it exhibited a synergistic effect on both when combined with H2O2, noticeably reducing the growth of dispersed cells. The synergistic effect of the anthocyanins suggests that the increased resistance to oxidative stress of dispersed cells may be due to changes in cell wall or membrane architecture, a hypothesis that will be tested via cell permeability assays and other methods of disruption. Different strains of C. albicans will also be used to verify the generalizability of our findings. This research is useful for determining if anthocyanin-based drug therapies would be beneficial for treating C. albicans infections and learning more about how stressors affect dispersed and planktonic cells.
