C albicans and Stress

The ability of the C. albicans to resist various stresses is of great importance in its ability to infect and cause disease (Kraus & Heitman, 2003; Kruppa & Calderone, 2006; Monge et al., 2006). Stresses influencing C. albicans behaviour during infection and disease include oxidative and nitrosative stresses and nutrient limitation.

Transcript profiling experiments have shown that C. albicans has both a core stress response and stress-specific responses (Enjalbert et al., 2006). The Hog1p pathway was found to be involved in responses to osmotic and heavy metal stresses, but not to oxidative stress (Enjalbert et al., 2006). However, the transcription factor Cap1p has been demonstrated to be involved in the oxidative stress response via multiple pathways, including the cellular antioxidant defence system (Enjalbert et al., 2006; Wang et al., 2006). Transcript profiling experiments demonstrated that 76 out of 89 genes differentially expressed in response to oxidative stress were Cap1p-dependent (Wang et al., 2006). Cap1p has also been shown to regulate expression of genes related to intracellular redox in response to oxidative stress (Wang et al., 2007).

Homologues of S. cerevisiae stress response zinc-finger transcription factor genes, MSN4 and MNL1, have been shown to have little or no effect upon resistance of C. albicans to heat, osmotic, ethanol, nutrient, oxidative, or heavy metal stresses (Nicholls et al., 2004), suggesting divergence of stress responses in these fungi.

The response of C. albicans to nitric oxide and nitrosative stress has also been examined (Hromatka et al., 2005). Many genes were transiently altered in their expression levels, but a subset of nine genes remained at elevated levels during exposure to nitric oxide. These genes include YHB1 (encoding a flavohaemoglobin, proteins involved in detoxifying nitric oxide in a variety of pathogens), AOX1 and AOX 2 (encoding proteins suggested to function to reduce nitric oxide-induced oxidative stress), SSU1, CTR2, and RBT5. Deletion of the YHB1 gene resulted in several changes in transcription pattern, including the inappropriate expression of hypha-associated genes under non-inducing conditions (Hromatka et al., 2005). This C. albicans strain was also attenuated in virulence, which may be due either to the nitric oxide or the filamentous phenotypes.

Proteomic studies of nutrient limitation in C. albicans have included responses to amino acid starvation (Yin et al., 2004) and reduced Ura3p (Brand et al., 2004). Amino acid starvation was found to induce not only amino acid biosyn-thetic proteins, but proteins involved in carbon metabolism (Yin et al., 2004).

Proteins affected by Ura3p deficiency included those involved in purine and pyrimidine biosynthesis, heme biosynthesis, and aromatic amino acid turnover (Brand et al., 2004).

Cure Your Yeast Infection For Good

Cure Your Yeast Infection For Good

The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.

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