Proteomic analysis of the pH response in the fungal pathogen Candida glabrata

Micro-organisms must adapt to environmental change to survive, and this is particularly true for fungal pathogens such as Candida glabrata. C. glabrata is found both in the environment and in diverse niches in its human host. The ambient pH of these niches varies considerably, and therefore we have examined the response of C. glabrata to changes in ambient pH. using a proteomic approach. Proteins expressed in C. glabrata cells growing at pH 4.0, 7.4 or 8.0 were compared by 2-DE, and 174 spots displaying reproducible and statistically significant changes in expression level were identified by peptide mass fingerprinting, thereby extending our 2-DE map of the C. glabrata proteome to a total of 272 identified spots. Proteins involved in glucose metabolism, the TCA cycle, respiration and protein synthesis were expressed at lower levels during growth at pH 7.4 and/or 8.0, whereas proteins involved in stress responses and protein catabolism were expressed at higher levels under these alkaline conditions. Our data suggest that C. glabrata perceives low pH as less stressful than higher pH. This contrasts with another opportunistic fungal pathogen of humans, Candida albicans.