The Transcriptional Response of Candida albicans to Weak Organic Acids, Carbon Source and MIG1 Inactivation Unveils a Role for HGT16 in Mediating the Fungistatic Effect of Acetic Acid

Candida albicans is a resident fungus of the human intestinal microflora. Commonly isolated at low abundance in healthy people, C. albicans outcompetes local microbiota during candidiasis episodes. Under normal conditions, members of the human gastrointestinal microbiota were shown to keep C. albicans colonization under control. By releasing weak organic acids (WOAs), bacteria are able to moderate yeast growth. This mechanism displayed a synergistic effect in vitro with the absence of glucose in medium of culture, which underline the complex interaction that C. albicans faces in its natural environment. Inactivation of the transcriptional regulator MIG1 in C. albicans results in a lack of sensitivity to this synergistic outcome. To decipher C. albicans transcriptional responses to glucose, WOAs and the role of MIG1, we performed RNA sequencing on four biological replicates exposed to combinations of these 3 parameters. We were able to characterise the i) glucose response, ii) response to acetic and butyric acid, iii) MIG1 regulation of C. albicans and iv) genes responsible for WOAs resistance. We identified a group of 6 genes linked to WOAs sensitivity in a glucose-MIG1-dependent manner and inactivated one of these genes, the putative glucose transporter HGT16, in a SC5314 wild-type background. As expected, the mutant displayed a partial complementation to WOAs resistance in absence of glucose. This result points towards a mechanism of WOAs sensitivity in C. albicans involving membrane transporters which could be exploited to control yeast colonisation in human body niches.

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