The transcriptional stress response of Candida albicans to weak organic acids.
Bottom Line: Genes commonly up-regulated by WOAs were enriched in several iron transporters, which was associated with an overall decrease in intracellular iron concentrations.Moreover, chronic exposure to any WOA lead to down-regulation of RNA synthesis and ribosome biogenesis genes, which resulted in significant reduction of total RNA levels and of ribosomal RNA in particular.In conclusion, this study suggests that gastrointestinal microbiota might directly influence C. albicans physiology via production of WOAs, with possible implications of how this fungus interacts with its host in both health and disease.
Affiliation: Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore 138648, Singapore.Show MeSH
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Mentions: To shed light on the overall cellular response of C. albicans to WOAs, we used a genome-wide transcriptional profiling approach based on cDNA deep sequencing. Because C. albicans is expected to encounter these bacterial-derived metabolites in the GI tract over prolonged periods of time, we performed the analysis not only on acute but also on several time points of chronic exposure of each individual acid for up to ~3 d (Figure 1A). Four independent C. albicans cultures were grown under each of the following six conditions (for a total of 24 independent cultures): MRS at pH 6.1 (unmodified medium), MRS at pH 5.5 (medium acidified by addition of HCl), or MRS supplemented with 622 mM lactic, 75 mM acetic, 52 mM propionic, or 18 mM butyric acid, all adjusted to pH 5.5 by the addition of NaOH. These WOA concentrations were empirically chosen for their ability to significantly affect the OD of the cultures at both early (4 hr) and late (24 hr) time points compared with untreated or HCl-treated cultures (Figure 1B). To ensure that each culture was analyzed in the early exponential phase of growth, we used a daily serial passaging design, in which samples were harvested on each day at the same time (i.e., 4 hr) after we relaunched the previous overnight culture into fresh medium. Four time points (termed T1−T4), corresponding to each of four subsequent serial passages, were chosen for transcriptome analysis.
Affiliation: Singapore Immunology Network (SIgN), Agency for Science, Technology and Research (A*STAR), Singapore 138648, Singapore.