Editors' ChoiceMicrobiology

Environmental Sensing

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Science's STKE  10 May 2005:
Vol. 2005, Issue 283, pp. tw182
DOI: 10.1126/stke.2832005tw182

Candida species are important human pathogens that bind to host epithelial cells through specific adhesive molecules, encoded by the yeast EPA genes. Most of the EPA genes are encoded in subtelomeric regions and suppressed by Sir3-mediated chromatin silencing, a mechanism that relies on the availability of the coenzyme nicotinamide adenine dinucleotide (NAD+). Domergue et al. discovered that EPA6 silencing was specifically lifted in urinary tract infections but not in bloodstream infections. Strikingly, unlike other yeasts, Candida glabrata cannot manufacture NAD+ from tryptophan, and the pathogen is reliant on the host to supply the precursor, nicotinic acid. The pathogen exploits this limitation to sense its environment: In the urinary tract, little nicotinic acid is available, so the adhesion gene suppression is lifted and the cells can specifically attach to uroepithelial cells.

R. Domergue, I. Castaño, A. De Las Peñas, M. Zupancic, V. Lockatell, J. R. Hebel, D. Johnson, B. P. Cormack, Nicotinic acid limitation regulates silencing of Candida adhesins during UTI. Science 308, 866-870 (2005). [Abstract] [Full Text]