Regulation of Aromatic Alcohol Production in Candida albicans

Abstract

Colonization by the fungal pathogen Candida albicans varies significantly, depending upon the pH and availability of oxygen. Because of our interest in extracellular molecules as potential quorum-sensing molecules, we examined the physiological conditions which regulate the production of the aromatic alcohols, i.e., phenethyl alcohol, tyrosol, and tryptophol. The production of these fusel oils has been well studied for Saccharomyces cerevisiae. Our data show that aromatic alcohol yields for C. albicans are determined by growth conditions. These conditions include the availability of aromatic amino acids, the pH, oxygen levels, and the presence of ammonium salts. For example, for wild-type C. albicans, tyrosol production varied 16-fold merely with the inclusion of tyrosine or ammonium salts in the growth medium. Aromatic alcohol production also depends on the transcription regulator Aro80p. Our results are consistent with aromatic alcohol productionaromatic transaminases (gene products for ARO8 and ARO9), aromatic decarboxylase (ARO10), and alcohol dehydrogenase (ADH)-via the fusel oil pathway. The expression of ARO8, ARO9, and ARO10 is also pH dependent. ARO8 and ARO9 were alkaline upregulated, while ARO10 was alkaline downregulated. The alkalinedependent change in expression of ARO8 was Rim101 independent, while the expression of ARO9 was Rim101 dependent.

Assessment of Tryptophol Genotoxicity in Four Cell Lines In Vitro: A Pilot Study with Alkaline Comet Assay

“…The role of tryptophol (3-indole-ethanol) in the quorum sensing of C. albicans was established in 2000's (7). This aromatic alcohol ( Figure 1) is formed as the end product of tryptophan catabolism in certain as tryptophol producer (7,14) -may be localised but can also become a systemic disease, various organs, tissues, and cell types in the host invaded by C. albicans are potential targets of tryptophol toxicity.…”

“…This aromatic alcohol ( Figure 1) is formed as the end product of tryptophan catabolism in certain as tryptophol producer (7,14) -may be localised but can also become a systemic disease, various organs, tissues, and cell types in the host invaded by C. albicans are potential targets of tryptophol toxicity. It is also reasonable to anticipate that different cells would express different DNA sensitivity to tryptophol, but we have not got this information as yet.…”

“…Oval yeast cells are more prevalent in commensal interactions, while in opportunistic infections fi lamentous forms prevail. Such infections range from localised mycoses (superfi cial and deep-seated ones) to serious systemic diseases that may lead to death (mainly in immunocompromised hosts) (5,7).…”

“…The morphological transition of C. albicans is infl uenced by numerous stimuli such as increased pH and temperature, low availability of nutrients, low cell density, and the presence of certain compounds that promote or block filamentation (7)(8)(9). Aromatic alcohol tyrosol, for instance, stimulates morphological transition of C. albicans from yeasts to hyphae (3), while farnesol, farnesoic acid, tryptophol, and 2-phenylethanol mostly repress hyphal development (2,4,(9)(10)(11).…”

Quorum sensing activity and control of yeast-mycelium dimorphism in Ophiostoma floccosum

“…For instance, in both S. cerevisiae (Chen and Fink 2006) and Can. albicans (Ghosh et al 2008) ammonium salts restrict the production of fusel alcohols (signaling compounds for these fungal species) due to the inhibition of their biosynthetic pathway, whereas poor N sources such as l-proline, γ-amino butyric acid (GABA), urea, purines, and polyamines activate it.…”