The quorum-sensing molecule E,E-farnesol--its variable secretion and its impact on the growth and metabolism of Candida species.

Diseases caused by Candida species are an increasing problem. Candida species are associated with high overall mortality, due to a variety of virulence factors such as the yeast-to-hyphal switch and proteolytic enzymes. The phenomenon of microbial communication known as quorum sensing also seems to play an important role. The main characteristics of the quorum-sensing molecule E,E-farnesol are well known for C. albicans. The present study focused on two questions. One of them concerned the secretion of E,E-farnesol by C. albicans and involved a close examination of the effect of the medium (serum) and the origin of the isolates used. The second one dealt with the activity of E,E-farnesol in non-C. albicans species, such as C. tropicalis and C. parapsilosis, e.g. its impact on biofilm formation and growth. Under serum conditions, C. albicans produced up to 58% more E,E-farnesol at 37 degrees C than at 30 degrees C. The growth of all isolates was reduced and delayed by the administration of E,E-farnesol. Of all Candida species, C. tropicalis isolates were most strongly affected by the addition of E,E-farnesol. Biofilm formation on polystyrene was affected by E,E-farnesol treatment in all non-C. albicans species and C. albicans. E,E-farnesol exerts its main effect by altering the metabolic activity and growth inhibition of treated Candida species. The results obtained indicate that the presence of E,E-farnesol in the environment not only regulates the morphology of the Candida species but also affects its fitness. In this regard, the secretion of E,E-farnesol might provide an advantage for members of the microbial community. Copyright 2010 John Wiley & Sons, Ltd.