Trehalose accumulation by tropical yeast strains submitted to stress conditions

Trehalose, a non-reducing disaccharide that accumulates in Saccharomyces cerevisiae, has been implicated in survival under various stress conditions by acting as membrane protectant, as a supplementary compatible solute or as a reserve carbohydrate which may be mobilized during stress. However, most of these studies have been done with strains isolated from European or Asian habitats of temperate climate. In this study, yeasts living in tropical environments, isolated from different microhabitats in Southeastern Brazil, were used to evaluate whether trehalose contributes to survival under osmotic, ethanol and heat stress. The survival under severe stress was compared to a well-characterized laboratorial wild-type strain (D273-10B). Most of the Saccharomyces cerevisiae strains isolated from Drosophila in Tropical Rain Forest were able to accumulate trehalose after a preconditioning treatment at 40 degrees C for 1 h. The amount of intracellular trehalose levels was better correlated with survival during a challenging heat shock at 50.5 degrees C for 8 min. Saccharomyces cerevisiae and Candida guilliermondii were observed to be thermotolerant as well as osmotolerant. No clear correlation between intracellular trehalose levels and survival could be derived during ethanol stress. In some cases, the amount of trehalose accumulated before the ethanol stress seemed to play an important role for the survival of these strains.