Wild Saccharomyces cerevisiae strains display biofilm-like morphology in contact with polyphenols from grapes and wine

Polyphenols are a major component of wine grapes, and contribute to color and flavor, but their influence upon yeast growth forms has not been investigated. In this work we have studied the effect of polyphenols on the ability of natural isolates of wine-related Saccharomyces cerevisiae strains to form biofilms attaching to plastic surfaces, to grow as mat colonies, to invade media, and to display filamentous growth. The use of carbon- and nitrogen-rich or deficient media simulated grape juice fermentation conditions. The addition of wine polyphenols to these media affected biofilm formation, and cells exhibited a wide variety of invasiveness and mat formation ability with associated different growth and footprint patterns. Microscopic observation revealed that some strains switched to filamentous phenotypes which were able to invade media. The wide range of phenotypic expression observed could have a role in selection of strains suitable for inoculated wine fermentations and may explain the persistence of yeast strains in vineyard and winery environments.