Phenomic analysis and cell wall remodulation ofSaccharomyces cerevisiaeflor strains in the presence of different nitrogen sources

Flor yeasts ofSaccharomyces cerevisiaeare the main actors in the biological ageing of Sherry wines by developing an air-liquid biofilm, calledvelumat the surface of wine at the end of fermentation. The air-liquid biofilm occurs due to a complex mechanism which is similar to many microbial biofilms. Thevelumphenotype is mainly regulated by the expression of a highly O-glycosylated cell wall proteinFlo11which by turn contributes to the hydrophobicity and electrostatic charge of the cell wall which are crucial for unspecific interactions and adhesion capacity of yeasts. In this study we characterized the interactions of flor yeasts with a series of nitrogen compounds known for their hydrophobicity and/or charge. We find that, different flor yeast strains characterized by different degree of functional FLO11 are diversely affected in terms of biofilm formation and adhesion capacity when interact with different nitrogen sources. The positive role of the synthetic hexapeptide PAF26 in enhancing the biofilm formation was first discovered. On the contrary, cationic amino acids were able to inhibit biofilm formation and adhesion ability. Results together highlight on the involvement of the Flo11p in hydrophobic and electrostatic interactions and open to new investigations, addressed to the control of microbial adhesion and biofilm formation.