Characterization of Brettanomyces bruxellensis biofilm, a resistance strategy to persist in wine-related environments

Abstract

AIM: Biofilm is a resistance mechanism deployed by microorganisms to adapt to stresses, leading to their persistence in the environment. In the case of Brettanomyces bruxellensis, a wine spoilage yeast, knowledge about its capacity to form biofilm remains limited although this potential strategy could explain its recurring presence in cellars. In this study, we propose to investigate the capacity of strains of B. bruxellensis to form biofilm according to different conditions and to characterize its structure.

METHODS: Sixty-five isolates of B. bruxellensis were sampled from a cellar and discriminated into genetic groups by microsatellite analysis. The capacity of selected strains to adhere and form biofilm has been investigated in different conditions of media and supports, related to wine environment. The structure of the biofilm and its components were explored using several microscopic techniques as confocal laser scanning microscopy, electronic microscopy and epifluorescence microscopy.

RESULTS: Twelve strains among the 65 isolates were selected and have showed the capacity to form biofilm on polystyrene surface. Microscopic observations of the biofilm revealed microcolonies, filamentous cells and extracellular polymeric substances despite a small thickness. Then, the study of the impact of wine on B. bruxellensis biofilm revealed biofilm cell released and growth of these released biofilm cells, probable contamination source of the wine. Finally, for both planktonic and biofilm lifestyles in wine, a new chlamydospore-like element was observed for B. bruxellensis, described as a resistance form in other fungi.

CONCLUSIONS: This study validates the capacity of B. bruxellensis to form biofilm and highlights structural element of this mode of life. Moreover, an additional resistance strategy was suggested through the description of the chlamydospore-like elements. New insights into the persistence of B. bruxellensis during the winemaking process and in wineries have emerged.