Genomic insights into the variable nitrate assimilation potential of Brettanomyces bruxellensis. Brettanomyces bruxellensis

The yeast Brettanomyces bruxellensis is well adapted to a range of industrial fermentative ecosystems, including those encountered in the production of alcoholic beverages and bioethanol. B. bruxellensis and S. cerevisiae have convergently evolved phenotypes that are useful for survival and competitiveness in alcoholic fermentations. However, it is in the nutrient-sparse, post-fermentative environment where B. bruxellensis is particularly suited, in part due its ability to utilise alternate carbon and nitrogen sources such as chitin, mannose, lactose and nitrate. Despite the fact that nitrate assimilation has been shown to confer a distinct competitive growth advantage relative to S. cerevisiae, B. bruxellensis displays intra-specific variation in nitrate assimilation potential, with many strains not able to utilise this source of nitrogen. In order to provide insight into this complex interplay between gene and environment, 41 isolates of Brettanomyces have been assessed at the phenotypic and genetic level for nitrate utilisation. Several nitrate-utilisation phenotypes were observed that correlated with specific genetic backgrounds, including the characterisation of a stable phenotypic switch in nitrate utilisation potential that occurs at low frequency in specific isolate populations.