Brettanomyces bruxellensis population survey reveals a diploid-triploid complex structured according to substrate of isolation and geographical distribution

Marta Avramova,Paul Grbin,Marguerite Dols-Lafargue,Franck Salin,Alice Cibrario,Warren Albertin,Emmanuel Coton,Emilien Peltier,Monika Coton,Giuseppe Blaiotta,Joseph Schacherer,Isabelle Masneuf-Pomarede,Vittorio Capozzi,Giuseppe Spano,Chris Curtin

doi:10.1038/s41598-018-22580-7

Abstract

Brettanomyces bruxellensis is a unicellular fungus of increasing industrial and scientific interest over the past 15 years. Previous studies revealed high genotypic diversity amongst B. bruxellensis strains as well as strain-dependent phenotypic characteristics. Genomic assemblies revealed that some strains harbour triploid genomes and based upon prior genotyping it was inferred that a triploid population was widely dispersed across Australian wine regions. We performed an intraspecific diversity genotypic survey of 1488 B. bruxellensis isolates from 29 countries, 5 continents and 9 different fermentation niches. Using microsatellite analysis in combination with different statistical approaches, we demonstrate that the studied population is structured according to ploidy level, substrate of isolation and geographical origin of the strains, underlying the relative importance of each factor. We found that geographical origin has a different contribution to the population structure according to the substrate of origin, suggesting an anthropic influence on the spatial biodiversity of this microorganism of industrial interest. The observed clustering was correlated to variable stress response, as strains from different groups displayed variation in tolerance to the wine preservative sulfur dioxide (SO2). The potential contribution of the triploid state for adaptation to industrial fermentations and dissemination of the species B. bruxellensis is discussed.

Highlights

Brettanomyces bruxellensis is a unicellular fungus of increasing industrial and scientific interest over the past 15 years
B. bruxellensis is an essential contributor to the elaboration of some specialty Belgian and American beers, which are the result of complex spontaneous fermentations performed by various genera of bacteria and yeasts[7,8]
B. bruxellensis was reported to be a common contaminant in bioethanol production plants[12,13], and under the right conditions can take the place of the industrial Saccharomyces cerevisiae strains and perform molasses fermentation[13]

Summary

Introduction

Brettanomyces bruxellensis is a unicellular fungus of increasing industrial and scientific interest over the past 15 years. Various studies highlighted great phenotypic diversity of B. bruxellensis regarding growth capacity[14,15,16,17,18,19], sugar metabolism[20,21,22,23], nitrogen source utilisation[21,24], volatile phenols production[5,14,18,20,23,25,26], behaviour in viable but not cultivable state[27], and response to abiotic factors like temperature[20,28], pH20,29, oxygen availability[30,31,32] and sulfur dioxide (SO2)[20,23,28,33,34,35] This phenotypic variation makes it difficult to predict the spoilage potential of B. bruxellensis and is a major concern for winemakers. A striking example is a study of 41 B. bruxellensis wine isolates from Australia showing that the most common genotype (92% of studied isolates) was correlated with SO2 tolerance, suggesting that SO2 usage patterns may have created a selective pressure on this population[34]

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Results

Conclusion