Taxonomy, Diversity, and Typing of Brewing Yeasts
José Paulo Sampaio, Ana Pontes, Diego Libkind and Mathias Hutzler
from: Brewing Microbiology: Current Research, Omics and Microbial Ecology (Edited by: Nicholas A. Bokulich and Charles W. Bamforth). Caister Academic Press, U.K. (2017) Pages: 85-118.
The taxonomy and systematics of brewing yeasts have been a matter of debate and controversy since the early days of microbiology in the 1800´s, when Saccharomyces cerevisiae and Saccharomyces carlsbergensis were first cultivated. The turbulent history of beer yeast systematics epitomizes the endeavours of yeast taxonomy since its origins when researchers used morphological characters and physiological traits to distinguish and classify species. The molecular revolution initiated in the 1980's exposed limitations of phenotypic methods, revealing numerous species synonyms and misclassifications. Today, DNA sequence data provide the means for accurate species identifications, strain typing, and phylogenetic classifications. Progress in the scientific knowledge of beer yeasts was also delayed by another level of complexity, which included inter-species hybridizations occurring in the brewing environment. Inter-species hybridizations created a plethora of chimeric genomes that could only be completely resolved when genomics entered the scene in the last two decades. Indeed, many key beer genotypes like S. pastorianus, the lager yeast, and S. bayanus, a beer contaminant, are complex multi-Saccharomyces species hybrids whose life history and ancestry are only now being revealed. Recently, a combination of novel genome sequencing approaches and microbial ecology studies solved decades-long disputes and revealed the wild genetic stocks of domesticated beer lineages. Here, we give an historical perspective of brewer's yeast taxonomy including also non-Saccharomyces yeast species and review available phenotypic and genetic-based typing methods for species and strain discrimination read more ...