Abstract
BackgroundOenococcus oeni, a member of the lactic acid bacteria, is one of a limited number of microorganisms that not only survive, but actively proliferate in wine. It is also unusual as, unlike the majority of bacteria present in wine, it is beneficial to wine quality rather than causing spoilage. These benefits are realised primarily through catalysing malolactic fermentation, but also through imparting other positive sensory properties. However, many of these industrially-important secondary attributes have been shown to be strain-dependent and their genetic basis it yet to be determined.ResultsIn order to investigate the scale and scope of genetic variation in O. oeni, we have performed whole-genome sequencing on eleven strains of this bacterium, bringing the total number of strains for which genome sequences are available to fourteen. While any single strain of O. oeni was shown to contain around 1800 protein-coding genes, in-depth comparative annotation based on genomic synteny and protein orthology identified over 2800 orthologous open reading frames that comprise the pan genome of this species, and less than 1200 genes that make up the conserved genomic core present in all of the strains. The expansion of the pan genome relative to the coding potential of individual strains was shown to be due to the varied presence and location of multiple distinct bacteriophage sequences and also in various metabolic functions with potential impacts on the industrial performance of this species, including cell wall exopolysaccharide biosynthesis, sugar transport and utilisation and amino acid biosynthesis.ConclusionsBy providing a large cohort of sequenced strains, this study provides a broad insight into the genetic variation present within O. oeni. This data is vital to understanding and harnessing the phenotypic variation present in this economically-important species.
Highlights
Oenococcus oeni, a member of the lactic acid bacteria, is one of a limited number of microorganisms that survive, but actively proliferate in wine
O. oeni is present at extremely-low to undetectable levels on intact grapes or in the general environment, with wine seemingly representing the exclusive niche of this bacterium, despite the seasonal nature of wine production [1,2,3]
It is fortunate that O. oeni provides positive attributes with regard to wine quality, as the majority of other wine-associated bacterial species are linked with spoilage [4]
Summary
Oenococcus oeni, a member of the lactic acid bacteria, is one of a limited number of microorganisms that survive, but actively proliferate in wine It is unusual as, unlike the majority of bacteria present in wine, it is beneficial to wine quality rather than causing spoilage. These benefits are realised primarily through catalysing malolactic fermentation, and through imparting other positive sensory properties. Like many fermented foods and beverages, wine represents a historical method of nutrient preservation that relies on suppressing the growth of spoilage microorganisms in order to provide long-term storage In finished wine, it is the physiochemical combination of high levels of ethanol and sulfur dioxide, scarcity of “preferred” nutrient sources and low pH that combine to produce a harsh environment in which all but a small number of microorganisms can proliferate. In addition to performing MLF, there is evidence that the growth of O. oeni in wine impacts on flavor, aroma and mouth-feel in a strain-specific manner [6,7,8]
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