Changes

When ''P. damnosus'' lives together with ''Saccharomyces'', a chemical is produced by ''P. damnosus'' that essentially "turns on" the GAF+ gene in ''Saccharomyces''. Not only does ''Sacch'' then have the ability to ferment other sugars at the same time as glucose, but it produces less alcohol. Viability over time is also increased in ''Sacch'' cells that express this gene versus those that don't. In wild fermentation of grapes, the wild GAF+ ''Sacch'' strains thrived over the other types of fungi that were found on the wild grapes. This led the researchers of the referenced study to speculate that the GAF+ gene may play a role in preventing other fungi from thriving. It is thought that this creates benefits for both microorganisms, which are often found together in the wild during fermentation of fruit; the bacteria isn't killed by higher alcohol levels, and the yeast has a broader food source. Furthermore, once a ''Saccharomyces'' cell expresses the gene, it will continue to pass this gene onto it's offspring. In winemaking, this is the cause of arrested wine fermentations due to the lower amount of alcohol produced (in the referenced study, the GAF- ''Sacch'' cells fermented grape must into a 12% ABV wine, and the GAF+ ''Sacch'' cells fermented the same wine must into an 8% ABV wine) <ref name="cross-kingdom"></ref>. However, the implications of this in sour beer brewing are much different and have yet to be explored scientifically.

==See Also==