The yeast Saccharomyces cerevisiae has been used in human food and drink production for more than 9,000 years. Domesticated yeast strains, such as those used in wineries, have been known to be dispersed into the environment, but the exact mechanism for this spread was unknown, as was how yeast spend the winters in the wild, without ripe fruits to ferment. Birds and insects have previously been proposed as natural reservoirs for yeast, but yeast cells have been found to survive less than a day in bird guts, and insects often don't live long enough themselves to be effective winter homes. But new research reveals that the queens of social wasps do accommodate S. cerevisiae during the off season. These insects overwinter as adults and pass on the contents of their guts, including yeast cells, to their young during feeding in the spring.
The discovery was made after researchers isolated yeast cells from wasps of wine-producing regions of Italy across all four seasons, and found they have a near-constant concentration of yeast in their guts, suggesting an "intimate and continuing relationship between these organisms," according to the authors of the study, published today (July 30) in Proceedings of the National Academy of Sciences.
The isolated yeast strains from the guts of the wasps closely matched isolates from wines and both commercial and wild local grapes, suggesting that wasps picked up their yeast commensals from both natural and industrial situations, and facilitate flow between the two sources. Yeast isolates from wasps also matched strains found in bread, African beers, and scientific laboratories, suggesting wasps aren't picky about what yeast they carry, and that wasps facilitate a continuous exchange of yeast strains within the local environment.
“The role of wasps in maintaining yeast cells during the winter and disseminating them before, during, and after the grape harvest ?lls the gap left by previous ?ndings indicating a yeast ?ow between the winery and the vineyard,” the authors wrote.