yeast breeding
A worker hornet feeding on a grape in a Tuscan vineyard Stefano Turillazzi

Brewer's yeast, which is responsible for fermentation in wine, beer and bread, actually 'mates' inside the intestines of wasps, scientists have discovered. Furthermore, the Italian and Spanish researchers found that unrelated yeast strains would mate in the guts of wasps – suggesting they could provide a breeding ground for new combinations of yeast.

According to research published in the journal PNAS, the team said that despite the huge interest in the yeast species Saccharomyces cerevisiae, little is known about its lifestyle and, specifically, its mating behaviour. Previously it had been thought that unrelated strains of yeast did not mate, but recent evidence of hybridisation has suggested that this happens frequently. To find out more about the strain, the team used genetic analysis to look at its mating behaviour.

They found several unlikely hybrids, with crosses between brewer's yeast and wild strains generated in the intestine of social wasps. When specific yeast strains were introduced into wasp intestines, they found that unrelated strains would regularly mate. They also found that one wild yeast, Saccharomyces paradoxus, could only survive in the wasp gut if it mated with S cerevisiae.

"We show that the intestine of social wasps favours the mating of Saccharomyces strains by providing a succession of environmental conditions prompting sporulation and germination," they wrote, adding that the findings are significant because hybrid strains have been a source of several industrial yeasts used in making beer and wine.

"Taken together, these findings unveil the best hidden secret of yeast ecology, introducing the insect gut as an environmental alcove in which crosses occur, maintaining and generating the diversity of the ascomycetes."