What good are ____ ?
Fill in the blank with the objectionable life form of your choicemosquitoes,black flies,slugs,parasitic worms,unnamed things that are too squishy for words.
Although the question Why are we here? is much trumpeted as a human preoccupation,what most of us really want to know is Why are they here? And if they are nonhuman,science is pretty good at coming up with answers.
All those bacteria that live in and on us,and outnumber our own cells? They help our digestion,and fight off bad bacteria. Bats? They eat insects. And in the latest news,researchers have found that European hornets and paper wasps,which pack a sting nasty enough to make anyone question their reason for being,provide a cozy winter home in their guts for one of humanitys most important microbiological buddies: yeast.
The yeast in question is Saccharomyces cerevisiae,sometimes called bakers yeast,but particularly important in the making of wine,as well as beer and bread. Humans have been benefiting from S. cerevisiae for at least 9,000 years,but we encounter it mainly in the warmer monthson grapes,or in bakeries.
A group of scientists in Italy and France decided to investigate one possibility,social wasps,including European hornets and paper wasps. These insects were known to feed on grapes and to harbour varieties of yeast in their guts. So the researchers,including Irene Stefanini,Leonardo Dapporto and Duccio Cavalieri,all of the University of Florence,conducted several tests on the insects.
The wasps did have S. cerevisiae in their guts,and whats more they had different strains connected to the areas where they livedperhaps part of the reason wines from different places have different flavours. And yeast does survive over the winter in the guts of the queens who found new colonies in the spring,feeding regurgitated food to the young.
Thus the young wasps or hornets would acquire yeast from the colony founder and spread it to ripe grapes when feeding. When the harvest was over,the wasps would bring with them yeast that had been living in the vineyards. And if in the process of developing winemaking traditions we developed new strains of yeast,the hornets could keep them alive during the winter.
Its a heartwarming ecological story,and the report on the wasps,in The Proceedings of the National Academy of Sciences,makes one wonder about what other silent partners are out there whose activities have yet to be uncovered.