According to a team of researchers from the University of Leuven (Belgium) led by Kevin Verstrepen, the fruit fly ( Drosophila melanogaster ) is irresistibly attracted by the aroma given off by beer yeast ( Saccharomyces cerevisiae ), so that if the fungus stops emitting its scent, the insect no longer approaches.
The results of this study suggest that the odor emitted by this and other microorganisms seeks to attract insects to disperse their reproductive cells in the environment. “Two seemingly unrelated species have developed a complex symbiosis based on odor: the fly feeds on the yeast and the yeast benefits from the means of transport offered by the insect for reproductive purposes,” says Verstrepen.
Researchers claim that this type of symbiosis occurs frequently in nature . For many microbes, moving in the environment is complicated, so they have to attract other living beings, preferably with legs or wings. It seems feasible that the aroma that bacteria and fungi produce in foods like cheese is a tactic to attract insects.
The idea for the research came about by accident, when several flies escaped into the laboratory and darted towards a flask with a very odorous yeast culture, while they did not go near another flask containing a mutant yeast strain that was he had removed the scent gene. Now, the team from the University of Leuven has confirmed this by manipulating the ATF1 gene in yeast, responsible for the fruity smell. When it is deactivated, the fungus does not emit the smell and the flies do not come.
Experts acknowledge that it is not easy to show that the gene has evolved specifically to promote its reproduction, but they affirm that “it is tempting to speculate on this possibility given that several studies demonstrate the symbiosis between yeast and flying insects such as fruit flies.”
After experimenting with different varieties of yeast, experts have found that most produce fruity aromatic compounds. They have also confirmed that these substances do not adversely affect food . Their concentration is very small, but due to their purity they affect the aroma of fermented products.
