An evolutionarily conserved prion-like element converts wild fungi from metabolic specialists to generalists.

[GAR(+)] is a protein-based element of inheritance that allows yeast (Saccharomyces cerevisiae) to circumvent a hallmark of their biology: extreme metabolic specialization for glucose fermentation. When glucose is present, yeast will not use other carbon sources. [GAR(+)] allows cells to circumvent this "glucose repression." [GAR(+)] is induced in yeast by a factor secreted by bacteria inhabiting their environment. We report that de novo rates of [GAR(+)] appearance correlate with the yeast's ecological niche. Evolutionarily distant fungi possess similar epigenetic elements that are also induced by bacteria. As expected for a mechanism whose adaptive value originates from the selective pressures of life in biological communities, the ability of bacteria to induce [GAR(+)] and the ability of yeast to respond to bacterial signals have been extinguished repeatedly during the extended monoculture of domestication. Thus, [GAR(+)] is a broadly conserved adaptive strategy that links environmental and social cues to heritable changes in metabolism.