In heritable mutualisms, hosts pass on beneficial symbionts between generations. The origin of this relationship though, is often antagonistic and the parasite first needs to secure its own transmission before working with the host. Using the mutualistic relationship between the plant pathogenic fungus Rhizopus microsporus (Rm) and Burkholderia endobacteria, JGI and Cornell University researchers reported on how the antagonistic-to-mutualistic transition occurs in Nature Communications. The team found that the oil-producing fungus is highly dependent on the Burkholderia endobacteria to proliferate both sexually and asexually. This dependence is consistent with the addiction model of mutualism evolution. Read more on the JGI website.