Nutty, sweet smell with a distinctive taste—this is a typical culinary description of lobster mushrooms, prized by amateur cooks and chefs alike. Yet behind the tasty morsels is a hostile and unforgiving microbial world. The parasitic fungus Hypomyces lactifluorum infects and colonizes the mushroom Russula brevipes—white, bitter and non-edible—and transforms it into the orange, culinary wonder known as the lobster mushroom. In a pioneering study in Botany, combining molecular biology and biochemistry, Genevieve Laperriere and colleagues from the University of Quebec at Trois-Rivières track the infection process and colonization of Russula brevipes by the parasitic fungus Hypomyces lactifluorum, and decipher the complex taste profile of lobster mushrooms resulting from that infection. Their work will help strengthen the large-scale industrial use and commercialization of lobster mushrooms in Canada, one of the world’s largest exporters of fresh mushrooms with an industry value of $1 billion.
Laperriere et al. extracted DNA from infected (edible) and non-infected (non-edible) mushrooms collected from various sites around Quebec. They found that the infected and edible lobster mushroom mostly contains the DNA of the parasitic fungus with only trace amounts of Russula brevipes DNA.
Laperriere and his team also measured intermediate products of chemical reactions, or metabolites, in infected and non-infected mushrooms. Metabolites help determine how fungi look and taste, and whether they are fit to eat. They found that through the course of its infection, the parasitic fungus completely alters the diversity and amount of metabolites in Russula brevipes.
For example, terpenes, small chemical products synthesized by Russula brevipes, are completely absent from lobster mushrooms infected by the parasitic fungus. Russula brevipes produces these chemicals partly for its protection and defense against infection. As Laperriere and his team found, the complete absence of terpenes from lobster mushrooms indicates a successful infection by the parasitic fungus. Interestingly, some varieties of terpenes are responsible for the pungent and bitter taste of Russula brevipes. Laperriere and his team speculate that during the course of infection, these chemicals get converted into other more flavourful compounds, making lobster mushrooms more palatable.