Hypomyces lactifluorum is an unmistakable, sought after mycological find I have yet to encounter this calendar year. I have found other closely related Hypomyces species, but not the red-orange specimen commonly known as the lobster mushroom. This common name is a bit misleading, as Hypomyces lactifluorum isn’t a mushroom, but a parasitic ascomycete fungus that infects mushrooms. Eventually it forms a red-orange crust all over its host, resembling a shell of a cooked lobster. The species featured in today’s Fungi Friday specializes in parasitizing a handful of species from Russula and Lactarius genera. Many of the mushrooms the parasite can infect are not pursued by mushroom hunters until they do in fact become infected by H. lactifluorum. It might sound farfetched but the mycotrophic parasite actually changes the chemical composition of its host, thereby altering its texture and flavor profile.
H. lactifluorum occurs in ecosystems where its preferred host shows up. Mushrooms from these Russulaand Lactarius genera engage in ectomycorrhizal relationship with a diverse array of trees, including hardwoods and conifers. The ability to parasitize different fungal genera that engage in mycorrhizal relationships with a wide diversity of trees from around the world help explain this parasite’s global distribution. By looking through mushroomobserver.org you can easily find specimens recorded from nearly every corner of the Earth. Some mycologists believe that it only occurs in North America, and that other observations may be new species altogether. I wouldn’t be surprised if this was true given the current track record of fungal taxonomy. New Hypomyces are found every year, adding to the immense fungal kingdom we already have.
What I was most intrigued about was how this fungus shifts non-poisonous but not sought-after mushrooms into delectable, highly regarded forest floor treats. Most professional foragers leave the Russula species they find behind, because of their lack of flavor and their fragile structure. But once infected by H. lactifluorum, they become choice edibles. I wanted to know more about this, so I scoured the scientific literature, searching for articles describing the molecular transformation of its host mushroom. Luckily, just this year, researchers Genevieve Laperriere, Isabel Desgagné-Penix and Hugo Germain were wondering the same thing!
These Canadian scientists focused their efforts on describing the metabolic transformation of Russula brevipes by Hypomyces lactifluorum. In their neck of the woods, along with the North-eastern United stated, the main host of the fungal parasite is Russula brevipes. The molecular transformations are most likely different with each fungal host, so for simplicities sake, they just concentrated on Russula brevipes. The strongest part of their study was how they analyzed the host. They didn’t just look at the genes and chemical makeup of Russula brevipes before and after infection but observed the changes of these two features throughout the infection process.
Interestingly, they found the DNA of both species changes both spatially and temporally. Spatially, there was little DNA of R. brevipes in the red-orange margin dominated by H. lactifluorum stroma and spore filled perithecia. With increased distance from the red-orange margin, more R. brevipes DNA was obtained, with the inner-most part of the fruiting body having the highest quantity of R. brevipes DNA. Though, this changed throughout the infection process, as DNA from R. brevipes decreased, eventually being marginally replaced with H. lactifluorum DNA.
These changes in DNA quantity doesn’t adequately describe the alteration in flavor profile. Lobster mushrooms are choice edibles because the parasite chemically alters the fungal tissue. Although the sliced fruiting body appears the same as R. brevipes before infection, (minus the red-orange margin) its chemical constituents become significantly altered. The metabolomic analysis conducted be the researchers showed that after R. brevipes becomes fully parasitized, lipid content increased by nearly 30%, while terpenoids decreased by 30%. Additionally, the percentage of amino acids increased by a factor of 10! Chemically broken down like this, we get to see why the lobster mushrooms become choice edibles. The may look like their host, but they certainly are not the same tissue, nor the same flavor.
Lobster mushrooms represent a fascinating example of parasitism as well as food science. Forest floor parasites like H. lactifluorum can radically alter the chemical composition of its host without having our palate in mind. It is by random chance that our own human taste buds are pleased by the way H. lactifluorum chemically alters R. brevipes tissue. Not only are the chemicals altered in the fruiting body, but the spatial and temporal position of the DNA in the two species as well. Hopefully after reading this, you too will be looking for lobster in the woods, from both a scientific and culinary standpoint.