Mold as pets

10 000 years ago people started to domesticate animals and plants. It is very easy to come up with examples: dogs and cats as pets, sheep, cows, pigs, turkeys, wheat, and peas as food sources, horses, donkeys, and camels as working or draft animals, and cotton as a source of fiber. However, there exists another group of domesticated organisms that probably won’t come to your mind when you hear the word “domestication”, even though you see it everywhere. Do you ever go out to a bar or a nice restaurant, or maybe visit a sushi place? In every one of these places, you meet some domesticated microbial species. The yeast gives us beer and bread, certain bacteria help to make wine, and Koji mold is used in soy sauce production.

Let us look at one specific mold that evolved to be our pet. It is P. roqueforti, it is a mold fungus that is used for blue-veined cheese production, so let’s call it “cheese mold”. The scientists got strains of “cheese mold” from different types of blue-veined cheese and from silage, lumber, and spoiled foods. They divided strains into 4 genetic-related groups: 2 not connected to cheese and 2 “cheese-type”. Two cheese ones were named “Roquefort” and “non-Roquefort”. I find their choice of name to be quite creative. Their names are quite transparent about what they stand for: the type of mold that has been used to make original Roquefort shared by several regional farms, and the type used in cheese industrial production for other blue-veined cheese sorts, like Gorgonzola.

The purpose of the study was to describe the history of P. roqueforti domestication and humans’ influence on “cheese mold”. For that, the researchers need a sample of wild P. roqueforti, which hasn’t been discovered yet. However, they could say that two independent acts of domestication took place, one for “non-Roquefort” and one for “Roquefort”. Two “cheese-type” groups were also compared, and it turned out that “Roquefort” has fewer traits that are important for “cheese mold”. I was quite surprised by this. For example, compared to industrial molds used, “Roquefort” slowly grows on cheese, doesn’t tolerate high salt amounts (salt is used as cheese preservative), and it lacks traits necessary for aroma production, which is an essential blue-veined cheese characteristic. The researchers suggested two explanations for that. The first says that “roquefort” type of “cheese mold” was actually adapting to live not on cheese, but on bread. Sometimes there are happy accidents! It is based on the fact that the samples of mold used for further production were preserved and grown on bread. The second hypothesis explains the slow pace of growth. The farmers chose slow-growing mold over fast-growing intentionally. Why? This particular sort of cheese is made from ewe’s milk, which is available only from February to July, and there was no good way to store milk or cheese for half of the year. So slow-growing mold allowed the cheese to get ready to eat in a longer time after having it in milk form than a faster-growing mold would have. If you’re anything like me eating cheese year-round is really important, so its awesome that farmers figured this out.

Compared to researching animals and plants, it is more difficult to investigate the history of microbes. However, the thing that will help is the discovery of the wild strain of P. roqueforti. This will provide scientists with the material to compare domesticated strains with, so they will be able to tell us more about their histories.

Dumas, Emilie, et al. “Independent Domestication Events in the Blue‐Cheese Fungus Penicillium Roqueforti.” Molecular Ecology, 3 Feb. 2020, 10.1111/mec.15359.