Blue Cheese Has Turned Some Molds Into Evolutionary Wonders

What makes blue cheese the putrid, deliciously sumptuous foodstuff that it is?

Well—we are sorry to report—a lot of it has to do with mold. The delectably-pungent-but-fetid stuff is made by applying mold to milk. Roquefort? Its recipe is as follows: put a mold called Penicillian roqueforti on curds. Camembert? That starts with Penicillium camemberti. (And yes, penicillin, the antibiotic, comes from a similar fungi.) The Camembert rind, you may not really want to know, is a solid hunk of mold.

But as it turns out, the mold that makes blue cheese is some pretty amazing stuff. This week, Dr. Ricardo C. Rodríguez de la Vega—possibly the best-named scientist ever—and colleagues published a study on blue cheese molds in the journal Current Biology. They report that cheesemakers have—unintentionally—sped up the evolution of molds in ways that one biologist describes as "amazing." We're talking stunning genetic mutations and mashups of DNA from several species, creating molds that are essentially evolutionary outliers.

Dr. Rodríguez de la Vega and his colleagues set out to discover how mold species have changed thanks to cheesemaking. The scientists took ten species of the Penicillium mold and sequenced their genomes. Six of the mold species grew on milk—as in the cheesemaking process—and four were never found in cheese. The scientists were able to create an evolutionary tree going back to the common ancestor of all ten mold species, and at the top was a wild mold that lived on earth millions of years ago.

Here's the weird thing they found: Over time, the mold genes adapted and changed in unexpected ways. Some of the mold species—the ones used for cheese—had large swaths of foreign DNA in them. In other words, the mold contained DNA that came from other species entirely.

Eureka! The scientists had found that molds used in cheesemaking engaged in something called horizontal gene transfer. That's when an organism incorporates a chunk of foreign DNA into its own genome.

Turns out the molds that are used to make cheese love this horizontal gene transfer business. According to the New York Times, "This DNA has been jumping between species within the past few centuries, the French scientists report—probably as a direct result of cheesemaking."

The scientists even got to name the chunks of DNA that transferred between species. The biggest chunk of DNA transferred to the mold is now called "Wallaby"—it contains 250 genes. The second biggest, called "CheesyTer," contains about 60 genes.

Evidently, neither Wallaby nor CheesyTer appeared in non-cheesemaking mold. So, the scientists realized, the process of cheesemaking was having an unprecedented effect on the evolution of mold. And the selection of genes appears to facilitate cheesemaking; for instance, CheesyTer has a gene that allows molds to break down lactose, a form of sugar found in milk. The scientists believe that Wallaby and CheesyTer may have additional genes that help mold adapt to life in a block of blue.

Tatiana Giraud, a co-author of the study who works at the French National Centre for Scientific Research, told the Times that understanding this evolution "could give cheesemakers new ideas about how to produce new flavors."

It's nice to know that the mold world is cooperating—over several millennia, that is—with cheesemakers to make the stinky stuff we love to eat.