Studying cheese reveals how microbes interact

Microbiologist Rachel Dutton's work focuses on bacterial ecosystems in rinds

selection of cheeses

SAY CHEESE Fungi and bacteria shape the distinctive characters of a wide range of cheeses.

Floortje/iStockphoto

Rachel Dutton’s research is cheesy, by design. The microbiologist at the University of California, San Diego uses cheese rinds to study how microbes form communities.

Dutton, who has a long-standing interest in how bacteria and other microbes interact, got the inspiration for her studies several years ago while visiting the Marine Biological Laboratory in Woods Hole, Mass. In the salt marshes there, multiple species of bacteria, archaea and other microbes were growing in thick, many-layered mats. They would have been perfect for studying microbes in groups. Except for one thing: Many organisms that thrive in those mats won’t grow in captivity. Dutton needed a microbe community that she could pick apart, manipulate and reconstruct in the lab.

Bacteria and fungi, like the Penicillium camemberti shown here, work together to give cheeses their texture and flavor. R. Dutton/U.C. San Diego
The solution came with a round of cheese from France. Sliced open, its rind reminded Dutton of the microbial mats on the coastal salt marshes. “I took a piece of cheese into the lab and put it under the microscope,” she says. “Everything I was looking for in a microbial community was present.”

Dutton and colleagues did genetic analyses of 137 cheeses from 10 countries and identified 24 genera of bacteria and fungi that are common in cheeses and will grow in the lab, the team reported in 2014 in the journal Cell.

By sampling a Vermont cheese as it aged over 63 days, the group also discovered that rind communities don’t form instantly.

Dutton and other members of her lab talk about their cheese research in Cell.Cell Press

At the beginning, community members included Proteobacteria and Leuconostoc bacteria, plus candida yeast commonly found in raw milk. Within a week, Staphylococcus had overwhelmed the Proteobacteria. As the cheese ripened, Brevibacterium and Brachybacterium plus Penicillium and Scopulariopsis fungi became prominent inhabitants of the rind. That pattern held whenever those organisms congregated in a cheese in the lab.

Cheesemakers from Vermont taught Dutton how to ferment cheese curds and create her own lab version of a dry-aged cheddar. Although cheeses can have complex combinations of microbes — stinky cheeses have the most diverse mixes — Dutton’s lab crafts a more simplified rind using three types of fungi and four bacteria. The researchers grow the microbes in pairwise combinations to learn how they interact.

Microbiologist Rachel Dutton got the inspiration to study cheese when she realized that cheese rinds (left, a rind from a washed rind cheese) resemble microbial mats (right) from salt marshes and other locations. From left: R. Dutton; S.A. Cantrell/Front. Microbiol. 2013 (CC BY 3.0)

Studying cheeses and other fermented foods could teach scientists how microbial communities evolved in different places and lead to the creation of new, tastier and safer foods, Dutton and Benjamin Wolfe of Tufts University wrote last year in Cell.

There’s one drawback to the cheesy research: The lab has a ripe odor, Dutton says. “We look like a normal microbiology lab, but we don’t smell like one.”  

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