Scientists use cheese to study fungal antibiotics

See the microscopic power of cheese. Dairy has been a staple food for generations, but it’s also helping microbiologists better understand nature’s microbiomes. In a study published May 10 in the journal mBioa team of researchers used cheese rinds to demonstrate how fungal antibiotics can affect the development of microbiomes.

[Related: Beehives are the honeypot for a city’s microbial secrets.]

Metabolites produced by mushrooms can improve human health. Some secrete penicillin, which is then purified and used as an antibiotic. For this study, the scientists sought to better understand how fungi interact with the microbes living next to them in microbial communities, with a special focus on the relationship between fungi and bacteria.

“My lab is interested in how fungi shape the diversity of microbial communities where they live. “Fungi are widespread in many microbial ecosystems, from soils to our own bodies, but we know far less about their diversity and roles in microbiomes than the more widely studied bacteria,” said co-author and Tufts University microbiologist Benjamin Wolfe in statement. “To study the ecology of fungi and their interactions with bacteria, we use cheese rinds as a model microbial ecosystem to understand these fundamental biological questions.

Cheese rinds themselves are microbial communities that form on the surfaces of naturally aged cheeses such as brie, taleggio and some types of cheddar. As cheeses age, fuzzy and sometimes sticky layers of microbes form on the surface of the cheese. Microbes slowly decompose as the cheese ripens and grow on the surface to create the flavors and colors that give cheeses in the high-end section of the grocery store their more unique properties.

Wolff and his team began by investigating a cheese maker’s problem with mold spreading over the surface of the cheese and disrupting the normal development of the rind. This makes the cheese look like the rinds are disappearing when the mold invades their cheese cave. They collaborated with microbiologist Nancy Keller’s lab at the University of Wisconsin to find out what this mold is doing to the microbes in the bark and what chemicals the mold might be producing that destroys the bark.

Those researchers first deleted a gene (laeA) in Penicillin a mold that can control the expression of chemicals that fungi can release into the environment. These compounds are called specialized or secondary metabolites.

“We know that many fungi can produce metabolites that are antibiotics because we’ve used them as human medicines, but we know surprisingly little about how fungal antibiotics work in nature,” Wolff said. “Do fungi really use these compounds to kill other microbes? How do these antibiotics produced by fungi affect the development of bacterial communities? Added our normal and our laeA-deleted Penicillin to a community of cheese rind bacteria to see if deletion of laeA caused changes in the way the bacterial community developed.

[Related: You might be overusing hand sanitizer.]

When laeA was deleted, most of the antibacterial activity of Penicillin the mold was lost. This discovery helped the team narrow down the specific regions of the fungal genome that can produce antibacterial compounds. They narrowed it down to a class of compounds called pseudotins. Metabolites are produced by multiple species of fungi and can modulate the immune system, kill insects and inhibit bacteria.

The study showed that pseudotins can also control how the bacterial communities living with these fungi grow and develop. Pseurotins are highly antibacterial, meaning they inhibit some of the bacteria found in artisanal cheeses, including Staphylococcus, Brevibacterium, Brachybacteriumand Psychrobacter. This process caused a change in the microbiome composition of the cheese rind.

It also shows that antibiotics secreted by fungi can control how microbiomes develop, as metabolites are in other ecosystems, including the human microbiome and soil ecosystems. The team expects that these mechanisms of fungal-bacterial interactions are likely to be very widespread.

“Our results suggest that some nuisance mold species in artisanal cheeses can disrupt normal cheese development by administering antibiotics,” Wolff said. “These findings allow us to work with cheese makers to identify which molds are the bad ones and how to manage them in their cheese caves.” It also helps us appreciate that every time we eat artisanal cheese, we are consuming the metabolites that microbes use to compete and cooperate in communities.

Leave a Comment

Your email address will not be published. Required fields are marked *