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Food manufacturers often add preservatives to food products to keep them fresh. The purpose of these preservatives is to kill microorganisms that can break down and destroy food. Common additives such as sugar, salt, vinegar, and alcohol have been used as preservatives for centuries, but modern food labels now reveal more unfamiliar ingredients such as sodium benzoate, calcium propionate, and potassium sorbate.
Bacteria produce chemicals called bacteriocins to kill microbial competitors. These chemicals can act as natural preservatives by killing potentially dangerous pathogens in food. Lanthipeptides are a class of bacteriocins with particularly potent antimicrobial properties that are widely used by the food industry and are known as "lantibiotics" (a scientific combination of lanthipeptides and antibiotics).
However, despite their widespread use, little is known about how these antibiotics affect the gut microbiome of people who consume them in food. The microbes in the gut live in a delicate balance, and symbiotic bacteria provide vital benefits to the body by breaking down nutrients, producing metabolites, and importantly, protecting against pathogens. If too many commensal bacteria are indiscriminately killed by antimicrobial food preservatives, opportunistic pathogens may take their place and wreak havoc – an outcome that is no better than eating contaminated food in the first place.
A new study published in ACS Chemical Biology by scientists at the University of Chicago has found that the most common class of antibiotics has a powerful effect on both pathogens and commensal gut bacteria that maintain health.
Streptococcin lactis a popular antibiotic used in everything from beer and sausages to cheese and dips. It is produced by bacteria that live in the mammary glands of dairy cows, but microbes in the human gut also produce similar antibiotics. Dr. Zhenrun "Jerry" Zhang is Donald F., University of ChicagoSteiner, professor of medicine and a postdoctoral scholar in the laboratory of Eric Pamer, MD, director of the Duchossois Family Institute, wanted to study the effects of this naturally occurring antibiotic on commensal gut bacteria.
Essentially, streptococcin lactis an antibiotic that has been added to our food for a long time, but how it affects our gut microbes has not been well studied," Zhang said. "Although it may be very effective in preventing food contamination, it may also have a greater impact on our human gut microbe.
He and his colleagues dug into a public database of the human gut bacterial genome and identified the genes that produced six different gut-derived antibiotics that were very similar to streptococcal lactis peptides, four of which were new. Then, with Richard E., University of Illinois at Urbana-ChampaignHeckert Professor of Chemistry Wilfred ADr. Van der Donk collaborated, and they produced versions of these antibiotics to test their effects on pathogens and commensal gut bacteria. Researchers have found that while different antibiotics have different effects, they can kill pathogens and commensal bacteria.
This study was one of the first to show that intestinal commensal bacteria are susceptible to antibiotics and sometimes more sensitive than pathogens," Zhang said. "Given the current levels of antibiotics in food, it's likely that they will also affect our gut health.
Zhang and his team also studied the structure of peptides in antibiotics to better understand their activity to learn how to take advantage of their antimicrobial properties. For example, in another study, the Pamer lab showed that a consortium of four microbes, including one that produces antibiotics, helped protect mice from antibiotic-resistant enterococcal infections. They are also studying the flow of antibiotic resistance genes in different populations to better understand how the bacteria colonize the gut under different conditions and diets.
It seems that antibiotics and antibiotic-producing bacteria are not always good for health, so we are looking for ways to combat potential adverse effects while taking advantage of their more beneficial antimicrobial properties," Zhang said.
More information: zhenrun jZhang et al., Activity of gut-derived streptococcin-like antibiotics against human intestinal pathogens and commensals, ACS Chemical Biology (2024). doi： 10.1021/acschembio.3c00577