Food manufacturers often add preservatives to food to keep them fresh. One of the main purposes of these preservatives is to kill microbes that could decompose the food and cause it to spoil. Common additives like sugar, salt, vinegar, and alcohol have been used as preservatives for centuries, but more modern food labels now list lesser-known chemicals such as sodium benzoate, calcium propionate, and potassium sorbate.
Bacteria produce chemicals called bacteriocins to kill microbial competitors. These chemicals can serve as natural preservatives by killing potentially harmful foodborne pathogens. Lanthipeptides, a class of bacteriocins with particularly potent antimicrobial properties, are commonly used in the food industry and are known as „lantibiotics“ (a scientific synonym for lanthipeptide and antibiotic).
However, little is known about how these lantibiotics affect the human gut microbiome when consumed through food. Microbes in the gut exist in a delicate balance, and commensal bacteria offer important benefits to the body by breaking down nutrients, producing metabolites, and – most importantly – protecting against pathogens. If too many commensals are killed off indiscriminately by antimicrobial food preservatives, opportunistic pathogenic bacteria could take their place and wreak havoc – a result that is no better than consuming contaminated food in the first place.
Effects on Good and Bad Bacteria
A new study published in ACS Chemical Biology by scientists at the University of Chicago found that one of the most common classes of lantibiotics has strong effects against both pathogens and the gut bacteria that keep us healthy.
Nisin is a popular lantibiotic used in everything from beer and sausage to cheese and dip sauces. It is produced by bacteria that live in the mammary glands of cows, but microbes in the human gut also produce similar lantibiotics. Zhenrun „Jerry“ Zhang, PhD, a postdoctoral researcher in the laboratory of Eric Pamer, MD, the Donald F. Steiner Professor of Medicine and Director of the Duchossois Family Institute at UChicago, wanted to investigate the effects of such naturally produced lantibiotics on commensal gut bacteria.
Nisin is essentially an antibiotic that has been added to our food for a long time, but its impact on our human gut microbes is not well studied. While it could be very effective in preventing food contamination, it could also have a more significant impact on our human gut microbes.“
Zhenrun „Jerry“ Zhang, PhD, Postdoctoral Researcher
He and his colleagues searched a public database of human gut bacterial genomes and identified genes for the production of six different gut-derived lantibiotics that closely resemble nisin, with four of them being newly discovered. They then, in collaboration with Wilfred A. van der Donk, PhD, the Richard E. Heckert Professor of Chemistry at the University of Illinois Urbana-Champaign, synthesized versions of these lantibiotics to test their effects on both pathogens and commensal gut bacteria. The researchers found that the different lantibiotics had varying effects, but each of them killed both pathogens and commensal bacteria.
„This study is one of the first to show that the gut flora is susceptible to lantibiotics and sometimes more so than pathogens,“ Zhang said. „Given the current prevalence of lantibiotics in food, it is very likely that they also have an impact on our gut health.“
Harnessing the Power of Lantibiotics
Zhang and his team also examined the structure of the peptides in the lantibiotics to better understand their activity and learn how to use their antimicrobial properties for good. For example, in another study, the Pamer lab showed that a consortium of four microbes, one of which produces lantibiotics, helps protect mice from antibiotic-resistant Enterococcus infections. They are also investigating the prevalence of lantibiotic-resistant genes in different populations to better understand how such bacteria can colonize the gut under different conditions and diets.
„It seems that lantibiotics and lantibiotic-producing bacteria are not always good for health. That’s why we are looking for ways to counteract their potential negative impact while still harnessing their beneficial antimicrobial properties,“ Zhang said.
Zhang, ZJ, et al. (2024). Activity of Human Gut-Derived Nisin-Like Lantibiotics against Human Gut Pathogens and Commensals. ACS Chemical Biology. doi.org/10.1021/acschembio.3c00577.