Bifidobacterium longum. Source: The VisualMD
By Sara Specht
It’s the same old story: while exploring the wilds of a jungle, a scientist stumbles upon a miracle cure. Only this jungle is much closer to home—the flora of the human gut. And this stunning discovery just might bring a super-preservative to local grocery store shelves.
It all started because Daniel O’Sullivan, a researcher in the Department of Food Science and Nutrition, wanted to know why Probiotic bifidobacteria seem to become toothless when they are fermented for use in foods like yogurt. Probiotics naturally reside in the flora of the human large intestine and help fight harmful bacteria to keep the gut healthy. O’Sullivan mapped the genome of a human-grown sample of Probiotic Bifidobacterium longum and discovered that it was actually bigger than a lab-cultivated specimen.
“They say the lion rules the jungle, and it’s very well suited to doing that. In evolutionary terms, if you take the lion out and raise it in a house, it becomes a pussycat,” O’Sullivan says. “That’s what we saw happen when we took the Bifidobacteria out of the jungle in the gut and put it in a nice pure culture and pampered it. It lost its claws.”
In this case, the Bifidobacteria loses chunks of DNA that it no longer needs to compete in a pure culture. One of those lost pieces is a previously unknown anti-microbial lantibiotic called bisin. Lantibiotics naturally combat foodborne pathogens, and some are commonly used as food preservatives. But while other lantibiotics kill only gram-positive bacteria, bisin is the first discovered that can protect against both those and gram-negative bacteria, like E. coli and Salmonella: the sources of over half of the United States’ food recalls every year. Bisin apparently fights these bacteria so effectively that treated foods could last almost indefinitely.
As a naturally occurring peptide, bisin doesn’t pose the health risks that chemical food preservatives can, and it has already been characterized as safe for consumption. And since bisin is chemically related to a lantibiotic preservative already in widespread use, nisin, O’Sullivan says the processes are already in place to apply it to food ingredients.
Professor Dan O´Sullivan in his laboratory.
There is one last barrier to getting bisin onto the market—getting bifidobacteria to produce it anywhere other than the intestinal jungle. O’Sullivan is back in the lab trying to understand on a molecular level how to induce bisin production in a laboratory or industrial fermenter. He says once they learn how to flip that switch, it will be ready to be licensed and put on the market.
“This is a very stubborn bug,” O’Sullivan says. “We know how to switch on production of bisin, but then it switches itself off. If we can get rid of that stubborn off switch, bisin has a lot of potential as an antimicrobial tool for food safety and maybe pharmaceutical applications.”