Microbiome Thieves

Some gut bacteria in steal essential nutrients from our bodies

As humans, we are never truly alone. Living inside our organs are millions of bacteria, collectively referred to as our microbiome, that help us carry out essential life processes. The highest concentration of these bacteria are found in our small and large intestines, where they help us digest our food. While we have a mutually beneficial relationship with most of these bacteria—they aid our digestion and receive nutrients in return—it seems that some of these organisms are actually doing us more harm than good.

Researchers at the Yale Microbial Sciences Institute have discovered that some bacteria in our gut are actually stealing an essential nutrient, vitamin B12, away from us. Vitamin B12 is important because it helps keep our nerve and heart cells healthy and helps our bodies make DNA.

To our great surprise, we found that many members of our microbiota decorate their cell exteriors with proteins called BtuG that grab onto vitamin B12 with extraordinary binding strength,” said Aaron Wexler, lead author on the study, in a story published by Yale’s West Campus in September 2018. The study was conducted in the laboratory of Andrew Goodman, Associate Professor of Microbial Pathogenesis at the Yale School of Medicine.

The study found that Bacteroides, a type of bacteria that live in our gut, have genes that encode a surface molecule, BtuG, that helps transport vitamin B12 into their cells. According to the results of the study, BtuG binds vitamin B12 in the large intestine by removing an important protein that transports B12 in our bodies, suggesting that these bacteria prevent the absorption of vitamin B12 into our bloodstream.

When the researchers implanted bacteria with and without BtuG on their surface into the intestines of mice, the bacteria with BtuG rapidly exceeded the ability of those without BtuG to steal vitamin B12 away from the digestive tract. This indicates that bacteria with these proteins are better at taking away nutrients from us than those without them. 

Clearly, not all of the organisms that call our bodies home are paying their dues. Future research will be needed to elucidate the role that these bacteria play in our bodies and just how far their impact extends.