Credit: Image by Markéta Machová from Pixabay

Reviewed by Jatin Kumar (Biotech communicator)

A team of scientists led by Stephen Withers at the University of British Columbia in Vancouver, Canada discovered certain bacterial enzymes from the gut bacterium Flavonifractor plautii, that converts Type A blood group into universal Type O blood, by removing surface molecules called Antigens, responsible for determining blood types. The paper is published in Nature Microbiology in 2019.

Type A, B and AB blood groups have their own kinds of antigens (which may be sugars or proteins that are attached to different parts of the membrane of Red blood cells) that must be matched during a blood transfusion. But Type O blood group doesn’t have such antigen, so no need to be matched hence called Universal donor blood group.

Scientists were demonstrated such conversion using enzymes way back in 1982, for Type B blood group which was easier to convert, but a huge amount of such enzymes were required. Then in 2007, scientists discovered two bacterial enzymes that could remove A and B antigens from RBCs but were still not efficient or selective enough to work in whole blood. To make this viable, they were required to make the enzymes more effective.

After four years of trying to improve such enzymes, Withers and his team decided to work on human gut bacteria that feed on sugar-protein combos called mucins, which is similar to the blood type defining antigens on RBCs. They collected human stool sample and isolated its DNA that includes genes, encoding mucin-digesting enzymes. After fragmenting the DNA, introduced into Escherichia coli and monitored the production of proteins having the ability to remove A-defining sugars.

At first, they didn’t find any positive result, but when they tested two of the resulting enzymes at a time, by ligating substances that glow when sugar gets removed, they got the positive result and the enzymes also worked in human blood. Now even tiny amounts of enzymes could remove the type-A sugars from a unit of type-A blood, which makes this finding very promising in terms of practical utility. But need to make sure that the microbial enzymes have not altered anything else on the RBCs, which could be a problem.

For now, scientists are only focussed on converting type-A, as is more common than type-B blood. Thousands of patients die every year across all over the world due to unavailability of matched blood type and universal donor Type-O blood group. Having the ability to transform type A to type O, Withers said, “it would broaden our supply of blood and ease these shortages.”


Research article: “An enzymatic pathway in the human gut microbiome that converts A to universal O type blood” – Published in Nature Microbiology