Using gut bacteria, scientists have come one step closer to "universal" donor blood, where any blood type can donate to any other. While people with type O blood are already universal donors ...

Around 50% of people naturally have type O or "universal" blood, but those with type A, type B and the rarer type AB blood can currently only give and receive blood from their own group.

O- is a universal donor, which means that a person with this blood type can donate to anyone. A person with type AB blood is a universal recipient, as long as the Rh factor is compatible.

People with type O-negative blood are considered "universal donors" because their blood doesn't have any antigens or proteins, meaning anyone's body will be able to accept it in an emergency.

While all blood types are needed, type O negative donors are especially important. Because it is the universal blood type and can be transfused to patients of any blood type, type O negative blood ...