Mayo Clinic researchers have found evidence for the existence of controversial “nanobacteria” — a possible new life form. The research suggested that the organisms are self-replicating in culture and could be identified with an antibody and DNA stain.

Some scientists say nanobacteria are responsible for a wide range of diseases, including calcification of the arteries.

Others say they are simply too small (50 to 500 nm) to be living creatures, since to contain the DNA and proteins needed to function, a cell must be at least 140 nanometres across.