Once touted as the world’s smallest living organisms, and even an entirely new form of life, “nanobacteria” are actually nothing more than sub-microscopic balls of minerals and proteins, independent teams of scientists in Taiwan and France report.

However, nanobacteria have been linked to kidney stone and gallstone formation, polycystic kidney diseases, rheumatoid arthritis, some cancers, co-infection with HIV, Alzheimer’s disease and chronic prostatitis. They have also been implicated in hardening of the arteries and aging.

Didier Raoult, a microbiologist at the National Center for Scientific Research in Marseille, France, theorizes that they may function like prions, proteins that cause mad cow disease.