Nanobacteria are a putative novel life form first identified in the 1990s and implicated in the origin of life and in a variety of diseases. Now it seems that nanobacteria may simply be calcium carbonate nanoparticles, according to research by Jan Martel of Chang Gung University, in Taiwan, and John Ding-E Young of Rockefeller University (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.0711744105). Martel and Young used published methods to "culture" nanobacteria from human blood and compared the resulting nanospheres to calcium compounds likely to precipitate in biological fluids. They found that calcium carbonate nanoparticles (shown) prepared in cell culture media from (NH4)2CO3 and CaCl2 closely resemble previously reported isolated nanobacteria. Specifically, the CaCO3 nanoparticles appear to have an amorphous layer at the surface that looks like a membrane, and two adjacent particles seem to be undergoing cell division. The researchers also found that purported nanobacteria-specific antibodies, which are commercially available, may bind to serum albumin and form an insoluble matrix with CaCO3. Before now, CaCO3 particles had only been identified in the inner ear, so finding them in other tissues such as blood may have implications for disease pathology.