Nanobacterium

Nanobacterium (NAH-no-bak-TEER-ee-əm, pl. nanobacteria NAH-no-bak-TEER-ee-uh) is the unit or member name of a proposed class of living organisms, specifically cell-walled microorganisms with a size much smaller than the generally accepted lower limit for life (about 200 nanometres for bacteria). Originally based on observed nano-scale structures in geological formations (including one meteorite), the status of nanobacteria has been controversial, with some researchers suggesting they are a new class of living organism capable of incorporating radiolabeled uridine, and others attributing to them a simpler, abiotic nature. One skeptic dubbed them "the cold fusion of microbiology", in reference to a notorious episode of supposed erroneous science. The term "calcifying nanoparticles" (CNPs) has also been used as a conservative name regarding their possible status as a life form.

Research tends to agree that these structures exist, and appear to replicate in some way. However, the idea that they are living entities has now largely been discarded, and the particles are instead believed to be nonliving crystallizations of minerals and organic molecules. In medicine, they have been implicated in the formation of both kidney stones and arterial plaque.