Nanobacteria, also known as nannobacteria, are microbes around 25-200 nanometers in size, about 10 times smaller than what is generally considered extremely small bacteria. Nanobacteria are controversial because claims of their existence have only emerged quite recently -- 1990 -- and they are smaller than what is generally considered the lower size limit for a living cell (200 nm). They have alternatively been described as inanimate crystal growths and the most abundant life form on Earth.
The first nanobacteria were discovered in minerals by Bob Folk, who, in a high magnification SEM study of hot springs carbonates, found miniscule 25-200 nm scale spheroidal and oval shaped objects in calcite and aragonite. Because they looked similar in shape to larger bacteria, but much smaller, Folk called them nanobacteria. Since then, there have been claims of findings in a variety of minerals, human and animal blood, and even on the Martian meteorite ALH84001, discovered in 1996 in Antarctica.
Although the existence of nanobacteria has been challenged by both the geological and microbiological communities, many established researchers have published papers on nanobacteria and their alleged effects. One of these effects is supposedly the calcification of blood in our arteries. A fossil of a nanobacterium as been called a nanofossil.
Studies of nanobacteria have been challenging. Because they are so small, it has been difficult to extract genetic material from these entities, meaning that there is still no conclusive proof that they are life forms. It has also been stated that so-called nanobacteria resemble the inanimate structures known to form when calcium and phosphate salts are combined with organic material.
In 1998, Finnish scientists reported isolating RNA from a sample of nanobacteria, but this study was shown to be faulty when the National Institute of Health found that the RNA was derived from a microbe known to contaminate lab equipment. Complicating matters further, it has been claimed that not all the Finnish findings were invalidated, leaving room open for further research and testing. Also in 1998, nanobacteria were accused of contributing to certain diseases when they were observed creating shells of calcium phosphate around themselves.
Living organism or inorganic crystal growths? The true answer is not yet clear. Whatever they are, they're pretty darn small.
Michael is a longtime WiseGEEK contributor who specializes in topics relating to paleontology, physics, biology, astronomy, chemistry, and futurism. In addition to being an avid blogger, Michael is particularly passionate about stem cell research, regenerative medicine, and life extension therapies. He has also worked for the Methuselah Foundation, the Singularity Institute for Artificial Intelligence, and the Lifeboat Foundation.