Nanobes are tiny filamental structures first found in some rocks and sediments. Some hypothesize that they are the smallest form of life, 1/10th the size of the smallest known bacteria. No conclusive evidence exists for whether these structures are, or are not, living organisms, and their classification is controversial.
Nanobes were discovered in 1996 (published in American Mineralogist, vol 83., 1998) by Philipa Uwins, University of Queensland, Australia. They were found growing from rock samples (both full-diameter and sidewall cores) of Jurassic and Triassic sandstones, originally retrieved from an unspecified number of oil exploration wells off Australia's west coast. Depths of retrieval were between 3,400 metres (2.1 mi) and 5,100 metres (3.2 mi) below the sea bed. While Uwins et al. present assertions against it, they do not exclude the possibility that the nanobes are from a surface contaminant, not from the rock units cited.
The smallest are just 20 nanometers in diameter. Some researchers believe that these structures are crystal growths, but the staining of these structures with dyes that bind to DNA might indicate that they are living organisms. They are similar to the structures found in ALH84001, a Mars meteorite found in the Antarctic. Recently there has been some interest amongst bio-tech companies in commercial application of nanobes in utilization of plastics.
Nanobes are similar in size to nanobacteria, which are also structures that have been proposed to be extremely small living organisms. However, these two should not be confused. Nanobacteria are supposed to be cellular organisms, while nanobes are hypothesized to be a previously unknown form of life.
A review in Microbes and Environments of the various ultra-small forms of proposed life stated that the main criticism of nanobes is that they appear too small to contain the biochemical machinery needed to sustain life. The review also stated that there is no evidence that nanobes are organisms in themselves and not fragments of larger organisms.