| A Brief History of Nannobacteria Nannobacteria in minerals were born in 1990 when Bob Folk, during high magnification SEM study of hot springs carbonates, discovered tiny 25-200 nm scale spheroidal and ovoid shaped objects in the calcite and aragonite. Because of the general resemblance between these objects and eubacterial Cocci, Bacilli, Streptococci, and Staphylococci, and because of their tendency to occur in chains or clusters, it was initially proposed that the objects were "dwarf forms," about one-tenth the diameter of ordinary of bacteria, "nannobacteria" (sic) (Folk, 1992; 1993a), or their fossilized equivalents, "nanofossils" (McKay et al., 1996). Since then, these nanometer-scale objects have been hypothesized as fossilized microbes in terrestrial carbonates, sulfides, oxides, clays, and other silicates (Folk, 1992, 1993a, 1993b; Pedone and Folk, 1996; Vasconcelos and McKenzie, 1997; Sillitoe et al., 1996; Folk and Lynch, 1997), and in extra-terrestrial rocks, including Martian meteorite ALH84001, and Allende and Murchison carbonaceous meteorites (McKay et al, 1996; Folk and Lynch, 1997, 1998; Folk et al., 1998). Similar nanometer-scale spheroids have been found in mammalian blood and evidence has been presented that they are cytotoxic both in vitro and in vivo (Akerman et al., 1993; Çiftçioglu and Kajander, 1998; Çiftçioglu et al, 1997; Kajander et al., 1997), they may play a role in tissue calcification (Kajander and Çiftçioglu, 1998) and they have been detected in human dental calculus, and arterial plaque. Controversy The genuine existence, and biological nature, of nanometer-scale objects has been severly challenged in both the geological and microbiological communities. The focus of geologic objections to the actuality of nannobacteria and nanofossils is that features of this scale may have many possible origins, e.g. micromineral inclusions or crystallographic edge effects (Bradley et al., 1997). Another major objection is that the nanometer-scale objects are artifacts of conductive heavy-metal coating, but experiments have shown that the gold-coating procedures we use avoid the formation of such artifacts (Peters, 1985; Folk and Lynch, 1997). However, experiments have also shown that nanometer-scale objects that are strikingly similar in appearance to nannobacterial can also be produced inorganically (see Balls of a Different Color). Critical attention from the microbiology community has focused on the small size of the purported nanobacteria, which are often only 1/1000th of the volume of typical bacteria. A cell at the small end of the size range of purported nanobacteria (<50 nm) is thought too small to contain all the nucleic acids and ribosomes necessary for independent life (Nealson, 1997). A workshop was convened by the National Academy of Science in October 1998 to erect a Maginot Line against the nannobacterial heresy. However, a few examples of bacterial cells less than 200 nm in diameter (the common lower size limit defined in microbiology textbooks) have been reported. For example, soil ultramicrobacteria have diameters as small as 80 nm and internal structures in such organisms have been identified by TEM (Bae et al., 1972). Marine ultramicrobacteria have been found (Button et al., 1993), and bacteria are known to greatly reduce their size and cell volume into the size range of purported nanobacteria when severely stressed (Morita, 1988; Cusack et al., 1992). Furthermore, the Finnish group has illustrated cells with cell walls with diameters as small as 50 nm. In any case, nannobacteria are larger than most viruses (10-20 nm) which are certainly some form of biological particle, even if they are not "life" as we know it. Implications If these tiny structures are truly living organisms, then their significance to terrestrial processes is far-reaching and profound. Nannobacteria may be mediating many processes currently assumed to be controlled by inorganic chemical reactions, such as low-temperature precipitation of dolomite, oxidation of iron, and the formation of clay minerals on the Earth's surface (Folk, 1992; 1993); processes which have an economic effect on many industries including petroleum exploitation and environmental mediation. Nannobacteria may also be controlling processes within organisms such as formation of shells, bones, teeth, calculus, and arterial plaque. They have been reported from bovine, rabbit and human blood and they may be associated with human disease. It has been suggested that nannobacteria might play a role in a class of diseases associated with mineralized amyloid deposits in human tissue (including inflammatory bowel disease, kuru, Kreutzfeld-Jacob’s, Alzheimer’s, and Crohn’s disease) (M. Taylor, personal communication). The discovery of nannobacterial textures in the Martian Meteorite ALH84001 (McKay et al., 1996), the Allende meteorite (Folk, 1997; Folk and Lynch, 1997), and the Murchison meteorite (Folk et al., 1998) have raised the possibility that nanofossils are harbingers of the existence of extraterrestrial life. Iron-rich clay minerals (such as nontronite, saponite, and Fe-montmorillonite) identified in altered volcanic rocks in hot springs contain nanostructures identical to those seen in the Martian meteorite (Lynch and Folk, 1996). These clays are known to form in low- or zero-oxygen atmosphere environments such as Precambrian Earth and ancient Mars, and the presence of Fe-rich clays on Mars has also been suggested by IR spectroscopic analyses and by simulation of the Viking Limited Release experiment (Banin and Margulies, 1983; Banin, 1986; Reynolds, 1986). In addition, the clays identified in altered terrestrial volcanic rocks are able to absorb and polymerize amino acids into long chain polypeptides, molecules that are considered basic building-blocks of life (Burton and Newman, 1971; Paecht-Horowitz and Katchalsky, 1973; Lahav et al., 1978; Odom et al., 1979; Lawless et al., 1985). The close association between these catalytic clays and potentially the most primitive form of life (e.g. nanobacteria) may provide insight into the very origin of life on Earth. So just what are these things?? STAY TUNED!!!!!
References Cited
Go to "A Longer, More Personal History of Nannobacteria" by Bob Folk
Go to the Photo Gallery
Acknowledgements This research has been supported by National Science Foundation grant EAR-980301 (to Kirkland), Texas Higher Education Coordinating Board Advanced Research Program Grants #160 (to Kirkland and Folk) and #005 (to Folk at the Bureau of Economic Geology (with help from R. P. Major, now Chair, Department of Geology and Geological Engineering, University of Mississippi)), the Geology Foundation at the University of Texas at Austin, and the DuPont Foundation. Mike Rahnis and Carey Suehs contributed greatly to certain parts of this project, and Dennis Trombatore remains a friend of nannobacteria. Most of the photographs shown were taken by R. L. Folk or F. L. Lynch. This purported website is a Schiavo Leo production (claynac@ra.msstate.edu). 
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