A Longer History of Nannobacteria

How did the controversial subject of nannobacteria get started? In the late 1970’s RLF was looking for another excuse to continue doing field work in Italy, with which he was infatuated. Rome has many great monuments, such as the coliseum, built out of travertine quarried from Tivoli, about 30 km east of Rome. But travertine, though a variety of limestone, was unclassifiable by any of the currently popular systems (Folk, 1959); in fact petrographically it appeared baffling. Hah! Here was a good excuse: why not work up the petrography of these carbonate deposits, formed in lakes fed by sulfurous warm springs? So, in 1979 RLF went to Tivoli to study these rocks with Prof. Henry S. Chafetz (University of Houston sedimentary petrologist) who had worked previously on American travertines. We discovered, entirely by accident, that many features of these rocks had been constructed by sulfur-bacteria; for both of us this was a career-changing discovery because neither of us previously knew or cared anything about bacteria.

Travertines turned out to be fascinating rocks, and in 1985 Victoria Pursell completed a thesis on Yellowstone travertines, formed in very hot water so that aragonite was a major mineral. Pursell came across an Italian reference to hot-spring aragonite travertines at Viterbo, central Italy. Hah Hah! Another excuse to do field work in Italy. In 1988 RLF, accompanied by Paula Noble, began study of Viterbo hot springs. The University of Texas at that time had a cheap SEM that could get up to 10,000X only on good days. In late 1989 the department got a new JEOL SEM that was able to get good resolution at 100,000X. Suddenly a new universe was there for the taking! Not only were abundant "normal"-sized calcified bacteria revealed, but also great numbers of tiny balls in the 0.05-0.25 micron range. After many puzzling months, RLF finally went to the Biology library and found that, yes, dwarfed bacterial cells were known, variously called spores, resting stages, or ultramicrobacteria. Along the way, a friend stopped by to examine the photos and said that these looked like what had been called "nannobacteria" (term coined by R. Y. Morita in 1988).. So Folk adopted that term, analogous to "nannoplankton" or "nannofossils" common terms in geology dating back to the 1800’s.

The first public exhibition of these tiny cells was in Nottingham, September 1990, where RLF lectured on Viterbo carbonates and bacteria as seen by the SEM. During the next couple of years he extended the study from travertines to normal marine limestones, then to sulfur and metallic sulfides, finding bacteria in all these rocks. Something to note, however; the ultramicrobacteria, etc., of Morita and others were terms applied to cells smaller than 0.3 microns, but that were still visible with the light microscope (which cannot reveal objects smaller than about 0.25 microns). The "nannobacteria" seen by SEM in rocks were much smaller, 0.05 to 0.25 microns. This is all the more reason to distinguish them by separate terms. The first public presentation using the word "nannobacteria" in the title was in 1992 where a lecture was delivered showing their presence in many other minerals as well as carbonates. In 1993 we began finding nannobacterial textures on clay minerals and other silica minerals (chert and opal). Corroded metals such as iron, copper, aluminum and lead also are covered with these small balls.

At about the same time, a group of medical researchers in Kuopio, Finland, working with Dr. E. Olavi Kajander, had begun finding "nanobacteria" in mammal blood, including that of humans. They have been publishing extensively on these since 1992, have biogenic particles as small as 0.05 microns, and have retrieved DNA on particles as small as 0.2 microns. The Kuopio group has found them to be involved in the formation of dental plaque and kidney stones, as well as floating in the blood stream.

In 1996 the world was astounded by NASA’s (McKay et al., 1996) claim that they had found nannobacteria similar to these features found on earth, in the Martian meteorite ALH84001. The science of astrobiology was born, but the biological profession immediately rose to the attack!

For more about fieldwork in Italy go here.

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