“Great fleas have little fleas upon their backs to bite ’em,
And little fleas have lesser fleas, and so ad infinitum.”
So declared Augustus de Morgan, developing a theme by Jonathan Swift in response to naturalists’ ability to find ever-tinier creatures with their new microscopes. A new class of microbe now threatens to upset the rules about how small a living thing can be, as well as splitting the medical community on whether they even exist. The microbes in question are known to their supporters as nanobacteria. Normal bacteria are typically between 0.3 and 5 micrometres (microns or µm) in length; the new discoveries can be as small as 0.02µm. According to proponents, they are dangerous, and are possibly connected to human diseases from Alzheimer’s to arthritis to cancer. These nanobacteria seem to have the Medusa touch, turning flesh into stone.
In 1998 Olavi Kajander and Neva Çiftçioglu at the University of Kuopio in Finland isolated the nanobacteria from human blood, urine and saliva. They describe them as being based on RNA rather than DNA. RNA contains the pyrimidine base uracil, rather than thymine as in DNA; it is generally single-stranded and does not form such long chains as the more stable double-stranded helix of DNA, and so carries less information. Kajander and Çiftçioglu believed nanobacteria normally lived in deposits of apatite, a calcium-based mineral found in bones and teeth, surrounding themselves with calcium phosphate. In other parts of the body they form a film that can make potentially harmful stony microcalcifications, including a type associated with ovarian cancer. This seemed like a medical breakthrough and suggested a possible pathway for dealing with medical conditions associated with the nanobacteria. Treatments were released based on the drug EDTA, which promotes the transfer of calcium back into bone.
Nanobacteria were also good news for NASA. In 1996, they had claimed that the Martian meteorite ALH84001 contained evidence of life in the form of tiny fossil remains. The problem was that the “fossils” were much smaller than any known bacteria, being 0.02–0.1µm across. The discovery of nanobacteria made it far more credible that these were genuine fossils and geological pseudofossils. However, there was considerable resistance in the medical community to Kajander and Çiftçioglu’s claims. It had long been accepted that calcification was caused by purely chemical processes, even though these were not understood. It was also argued that nanobacteria would be too small to contain the basic mechanisms necessary for life.
Others set out to reproduce the work, and the results were not encouraging. Although the original researchers believed they had found traces of RNA associated with the nanobacteria, others found that these were actually from a bacterium that often contaminates the analysis process. Nobody has successfully isolated nanobacteria to the extent that they can be used to infect a sample, let alone be cultured and extracted. This is one of the standard requirements for new bacteria to be accepted (known as Koch’s postulates). Until and unless this is met, nanobacteria will remain in a twilight world of half-acceptance.
However, nanobacteria have already spawned a small industry. Pasquale Urbano of the University of Florence’s Institute of Microbiology suggests that there is “an aggressive risk-mongering and disease-mongering campaign” and that research in this area suffers from nanobacteria’s ambiguous state. Rejected papers collect in a pool of “grey literature” familiar to followers of fringe science. Believers say that such papers are only rejected because of the establishment’s closed-minded attitude, while sceptics simply view them as bad science.
Another blow was struck against nanobacteria in 2007 by researchers from Chang Gung University in Taiwan and the Rockefeller University in New York. They concluded that non-living calcium carbonate particles were “remarkably similar to purported nanobacteria” in terms of their size, shape and tendency to reproduce and form “colonies”. Finally, according to the National Academy of Sciences’ Workshop on Size Limits of Very Small Microorganisms, living things must be at least 0.2µm across to accommodate the DNA necessary for reproduction. This would seem to finally put an end to any possibility of nanobacteria.
However, forteans know better than to accept any such assertion as an unbreakable law. And sure enough, there are signs that nanobacteria may exist. This time the evidence has not come from the human body but from geology. Jill Banfield of the University of California, Berkeley, has discovered a new type of bacterium belonging to the phylum Achæa in acidic mine sludge. These are right down at the 0.2µm size limit. And nanoorganisms discovered in Australian sandstone appear to be even smaller – as little as 0.02µm. Further, they gave positive results to some DNA tests, a strong indication that they are genuine living things. However, further work will be needed before the Australian nanobes can be confirmed.
The most important scientific battleground is over the nanobacteria (or “calcifying nanoparticles”, depending on whose side you take) that have been found in humans. For the medical profession, the important question is not over whether they are living things, but whether they really do cause certain diseases and how they can best be treated.
There is a precedent here with Prions, which cause BSE (“mad cow disease”) and other conditions. Prions are fragments of protein capable of reproducing inside a host. They do not fit the criteria for life, but they are dangerous agents of infection. They are also tiny, just 0.01µm across.
Nanobacteria may not be life as we know it. But they might be life as we do not know it.
For a report on "nanobes”, see FT123:6; see also “The Truth About Nanobacteria”, Scientific American, Dec 2009.