|MadSci Network: Microbiology|
Nanobacteria definitely exist and they have been found on earth in such
places as human and cow blood. Researchers E. Olavi Kajander and his
colleagues from the University of Kuopio in Finland have even been able
to culture them in bovine (cow) serum. These researchers also believe
that they grow in urine and may be the cause of most kidney stones.
Nanobacteria are thought to be the smallest cell-walled bacteria.
Depending on the environment they live in they can vary dramatically in
size. Under unfavorable conditions they form very large multi-cellular
units, but they can release much smaller particles, some of which are
only 50 nm in size (smaller than many viruses) when the conditions are
not so favorable. Although metabolic rates of nanobacteria are very slow,
they can produce carbonate apatite on their cell envelope mineralizing
rapidly most of the available calcium and phosphate. This is why the
researchers believe that they may be the cause of most kidney
Nanobacteria belong to, or may be ancestors of, the alpha-2 subgroup of
Proteobacteria. They may still partially rely on primordial life-
strategies, in which minerals and metal atoms associated with membranes
played catalytic and structural roles reducing the number of enzymes and
structural proteins needed for life. In other words, they use the
external environment to do a lot of the work that most bacteria perform
inside their own cells. This allows them to be much smaller than most
bacteria since their cells do not have to house all of the normal
machinery of life. They simply don't need all that extra space. This
simplistic life strategy may also explain the ability of this life-form
to survive in extreme environmental conditions and their very slow growth
rates (10000 times slower than E. coli!).
However, the name nanobacteria is highly controversial as you may have
discovered. The controversial nature of the name nanobacteria swirls
around its previous use with the slight difference in spelling
nannobacteriaby Robert L. Folk, a geologist at the University of Texas
at Austin. For almost two decades, Folk has riled microbiologists by
claiming that bumps and knobs that he sees in electron microscope
pictures of soils and rocks represent bacteria with diameters as small as
According to Folk, such nannobacteria are widespread and plentiful, and
by precipitating various minerals, they may have had a major impact on
geology. His speculations gained greater notoriety in 1996 with the
discussion of possible evidence of extraterrestrial life in a meteorite
from Mars. One group of scientists suggested that the so-called
microfossils detected in that meteorite resemble Folk's
Many microbiologists, however, argue that Folk offers no compelling
evidence that his bumps and knobs are alive. These scientists remain
intensely skeptical that bacteria that small can exist. "The Folk stuff
really stretches the theoretical limits. . . . It doesn't just stretch
them, it denies them," says Kenneth H. Nealson, a microbiologist at the
NASA's Jet Propulsion Laboratory in Pasadena, Calif.
While bacteria generally have diameters of a micrometer (1000 nm) or
more, biologists have for many years recognized the existence of tinier
bacteria, whose diameters range from 50 to 200 nm. Below such sizes,
Nealson and others claim, there's simply not enough room to contain the
machinery of life as we know it.
Even a bacterium 50 nm in diameterthe smallest that Kajander describes
would be jam-packed, assuming its cell walls were about 10 nm thick and
the microbe contained DNA and even one protein-making ribosome, which is
25 nm in diameter. "At 50 nm, one could imagine that things could stay
alive. When you get much smaller than that, it's really hard to imagine,"
Here is a link to a site that you might help you better understand the
current research surrounding nanobacteria:
Travis, John. Science News, Vol. 154, No. 5, August 1, 1998, p. 75.
Kajander, E.O., and N. Çiftçioglu. 1998. Nanobacteria: An alternative mechanism for pathogenic intra- and extracellular calcification and stone formation. Proceedings of the National Academy of Sciences 95(July 7):8274.
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