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No. 110: Mar-Apr 1997

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Nannobacteria: life on a different scale

Who ever heard of nannobacteria until those tiny, worm-like objects were photographed inside that putative Martian meteorite ALH 84001? It turns out that these very tiny cells (only 0.1 - 0.4 micrometers in diameter) are everywhere on earth, but it seems that virtually no one knows about them. The furor over ALH 84001 has underscored professional and public ignorance of nannobacteria. Some scientists have asserted that bacteria could never be as small as those "objects" seen in the greatly magnified photos of ALH 84001. This claim led R.L. Folk to fire off a letter to Science that began with these two sentences:

"Enough! As one of the discoverers of mineralized nannobacteria on Earth*, I must come to their defense. They are so abundant in samples I have studied that I believe they may make up most of the Earth's biomass."

Folk reports that nannobacteria are found just about everywhere: hot-spring waters, decaying leaves, even blood. Nannobacteria are key players in the earth's surface chemistry, precipitating a host of minerals and acting symbiotically to precipitate organic hard parts.

(Folk, Robert; "In Defense of Nannobacteria," Science, 274:1288, 1996.)

Comment. Ignorance of nannobacteria is not surprising. One needs a scanning electron microscope to see them.

* See: Folk, R.L.; Journal of Sedimen tary Petrology, 63:990, 1993.

From Science Frontiers #110, MAR-APR 1997. � 1997-2000 William R. Corliss