Microbiology

More A's than B's

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Science  01 Sep 2006:
Vol. 313, Issue 5791, pp. 1203-1205
DOI: 10.1126/science.313.5791.1203d

In contrast to eukaryotes and bacteria, archaea have only recently become the objects of study, and then primarily as hardy denizens of extreme environments, such as hot springs or acid mines. However, as analytical techniques for detecting trace amounts of archaeal components in unpurified samples have been refined and more widely applied, evidence has been accumulating that these species are likely to participate in biogeochemical cycles that affect all spheres of life.

Wuchter et al. and Leininger et al. have looked at the archaea-based oxidation of ammonia in North Sea waters and in northern European soil, respectively. They have measured the amounts of the gene encoding ammonia monooxygenase, the first enzyme in the nitrification pathway, and correlated these data with the presence of Crenarchaeota-specific lipids. Quantitation of ammonia monooxygenase genes in the upper 1000 m of the North Atlantic and across pristine and fertilized soils revealed that the archaeal version was generally several orders of magnitude more abundant than the bacterial enzyme. Incubation of the marine sample and estimates of the rates of Crenarchaea growth and production of nitrite yielded an oxidation flux of about 3 fmol of NH3 per cell per day, which could be extrapolated to a global inorganic carbon fixation rate of 4 × 1013 mol of C per year. — GJC

Proc. Natl. Acad. Sci. U.S.A. 103, 12317 (2006); Nat. 442, 806 (2006).

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