Expanding Archaeal Diet

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Science  26 Nov 2010:
Vol. 330, Issue 6008, pp. 1156
DOI: 10.1126/science.330.6008.1156-c

Archaeal methanogens transform carbon dioxide into methane under an extraordinary range of conditions, unfazed by surrounding acids, bases, salts, or extremes of temperature. However, they are for the most part quite choosy about their substrate. Lessner et al. now show that by introducing an esterase enzyme (MekB) from an aerobic bacterium into the metabolic pathway of one such methanogen, they can extend the organism's diet to encompass methyl esters of acetate and propionate. On incorporation of a plasmid encoding MekB, Methanosarcena acetivorans proved capable of growing and emitting methane with either ester acting as the sole carbon source. Methanol appeared to be the portion of the ester most readily reduced; acetate was transformed more slowly, whereas propionate simply accumulated as a by-product. The success of merging pathways from bacterial and archaeal domains, coupled with the effectiveness of the resulting engineered organisms in consuming common esters, bodes well for broader applications in processing biomass and organic waste products to form energy-dense natural gas.

mBio 1, e-00243-10 (2010).

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