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What Hungry Microbes Eat Under The Sea

Photoredox catalysis and organocatalysis join forces to connect saturated aldehydes or ketones with aryl cyanides at a spot once deemed inert

by Sarah Everts
April 1, 2013 | A version of this story appeared in Volume 91, Issue 13

The cold, oxygen-free sediment at the bottom of the sea hosts a wealth of microbes. Many bacteria living there survive by metabolizing methane as a carbon source, and researchers had assumed that archaea did the same. But researchers led by geomicro­biologist Bo Barker Jørgensen at Aarhus University, in Denmark, have found evidence for something different: Archaea appear to dine on proteins lurking in the marine sediment (Nature, DOI: 10.1038/nature12033). For their discovery, the team went fishing in the seafloor of a Danish bay. Using core samples, they extracted individual cells from four species of archaea. Sequencing the genome of these archaea they found genes for enzymes that are excreted from cells and can break down proteins, genes for di- and tripeptide transport machinery that delivers dinner back into the cell interior, and genes for enzymes inside the cell that break down amino acids. One of the archaea has enzymes to metabolize d-amino acids, suggesting that the microbe might be getting its proteins from peptidoglycans of bacteria living in the sediment. The finding changes our conception of the marine sedimentary carbon cycle, the researchers note, as it was previously assumed that bacteria are primarily responsible for organic matter recycling in sediments.


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