Life without oxygen: the energy saving mechanisms of anaerobic gut bacteria.

When faced with limited availability of a certain resource, an effective strategy is to use that resource more efficiently. In the human gut, thousands of species of bacteria compete for limited carbon sources.  However, without oxygen, metabolism can be 10 times less efficient at extracting energy from these carbon sources. We present a study on the energy saving mechanisms of Bacteroides thetaiotaomicron, a representative gut organism which is surprisingly energy efficient for an anaerobe. Through proteomic and metabolomic analysis, we find the molecular mechanisms that underlie this organism's ability to grow efficiently in such a competitive environment. This strategy revolves around the efficient use of pyrophosphate, an ATP analogue that aerobes typically disposed of as waste. Ultimately, use of this molecule comes with the cost of reduced protein synthesis rate, a cost which cells must consider. Given the widespread presence of pyrophosphate-utilizing enzymes in anaerobic genomes, this tradeoff in energy saving is common throughout the anaerobic world.