Biotechnology

Paths of Least Resistance

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Science  20 Nov 2009:
Vol. 326, Issue 5956, pp. 1043
DOI: 10.1126/science.326.5956.1043-d

Shewanella.

CREDIT: U.S. DEPARTMENT OF ENERGY

Living cultures of bacteria may seem like unlikely candidates to help generate electricity. Yet microbial fuel cells are indeed intriguing complements to other alternative energy schemes, despite the need for improvements in scalability and power-generation efficiency before they can be used in certain environments (e.g., organic-rich marine sediments or wastewater treatment plants). Advancements in efficiency may be achieved by identifying and then optimizing the important components of well-characterized species, or by identifying new bacteria that are inherently more efficient. On the first front, Newton et al. found that despite reducing environmental substrates such as Fe and Mn at a similar rate, two closely related species from the Shewanella genus produce very different current profiles over time. As mutants lacking certain proteins exhibited lower current generation, the mechanism of anode reduction—either through the production of mediator compounds or by direct attachment to the anode surface—emerged as a key efficiency determinant. On the second front, Fedorovich et al. isolated the dominant current-producing species from a mixed culture of bacteria from natural sediments. The new isolate is from a previously underrepresented class of Proteobacteria.

Appl. Environ. Microbiol. 75, 10.1128/AEM.01142-09; 10.1128/AEM.01345-09 (2009).

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