Cows Aid Quest For Biofuels

By sequencing the DNA of microbes found in the cow foregut, or rumen, a multi-institution team led by researchers at the Department of Energy’s Joint Genome Institute has identified tens of thousands of genes and dozens of enzymes that assist the ruminants in digesting their fibrous diet (Science, DOI: 10.1126/science.1200387). The treasure trove of data is expected to help improve the efficiency and reduce the cost of industrial-scale enzymatic processes that deconstruct cellulosic biomass for conversion into biofuels. Like most microbes, those found in the cow rumen are difficult to cultivate in a lab, thus “metagenomic” studies such as the one led by Matthias Hess, Alexander Sczyrba, and Edward M. Rubin provide an alternative method of discovery and data analysis. The researchers worked with fistulated cows, which allow direct access to the rumen through an implanted tube. They placed switchgrass samples into the rumen through the tube, then later removed the samples and isolated the microbes involved in digestion. The researchers whittled down more than 2 million predicted genes to 27,755 candidate genes that encode for carbohydrate-active enzymes, ultimately identifying and testing 51 enzymes with cellulose-degrading activity. To obtain additional insight, the team used computational puzzle-solving approaches to assemble the genomes of 15 rumen microbes.