Nature Biotechnology pp 1275 - 1281

Scientists in Korea have sequenced the genome of one of the main organisms contributing to the microflora of a cow's rumen. As described in the October issue of Nature Biotechnology, Lee and colleagues have assembled the 2,314,078 base pair sequence of Mannheimia succiniciproducens. This bacterium loves the oxygen-depleted, CO₂-rich environment of the rumen, the first chamber of the cow's complex stomach designed to degrade hard-to-digest grasses. In addition to determining the genetic makeup of M. succiniciproducens, the authors also reconstructed the main metabolic pathways of this organism that are responsible for its adaptation to surviving in the rumen.

Knowledge of the genome of this bacterium and the comprehensive metabolic picture derived from it will help researchers accelerate the development of applications in which the high CO₂ uptake rates and organic-acid production yields of M. succiniciproducens are exploited toward the manufacture of biodegradable polymers, resins and other chemical compounds.

Nature Biotechnology pp 1282 - 1289

Cells derived from human embryonic stem (ES) cells can impart a new rhythm to pig hearts, according to a report in the October issue of Nature Biotechnology. The pacemaker activity of the transplanted human cells shows that they integrate functionally in the recipient pig hearts and underscores the potential of human ES cells for cardiac repair.

Before human ES cells can be applied in regenerative medicine, scientists must determine whether these cells (or their progeny) can heal injured tissues in animals. Lior Gepstein and colleagues generated heart cells from human ES cells in a culture dish and transplanted them into the hearts of pigs. The pigs had an abnormally slow heart rate that was induced surgically. The transplanted human heart cells partially corrected the abnormality in the pig hearts, like a biological version of an electronic pacemaker. Ultimately, the authors suggest such cell therapies may be used as an adjunct to conventional mechanical pacemakers.