Saturday, May 13, 2006

Undersea bacteria reveal possible path to the origins of life

Methanosarcina acetivorans
Methanosarcina acetivorans, a bacterium first discovered 20 years ago in anoxic mud under kelp beds has a metabolic pathway that may reveal how the first cells produced energy. The bacteria use a common metabolic pathway in an unusual way, to produce acetate (and acetic acid, aka vinegar) rather than methane. In conditions like those hypothesized for the earliest life, areas with high levels of sulfur compounds, the vinegar would be converted to a different form which could have provided an energy source to early life.

The researchers argue that this approach to understanding the earliest life solves major problems with the two dominant theories on early life. Most people try to understand how the earliest life developed the chemical pathways for fixing carbon into useful organic molecules. This system allows energy fixation to evolve first, with the extraction of useful carbon built on the scaffolding of those energy extracting reactions.

The researchers have previously found that the bacterium has genes which hint at the path life took in adapting to an oxygenated environment, and have found that it can digest industrial pollutants.

By tracing molecular evidence, matching it with biochemistry, geochemistry and the hard work being done at the interface of both with biology, these researchers are giving us a peek at how the earliest life might have spent its days. Understanding the full genome of the bacterium was a necessary tool for detecting this molecular pathway, and for determining that it was as ancient as it appears to be. Biology is in its golden age because of the combination of a powerful unifying theory and sophisticated analytical techniques which allow that theory to be applied and tested in diverse settings.

This research doesn't just take us back in time, it also offers us a view of our future. The Methanosarcina bacteria are major producers of greenhouse gases, producing methane in cows' guts, in decaying compost, in oil wells, and sewage pools. Understanding how to control them may help to regulate the release of methane into the atmosphere, and might also offer a way to produce natural gas commercially.