May 4, 2009

Green bacteria can harvest light energy

A U.S.-led international team of scientists says it has determined the structure of chlorophyll molecules in green bacteria that harvest light energy.

The researchers said their findings might one day be used to build artificial photosynthetic systems, such as those that convert solar energy to electrical energy.

We found that the orientation of the chlorophyll molecules make green bacteria extremely efficient at harvesting light, said Pennsylvania State University Professor Donald Bryant, one of the team's leaders. Bryant said green bacteria are a group of organisms that generally live in extremely low-light environments, such as in light-deprived regions of hot springs and at depths of about 325 feet in the Black Sea.

The bacteria contain structures called chlorosomes, which contain up to 250,000 chlorophylls.

The ability to capture light energy and rapidly deliver it to where it needs to go is essential to these bacteria, some of which see only a few photons of light per chlorophyll per day, Bryant said.

He said the chlorosomes in green bacteria are the last class of light-harvesting complexes to be characterized structurally by scientists.

The study appears in the Proceedings of the National Academy of Sciences.