ScienceDaily (Dec. 24, 2004) — Arlington, Va. -- Scientists have sequenced the genome of the microorganism Silicibacter pomeroyi, a member of an abundant group of marine bacteria known to impact the Earth’s ecosystem by releasing and consuming atmospheric gases. This genetic blueprint provides insight into the biochemical pathways the bacterium uses to regulate its release of sulfur and carbon monoxide. Atmospheric sulfur serves as a catalyst for cloud formation, in turn, directly affecting the planet’s temperature and energy regulation, while carbon monoxide is a greenhouse gas.

The interdisciplinary research team, led by Mary Ann Moran at the University of Georgia, includes collaborators at The Institute for Genomic Research (TIGR) and six universities. Their work appears in the December 16 issue of Nature.

While everyone is aware that bacteria can cause disease, it’s less obvious that these microorganisms play an important part in the global ecosystem. “Having the genome of S. pomeroyi completely sequenced provides an invaluable tool to understand how an ocean bacterium functions and how it affects the Earth’s atmosphere,” says Moran. The knowledge gained from continued study of S. pomeroyi and its genome will be used in the study of related organisms that likewise mediate carbon and sulfur cycling in the ocean. Moran continued, “Admittedly, this is not the only bacterium that influences gas exchange between the ocean and atmosphere, but once we understand how S. pomeroyi functions, we can apply the knowledge to other related marine bacteria.”

The genome, similar in size to that of the more familiar Escherichia coli, is composed of a 4.1 million base pair main chromosome and a 491,000 base pair extra-chromosomal piece of DNA. Early investigation of the genome found 4,283 regions in the genome that are predicted to code for the synthesis of proteins and other cellular machinery.

This work is funded through the Microbial Genome Sequencing Program, a collaborative, interagency effort between NSF and the United States Department of Agriculture (USDA). The program supports research projects that sequence genomes from a broad range of microorganisms in order to provide a foundation for understanding how microorganisms function and live, and how they evolve and interact with their environments and other organisms.

This diagram illustrates how Silicibacter pomeroyi influences climate. One of the compounds that S. pomeroyi releases is dimethyl sulfide gas, which photoxidizes in sunlight to form microscopic sulfate particles. The particles serve as sites for water to condense into cloud droplets. The concentration of these droplets impacts how clouds reflect and absorb radiation, which affects climate. (Credit: National Science Foundation)

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