Two New Prochlorococcus Clades from Iron-Depleted Oceans
Prochlorococcus is one of the most abundant marine photosynthetic microbes and one of the main producers of “food” in the world’s oligotrophic (nutrient poor) oceans. DOE funded research led by the J. Craig Venter Institute has characterized two new distinct clades (branches on the tree of life) of Prochlorococcus. Both clades dominate the eastern equatorial pacific and tropical Indian oceans, known for their high temperatures and low nutrient and iron availability. Using both a phylogenetic and genomic analyses, the two clades were found to be distinct from each other and from other known lineages adapted to high-light environments, and to lack certain iron-reducing proteins which aids them in adapting to the low iron availability. These findings explain why these organisms do not respond to ocean iron-fertilization experiments and shed the light on how phytoplankton adapt to variations in nutrient availability in the oceans. This new characterization of Prochlorococcus and its role in the energy and nutrient cycling in the oceans’ ecosystems will greatly enhance our understanding of both the marine diversity and the biogeochemical cycle. The research has just been published in the Proceedings of the National Academy of Sciences (PNAS) Early Edition.
Douglas B. Rusch, Adam C. Martiny, Christopher L. Dupont, Aaron L. Halpern, and J. Craig Venter “Characterization of Prochlorococcus clades from iron-depleted oceanic regions” PNAS published ahead of print August 23, 2010, doi:10.1073/pnas.1009513107.