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DOE Grand Challenge Project Completes Sequencing of Cyanobacterium

A Department of Energy Grand Challenge project led by Washington University in St. Louis has resulted in the rapid sequencing and annotation of a cyanobacterium that could yield clues to how environmental conditions influence key carbon fixation processes at the gene-mRNA-protein levels in an organism.

Learning the intricacies of these organisms could lead to breakthroughs in the understanding of both biological carbon sequestration and hydrogen production, according to Himadri Pakrasi of Washington University, the project leader, speaking at the annual meeting of the American Association for the Advancement of Science in St. Louis.

The project is one of two Grand Challenge Projects recently funded by the W.R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a National User facility managed by the Pacific Northwest National Laboratory for the Department of Energy (DOE).

The project team is using a systems approach to understand the network of genes and proteins that govern the structure and function of membranes and their components responsible for photosynthesis and nitrogen fixation in two species of unicellular cyanobacteria, specifically Cyanothece and Synechocystis.

According to Pakrasi, the team has made significant progress in five key areas. Through Washington University’s Genome Sequencing Center, researchers have sequenced and annotated 99% of the Cyanothece 51142 genome, designed a microarray for global transcriptional analysis of the organism and have completed half of a proteomic map—some 2,400 proteins.

The researchers have designed a novel photobioreactor for mass balance analysis of Cyanothece cells during circadian cycles, and used X-ray crystallography to determine the atomic structures for five proteins involved in sequestering such key nutrients as iron, nitrate and bicarbonate.

Cyanobacteria have played an influential role in the evolution of the terrestrial environment. They precede chloroplasts in evolution and are largely responsible for today’s oxygen-rich environment. They make significant contributions to harvesting solar energy, sequestering carbon, bio-assimilating metals and the production of hydrogen in marine and freshwater ecosystems.

Cyanobacteria also are model microorganisms for studying the fixation of carbon dioxide and nitrogen at the biomolecular level. Learning the intricacies of these organisms could lead to breakthroughs in the understanding of both biological carbon sequestration and hydrogen production.

—Dr. Pakrasi

A systems approach integrates all available temporal information into a predictive, dynamic model to understand the function of a cell and the cellular membranes. Because Cyanobacteria make significant contributions to harvesting solar energy, planetary carbon sequestration, metal acquisition, and hydrogen production in marine and freshwater ecosystems, the genetics and biochemistry of these organisms are particularly suitable for such an approach.

Cyanothece, a one-celled marine cyanobacterium, has the ability to produce oxygen and assimilate carbon through photosynthesis during the day while fixing nitrogen through the night, all within the same cell.

Pakrasi and his collaborators are growing Cyanothece cells in photobioreactors, testing cells every hour to try to understand the cycles at different times of the day. With the combined diverse expertise of 16 different laboratories, the Grand Challenge scientists and engineers are examining numerous biological aspects of the organism.



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