Human Genome Project Information Genomics:GTL DOE Microbial Genomics home

Image Gallery DOE Microbial Genome Program Report

Designed for Success: DNA Analyses Reveal Details
 

Prochlorococcus marinus

Rubisco

The microscopic marine Prochlorococcus may be the most abundant photosynthetic organism on Earth. Analyses of DNA sequence data now offer some clues as to how the genomic structures of these organisms contribute to their success.

Prochlorococcus marinus MED4 uses the enzyme Rubisco to help convert or "fix" carbon dioxide to complex sugars in carrying out photosynthesis. Oxygen, a byproduct of photosynthesis, competes for Rubisco and could potentially interfere with this process. The organization of Rubisco and other proteins into tiny structures called "carboxysomes" (three dark-colored bodies in photo), however, promote efficient sequestering of carbon dioxide and help promote its fixation to the complex sugars used as chemical energy.

Analyses indicate that the genes encoding Rubisco [cbbL and cbbS above the green line in the screen shot from the Genome Channel] are organized into a complex in the same genomic region that also encodes components of the carboxysome shell proteins (csp). This genetic organization can ensure that the required amounts of each protein are produced at the proper time.

Researchers use multiple systems for identifying genes in microbial DNA; the systems perform well in combination to generate a consensus gene model. The screen shot depicts the result of using three gene-finder programs on P. Marinus DNA sequences: Glimmer (pink line), Critica (orange line), and Generation (green line). Conceptual translation of these gene models are used to search for similarities to other gene sequences in public databases and to determine their relationships to particular protein families. Researchers use these results to construct metabolic frameworks and assign particular functional roles to genomic sequences.

[Genome Channel draft contig view and annotation by Frank Larimer (Oak Ridge National Laboratory); original DNA sequence provided by Jane Lamerdin (Joint Genome Institute and Lawrence Livermore National Laboratory); electron photomicrograph of Prochlorococcus (isolate MIT 9313) courtesy of Sallie Chisholm (Massachusetts Institute of Technology)]