A team of researchers headed by biologists at Washington University in St. Louis has sequenced the genome of a unique bacterium that manages two disparate operations photosynthesis and nitrogen fixation in one little cell during two distinct cycles daily.
Himadri B. Pakrasi, Ph.D., George William and Irene Koechig Professor in Arts & Sciences, spearheaded the drive to sequence the genome of Cyanothece sp. ATCC 51142 to understand the workings of this species that has the ability to produce ethanol and hydrogen, and thus some day become an inexpensive renewable energy source.
Cyanobacteria are the only known bacteria to have a circadian clock. By day, Cyanothece cells increase gene expression for photosynthesis and sugar production; at night, they moonlight, ramping up gene expression that governs energy metabolism, nitrogen fixation, and respiration.
Pakrasi and his collaborators found the presence of a rare linear chromosome in the organism's genome, a first in cyanobacteria. Further examination revealed the chromosome to be 430 kilobases long and containing a cluster of nine genes that code for enzymes involved in pyruvate metabolism, which is the basis that allows Cyanothece 51142 to produce lactate, and other important compounds.
Cyanothece 51142 has one large circular chromosome, the linear chromosome and four small plasmids.
"This is the first time anything like this has been found in photosynthetic bacteria. It's extremely rare for bacteria to have a linear chromosome," said Pakrasi. "Nearly 100 percent of them do not. Now, we have the genome of this organism, which gives us a complete picture of everything that can possibly happen in this cell. The way the cell prospers, multiplies and dies is all decided in the genome.
"This is the benchmark, the prototype, for these cyanobacterial species. Now, we can go back to this complete picture and compare its brother
|Contact: Gayle Geren|
Washington University in St. Louis