Cyanobacteria, found in just about every ecosystem on Earth, are one of the few bacteria that can create their own energy through photosynthesis and "fix" carbon from carbon dioxide molecules and convert it into fuel inside of miniscule compartments called carboxysomes. Using a pioneering visualization method, researchers from the University of California, Berkeley and the Department of Energy Joint Genome Institute (DOE JGI) made what are, in effect, movies of this complex and vital cellular machinery being assembled inside living cells. They observed that bacteria build these internal compartments in a way never seen in plant, animal and other eukaryotic cells.
"The carboxysome, unlike eukaryotic organelles, assembles from the inside out," said senior author Cheryl Kerfeld, formerly of the DOE JGI, now at Michigan State University and UC Berkeley. The findings, published November 21, 2013 in the journal Cell, will illuminate bacterial physiology and may also influence nanotechnology development.
Although cyanobacteria are often called blue-green algae, that name is a misnomer since algae have complex membrane-bound compartments called organelles -- including chloroplasts -- which carry out photosynthesis, while cyanobacteria, like all other bacteria, lack membrane-bound organelles. Much of their cellular machinery including their DNA floats in the cell's cytoplasm unconstrained by membranes. However, they do have rudimentary microcompartments where some specialized tasks happen.
Looking a lot like the multi-faceted envelopes of viruses, carboxysomes are icosahedral, having about 20 triangle-shaped sides or facets. They contain copious amounts of Ribulose 1,5 Biphosphate Carboxylase Oxygenase (commonly called RuBisCo), an extremely abundant but slow enzyme required to fix carbon, inside their protein shells. The microcompartment also
|Contact: David Gilbert|
DOE/Joint Genome Institute