Image: Ed DeLong 2000 MBARI
Picoplankton (right) aren't easy to study. These bacteria--measuring at most two microns wide--float aimlessly in the oceans and are not readily grown in culture. So with good reason, biologists haven't been able to figure out how these organisms fit into the marine ecosystem. But that puzzle just got a lot easier: scientists from the Monterey Bay Aquarium Research Institute have developed a method for dissecting the genome of collected specimens, and in today's issue of Science, they describe an interesting find: picoplankton appear to use an entirely new photopigment to harness light energy.
Lead researcher Ed DeLong and postdoctoral associate Oded Bj isolated large genome fragments from the picoplankton and, with colleagues at Molecular Dynamics, produced raw gene sequences, which were then assembled and analyzed. What they found was a new pigment never before seen in bacterial species that in fact resembled rhodopsins--light-absorbing chemicals associated with vision in the animal kingdom.
Using recombinant DNA technology, DeLong and Bj expressed the rhodopsin-like gene they uncovered and tested its function. Sure enough, the photopigment moved ions across cell membranes when exposed to light, showing that it can convert absorbed light into energy. The implications, they say, are many. For one thing, it suggests that rhodopsin-like pigments may be more prevalent than previously thought. And on an entirely different note, such pigments from tiny creatures may prove well suited to certain nanotechnology applications, like light-actuated molecular switches.