14 DAY TRIAL // We normally associate bacteria with harmful germs, provoking some of the most terrible diseases, like plague or tuberculosis. Others are associated with fermenting processes.
Now, a mixed team of Spanish and Swedish researchers at the University of Kalmar and Gothenburg, Sweden, have discovered a unique light-capturing pigment in marine bacteria. "It was long thought that algae were the only organisms in the seas that could use sunlight to grow," said Jarone Pinhassi, a researcher in Marine Microbiology at Kalmar University College.
Marine microscopic algae carry on photosynthesis using chlorophyll and many other types of pigments, in a way similar to terrestrial plants. In 2000, American researchers found for the first time that many marine bacteria carry a gene for an unknown type of light-sensitive pigment: proteorhodopsin. Proteorhodopsin is similar to rhodopsin, the retina pigment that enables us to detect colors.
Scientists supposed that the new pigment must have been used for photosynthesis. But only when the mixed team collected 20 species of marine bacteria from different ocean areas and mapped their genomes, did they actually detect the pigment proteorhodopsin.
Lab experiments clearly proved that the pigment is used by the bacteria to get energy from sunlight. As one liter of natural sea water contains roughly a billion bacteria, the new discovery is a breakthrough in understanding how marine life makes use of sun energy.
From this totally new perspective, the amount of organic substance produced by photosynthetic bacteria must be of great importance to the carbon cycle, and they play a huge role in marine carbon dioxide and nutrition cycles. "Bacteria in the surface water of the world's oceans swim in a sea of light," said Pinhassi.
"And it is shouldn't be too surprising that evolution has favored microorganisms that can use this rich source of energy. This type of protein may also play a role in commercial and environmental perspectives, for the development of artificial photosynthesis for the environmentally friendly production of energy."