14 DAY TRIAL // The process of photosynthesis is perhaps the most important one on Earth, as it is the source of our oxygen, and also a huge storage facility for atmospheric carbon dioxide, of which we pump copious amounts in the atmosphere. But one of the bases for this process is the vegetation's ability to capture and convert light into energy, a phenomenon that provides sufficient power for all other aspects of photosynthesis. Now, an international team of experts believe they may have found the key elements that make plants able to capture light, namely their highly effective optical processors, called chlorophylls.
The team, made up of researchers from the Penn State University, the Leiden Institute of Chemistry and the Groningen Biomolecular Sciences and Biotechnology Institute in the Netherlands, and the Max Planck Institute in Germany, and funded by the United States Department of Energy (DOE), believe that the new find could pave the way for brand new artificial photosynthetic systems one day, such as those that are currently employed for changing solar light into electricity in photovoltaic panels.
“We found that the orientation of the chlorophyll molecules make green bacteria extremely efficient at harvesting light. The ability to capture light energy and rapidly deliver it to where it needs to go is essential to these bacteria, some of which see only a few photons of light per chlorophyll per day,” team leader Donald Bryant, who is the Ernest C. Pollard professor of Biotechnology at Penn State, explains. He adds that the most fruitful research was conducted on green bacteria, which can be found in thermal springs and at depths of up to 100 meters in the Black Sea, off Eastern Europe.
This type of bacteria comprises structures called chlorosomes, which contain up to 250,000 chlorophylls each. This makes for a highly efficient optical sensor, capable of detecting and transforming all wavelengths of visible light into energy through photosynthesis.
“Each chlorosome in a green bacterium has a unique organization. They are like little andouille sausages. When you take cross-sections of andouille sausages, you see different patterns of meat and fat; no two sausages are alike in size or content, although there is some structure inside, nevertheless. Chlorosomes in green bacteria are like andouille sausages, and the variability in their compositions had prevented scientists from using X-ray crystallography to characterize the internal structure,” Bryant says.
“The interactions that lead to the assembly of the chlorophylls in chlorosomes are rather simple, so they are good models for artificial systems. You can make structures out of these chlorophylls in solution just by having the right solution conditions. In fact, people have done this for many years; however, they haven't really understood the biological rules for building larger structures. I won't say that we completely understand the rules yet, but at least we know what two of the structures are now and how they relate to the biological system as a whole, which is a huge advance,” the expert concludes.