Mysterious desert bacterium has developed a unique ability for photosynthesis

(ORDO NEWS) — Photosynthesis literally changed our world. Plants, “eating” sunlight and “exhaling” oxygen, have transformed the entire atmosphere of the Earth into the one we now breathe, and provided energy to our ecosystems.

Now researchers have caught a cunning species of bacteria with stolen photosynthesis technology. And their molecular, light-eating device is unlike anything we’ve ever seen.

“The architecture of the complex is very elegant. A real masterpiece of nature,” says Michal Koblizek from the Institute of Microbiology of the Czech Academy of Sciences. “It has not only good structural stability, but also great light collection efficiency.”

Although we already know many photosynthetic bacteria, what happens inside the Gobi desert dweller Gemmatimonas phototrophica is unique.

Sometime in the course of its history, this bacterium stole a whole set of photosynthesis-related genes from an older Proteobacterium, a completely different phylum of bacteria.

This demonstrates the possibility of horizontal gene transfer in bacteria (notorious for spreading antibiotic resistance easily), allowing a completely different type of organism to gain the ability to feed on sunlight.

This new to science, highly stable, sunlight-capturing complex of molecules has a central reaction center, a sunlight-capturing inner ring previously seen in other bacteria, and a new type of outer ring.

Together, these three components make it larger than previously described photosynthetic complexes.

The outer rings capture sunlight, with the additional ring adding the 800 and 816 nm absorption bands to the 868 nm absorption of the inner ring. They then send the captured photons down to the reaction center, where the chromophores are located, like the green pigments of chlorophyll in plants.

This is where photosynthesis takes place. The captured sunlight excites the chromophores, causing them to transfer their electrons along a pathway that induces the water atoms into a series of reactions using carbon dioxide to produce sugars.

The particles of light become part of the bonding energy that binds the sugar molecules together – the very ones that we animals can then break down to create energy.

The reaction center of G. phototrophica is similar to those found in proteobacteria and has the same chromophores as those found in purple sunlight-eating bacteria. However, it differs from other known reaction centers in its unique arrangement of stabilizing molecules.

While this photosynthetic structure requires more energy to create than other more well-known types, the researchers explain, “this may be offset by its extraordinary stability, and the strength of the … complex is likely an evolutionary advantage.”

“This structural and functional study has exciting implications as it shows that G. phototrophica has independently evolved its own compact, rugged and highly efficient architecture for collecting and capturing solar energy,” says structural biologist Pu Qian from the University of Sheffield.

One day, we, in turn, may also be able to steal the ancient secrets of G. phototrophica photosynthesis to build the future of solar-powered synthetic biology.”


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