• Laith Sharba

What Came First Oxygenic Photosynthesis or Anoxygenic Photosynthesis

Photo by Ivan Bandura on Unsplash

Scientists from Imperial College London studied the structure of a rare bacteria and found a similarity in the photosynthesis, this study suggests that the photosynthesis process is older than they assume.

These findings turned the traditional ideas on the scientists head now they have to rethink of the photosynthesis evolution.

By complex chemical reactions and the sun's light photosynthesis can produce nutrient to the plants and algae and unicellular organisms such as bacteria, if the water involving in this process we call it oxygenic photosynthesis because it use the H2O and split it to hydrogen and release the oxygen to the atmosphere, but if the water not involved organisms like bacteria use other chemical compounds to produce energy and don't release oxygen in this process.

The anoxygenic photosynthesis is a primeval process, that was the old idea and the scientists thought that the oxygen photosynthesis results from the evolution of anoxygenic photosynthesis but with these findings now they will think again. In matter fact, scientists think the anoxygenic photosynthesis emerged in 3.5 billion years ago and the oxygenic photosynthesis evolved from it about 1 billion years ago.

Imperial College researchers analyzed the internal structure in the ancient bacteria and they suggested that a primary step in oxygenic photosynthesis may be possible before the ordinary thought in a billion years ago.

You can find the research published in the journal "Trends in Plant Science".

Dr. Tanai Cardona from Imperial College life sciences department and the lead author of this study said that the researchers start to see most of the established evolution story of photosynthesis does not match with the data they gain about both of structure and function of early bacterial photosynthesis system.

The research team studied bacteria called Heliobacterium modesticaldum you can find it in soils and waterlogged fields, it also lives in hot springs where the possible conditions for anoxygenic photosynthesis. Another bacteria called cyanobacteria which is the main bacteria perform oxygenic photosynthesis scientists fount it very distantly related to H. modesticaldum.

Both types of bacteria are strongly related, H. modesticaldum share a common ancestor with cyanobacteria for billions of years ago. It means the features and merits in both types of them it should present in the original bacteria that gave rise to them.

Dr. Cardona found striking similarities when he analyzed the structure in H. modesticaldum and cyanobacteria and studied the different types of photosynthesis the preform.

Dr. Cardona noticed in both structures there is a specific site use to split water to oxygen and hydrogen, we can find this thing in plants and cyanobacteria which is a critical step in oxygenic photosynthesis.

Scientists always believed the cyanobacteria are the evolution of anoxygenic photosynthesis and it is the first appearance of the modern photosynthesis but this study showed H. modesticaldum has a similar site which means basic building blocks for oxygenic photosynthesis is much older than they thought.

This study suggests that the oxygenic photosynthesis has not resulted from the evolution of anoxygenic photosynthesis, it more as a trait evolved sooner if not came first.

Dr. Cardona said that this study help in understanding the details of the systems responsible for photosynthesis and oxygen production, but first we have to change the perspective of the way we see the evolution of photosynthesis.

Imperial College London. "Strange bacteria hint at ancient origin of photosynthesis." ScienceDaily. ScienceDaily, 25 July 2019. <www.sciencedaily.com/releases/2019/07/190725120556.htm>.

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