New Oxygen research;photosynthesis early appearance? (Introduction)

by David Turell , Tuesday, March 06, 2018, 19:24 (2244 days ago) @ David Turell

A new genome study suggests photosynthesis appeared a billion years earlier than thought:

https://www.sciencedaily.com/releases/2018/03/180306093304.htm

"The earliest oxygen-producing microbes may not have been cyanobacteria.

"Ancient microbes may have been producing oxygen through photosynthesis a billion years earlier than we thought, which means oxygen was available for living organisms very close to the origin of life on earth. In a new article in Heliyon, a researcher from Imperial College London studied the molecular machines responsible for photosynthesis and found the process may have evolved as long as 3.6 billion years ago.

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"Previously, scientists believed that anoxygenic evolved long before oxygenic photosynthesis, and that the earth's atmosphere contained no oxygen until about 2.4 to 3 billion years ago. However, the new study suggests that the origin of oxygenic photosynthesis may have been as much as a billion years earlier, which means complex life would have been able to evolve earlier too.

"Dr. Cardona wanted to find out when oxygenic photosynthesis originated. Instead of trying to detect oxygen in ancient rocks, which is what had been done previously, he looked deep inside the molecular machines that carry out photosynthesis -- these are complex enzymes called photosystems. Oxygenic and anoxygenic photosynthesis both use an enzyme called Photosystem I. The core of the enzyme looks different in the two types of photosynthesis, and by studying how long ago the genes evolved to be different, Dr. Cardona could work out when oxidative photosynthesis first occurred.

"He found that the differences in the genes may have occurred more than 3.4 billion years ago -- long before oxygen was thought to have first been produced on earth. This is also long before cyanobacteria -- microbes that were thought to be the first organisms to produce oxygen -- existed. This means there must have been predecessors, such as early bacteria, that have since evolved to carry out anoxygenic photosynthesis instead.

"'This is the first time that anyone has tried to time the evolution of the photosystems," said Dr. Cardona. "The result hints towards the possibility that oxygenic photosynthesis, the process that have produced all oxygen on earth, actually started at a very early stage in the evolutionary history of life -- it helps solve one of the big controversies in biology today.'"

Comment: Even if oxygen arrived that early, at 3+ billion years ago, and is necessary for life as we know it, the Cambrian Explosion which relates to higher oxygen levels, is only 540 million years ago. Cyanobacterial production is still very important as a major source of oxygen in the atmosphere.