Until now, scientists thought cyanobacteria were responsible for the earliest oxygenic photosynthesis, but new research suggests otherwise. Photo by Elsevier
March 6 (UPI) -- According to new research, ancient microbes were performing photosynthesis as much as one billion years earlier than previously thought.
Photosynthesis -- the ability to convert the sun's rays into usable energy, and in the process produce oxygen -- kickstarted early evolution, paving the way for more complex organisms. But scientists haven't been able to agree on when organisms first developed the ability.
Many scientists believe anoxygenic photosynthesis evolved earliest. Anoxygenic photosynthesis involves the splitting of hydrogen sulfide, or minerals such as iron, and doesn't produce oxygen. The theory holds that cyanobacteria capable of performing oxygenic photosynthesis, which split water and yields oxygen, came later, some 2.4 to 3 billion years ago.
The research of Tanai Cardona suggests otherwise.
Instead of searching for signs of oxygen in ancient rocks, the traditional method for finding ancient proof of photosynthesis, Cardona explored the biomechanical systems responsible for photosynthesis in primitive microbes -- so-called photosystems.
Both oxygenic and anoxygenic photosystems rely on an enzyme called Photosystem I, but core compositions of the enzyme are different in each system. Cardona hypothesized that if he could determine when the enzyme evolved two divergent functions, he could estimate when oxygenic photosynthesis first emerged.
His analysis, published this week in the journal Heliyon, showed the genetic differences first emerged 3.4 million years ago, before cyanobacteria are thought to have first arrived in the oceans.
"This is the first time that anyone has tried to time the evolution of the photosystems," Cardona said in a news release. "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."
As part of his research, Cardona measured the rate of evolution of photosystems from the emergence of cyanobacteria until today. When plotted backwards, the slow rate of evolution suggests photosystems first emerged before Earth was born. The calculations suggest photosystems may have evolved more rapidly when Earth was young and hot.
"There is still a lot we don't know about why life is the way it is and how most biological process originated," said. Cardona. "Sometimes our best educated guesses don't even come close to representing what really happened so long ago."