An article published in the journal “Trends in Plant Science” reports a deveolpment of a theory on the evolution of photosynthesis. Tanai Cardona and A. William Rutherford of Imperial College London studied various bacteria belonging to species capable of photosynthesis. Their conclusion is that the photosynthesis we know today thanks to plants was possible much earlier than previously thought and wasn’t an evolution of another form that is generally considered more primitive and doesn’t lead to the release of oxygen.
Photosynthesis, which is the ability of organisms such as plants to use solar energy to produce sugars and emit oxygen, is well known but is extended to groups of algae and bacteria. That’s not the only form of photosynthesis existing since there are bacteria capable of a form that use molecules other than water to power it and doesn’t emit oxygen.
According to a reconstruction, originally the anoxygenic photosynthesis form was common among bacteria and we’re talking about really primitive bacteria because that capacity could have appeared at least 3.5 billion years ago, perhaps even 3.8 billion years ago, so more or less with the first life forms that we could define as bacteria. According to this reconstruction, the oxygenic form we commonly know evolved a long time later.
Dr. Tanai Cardona already conducted research on the evolution of photosynthesis: in an article published in “PLOS ONE” in March 2016 he addressed the problem of its diversification while in an article published in “Heliyon” in March 2018 he also addressed the problem of the origin of oxygenic photosynthesis. In the new article published in “Trends in Plant Science” together with his colleague A. William Rutherford he develops the theory that oxygenic photosynthesis could have been possible even a billion years earlier than previously thought.
The researchers analyzed the bacteria of the species Heliobacterium modesticaldum (image courtesy Madigan et al.), which are found in environments such as hot springs and are capable of anoxygenic photosynthesis, and compared their structures to the ones that modern cyanobacteria use for oxygenic photosynthesis. Cyanobacteria are considered the first ones capable of oxygenic photosynthesis but have in common with Heliobacterium modesticaldum structures capable of breaking water’s molecular bonds, crucial in oxygenic photosynthesis.
According to Dr. Tanai Cardona, the discovery of structures common to such different bacteria species suggests that oxygenic photosynthesis may have evolved much earlier than previously thought, in parallel if not even before the anoxygenic version. He thinks that the idea that oxygenic photosynthesis evolved from the anoxygenic one isn’t based on facts and according to his reconstructions it could have appeared even 3.6 billion years ago.
The research of Dr. Tanai Cardona shows that the history of a chemical process that marked the history of life on Earth may require a change of perspective to be understood. The genetic studies possible with today’s instruments will help to answer the questions that still exist and to reconstruct phases of the evolution of life that hugely influenced the planet and all subsequent history.
