New technique traces the moment when life began to oxygenate the planet – The Clare People


Oxygen was essential for life on Earth to become complex and diverse, but during its first 2 billion years this element was scarce. Any organism that existed before this element rose to our planet survived on little or no oxygen – when and how this scenario changed are the answers scientists are looking for. In a new study, researchers say it took some bacteria 94 million years to photosynthesize sunlight and produce oxygen so that life could thrive.

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About 2.4 to 2.1 billion years ago, complex bacteria became capable of photosynthesis – that is, from sunlight they began to release oxygen in the Earth’s atmosphere – an event known as the Great Oxygenation Event (GEO), which changed the fate of evolutionary biology. The new study, conducted by scientists at the Massachusetts Institute of Technology (MIT), used a new technique that analyzes the genes of these organisms to chart a timeline.

In light green, cyanobacteria bloom near the surface (Image: Reproduction / NOAA / Toldeo Aerial Media)

According to estimates from In this research, it took bacteria at least 94 million years to become photosynthesized. Probably long before that, organisms capable of such a process already existed, but not in the same way as we know it today. MIT geobiologist and study lead author Greg Fournier explains that while there is evidence of oxygenated photosynthesis before then, it took hundreds of millions of years for oxygenation to take off.

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There are two main accounts that attempt to explain the evolution of photosynthesis from bacteria. The first understands that the natural process of transforming sunlight into energy arose at the very beginning of the evolutionary scenario, but it has progressed slowly. The second argues that the process appeared much later, but took off quickly. The divergence occurs due to different interpretations of the fossil record.


Cyanobacteria performing photosynthesis (Image: Reproduction / Dennis Nuernberg)

Rarely, when feeding on another organism, the bacteria can incorporate part of the genetic material into its genome. Through this, researchers can trace a timeline of these species and identify those that existed simultaneously – a process known as molecular clock modeling, which uses genetic sequences to trace possible changes in the genetic code over time. .

Fournier and his team therefore analyzed the genomes of thousands of bacteria – including cyanobacteria – to detect horizontal gene transfers. In total, the researchers identified examples of their molecular clock models, in which only one was reported. as more consistent. From there, the researchers estimated the age of the photosynthetic bacteria.

According to the study, all species of cyanobacteria that live today have a common ancestor, which existed around 2.9 billion years ago. Such an ancestor would have branched out from another bacterium unable to photosynthesize 3.4 billion years ago. Photosynthesis therefore arose somewhere between these two extremes. The researchers plan to use the same technique to analyze other organisms.

The research was published in September of this year, in the Proceedings of the Royal Society B.

Source: ScienceAlert

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