Tiny fossils that have been trapped inside chunks of ancient rock for some two billion years provide us with the earliest evidence of photosynthesis on Earth.
The McDermott Formation, located in the deserts of northern Australia, contains small structures called . Thylakoid Something thought to be fossilized has been discovered cyanobacteria It dates back to 1.75 billion years ago.
These structures are found within the cells of today’s photosynthetic organisms and contain the pigment chlorophyll, which is used to absorb light for photosynthesis.
This means that microfossils represent the oldest direct evidence of photosynthesis, and provides a new minimum age for the appearance of thylakoid-bearing cyanobacteria, as well as a new minimum age for the appearance of early terrestrial ecosystems and life on Earth. It gives us new tools to understand what is emerging.
“Our study provides direct evidence for the existence of metabolically active cyanobacteria that perform oxygenic photosynthesis.” A team led by paleomicrobiologist Catherine Dumoulin wrote: PhD from the University of Liege.
The discovery suggests that detailed analysis of other fossils may identify more similar structures, suggesting that photosynthetic structures were engulfed and put to work by the earliest forms of complex algal cells. It may be possible to pinpoint the exact moment in time.
Photosynthesis, which uses sunlight to convert water and carbon dioxide into glucose and oxygen, may seem like something a plant or algae is doing quietly over there, but it’s the basis of the survival of almost all living things. .
Not only do photosynthetic organisms form the basis of most food webs, but their metabolic processes fill the atmosphere with the breathable oxygen most of us need to survive.
We know that early in Earth’s history, there wasn’t much oxygen floating freely in the atmosphere and oceans. However, a variety of geochemical evidence revealed a sudden spike in oxygen levels. Approximately 2.4 billion years ago This is a phenomenon known as the Great Oxidation Phenomenon. The cause is unknown, but one possibility is the emergence of photosynthetic organisms.
The earliest incontrovertible microfossil evidence of cyanobacteria is an organism called. Eoentophysalis berherensisdate up to 2.018 billion years ago. However, fossils are often difficult to interpret, and their internal structures do not always remain intact. And not all cyanobacterial species have thylakoids.
Dumoulin and her colleagues used a variety of high-resolution microscopy techniques to investigate the external and internal structures of microfossils of a species known as . Nabyfusa magensis, is thought to be a cyanobacterium. They discovered thylakoid membranes in the bodies of single-celled organisms collected from two fossil beds.
These fossils are from the Grassy Bay Formation in Canada and are up to 1.01 billion years old. and the McDermott Formation, which dates back 1.75 billion years. This pushes the fossil record of thylakoids back a whopping 1.2 billion years, meaning that oxygenic photosynthesis must have evolved before then.
But what we don’t yet know is whether it evolved in time to contribute to the Great Oxidation event. Only by finding and carefully studying even old fossils will we get the answer to this burning question.
“Discovery of thylakoids stored in the body N. magensis The study reported here provides direct evidence for the divergence of thylakoid- and non-thylakoid cyanobacteria with a minimum age of approximately 1.75 billion years ago. ” the researchers write.
“We show that similar ultrastructural analyzes of well-preserved microfossils may expand the geological record of early weakly oxygenated ecosystems, where oxygenated photosynthetic apparatuses and complex cells developed. We predict that there will be.”
This research Nature.