2 Billion Year Old Rock Contains Living Microorganisms

The oldest living microorganisms ever found in rocks could be useful to scientists searching for life on other planets.

Scientists excavated a 2-billion-year-old rock in South Africa and surprisingly found that it contained groups of living, even thriving microorganisms , IFL Science reported on October 4. This is the oldest example of living microorganisms ever found in ancient rock .

Microbial cells in the cracks of a 2-billion-year-old rock sample, stained blue and analyzed. (Photo: Y. Suzuki/SJ Webb/M. Kouduka/Microbial Ecology).

"We don't know whether 2-billion-year-old rocks are still suitable for life. Before that, the oldest geological layer in which living microorganisms were found was a 100-million-year-old sediment layer on the ocean floor. So the new discovery is very exciting. By studying the DNA and genomes of such microorganisms, we can understand the evolution of early life on Earth," said Yohey Suzuki, an expert from the University of Tokyo, lead author of the new study published in the journal Microbial Ecology .

The microbe lived in a sealed fracture in ancient rock , excavated from the Bushveld Eruptive Complex – an intrusive rock formation formed when magma cools below the Earth's surface. The massive complex is almost the size of Ireland and contains some of the world's largest ore deposits, including around 70% of the world's mined platinum. It has remained relatively untouched since its formation, providing the perfect conditions for ancient microbes to survive. Such organisms live deep below the Earth's surface, evolve extremely slowly and have extremely slow metabolisms, meaning they can survive for a very long time in the eruptive rock – up to 2 billion years, according to the new study.

With support from the International Continental Scientific Drilling Program (ICDP), the team drilled down to a depth of 15 meters to retrieve a 30-centimeter core sample. Upon closer inspection, they discovered living microbial cells nestled closely together in cracks in the rock, isolated from the outside environment by clay-filled chambers.

To confirm that the microbes originated in the rock sample and were not newly introduced during drilling or testing, the team stained their DNA. They also used infrared spectroscopy to look at proteins inside the microbes and proteins in the surrounding clay. This allowed them to determine that they were alive and not newly introduced.

With the oldest living microorganisms ever found in rocks, the new discovery has huge implications. "I'm very interested in the existence of subsurface microorganisms, not only on Earth but also the potential to find them on other planets," Suzuki said.

Martian rocks are typically much older. "However, NASA's Perseverance rover is preparing to bring back rocks that are similar in age to the ones we used in our new study. Finding living microorganisms in samples from Earth that are 2 billion years old and being able to authenticate them makes me very excited about what we might find in Martian samples ," Suzuki added.