Microbiologists Find Living Microbes in 2-Billion-Year-Old Rock

Researchers from the University of Tokyo and elsewhere have found pockets of living microbes in mineral-filled veins within 2-billion-year-old rock from the Bushveld Igneous Complex, South Africa.

“We didn’t know if 2-billion-year-old rocks were habitable,” said Dr. Yohey Suzuki, a researcher at the University of Tokyo.

“Until now, the oldest geological layer in which living microorganisms had been found was a 100-million-year-old deposit beneath the ocean floor, so this is a very exciting discovery.”

“By studying the DNA and genomes of microbes like these, we may be able to understand the evolution of very early life on Earth.”

Dr. Suzuki and colleagues analyzed a rock sample from the Bushveld Igneous Complex, a rocky intrusion in northeastern South Africa that formed when magma slowly cooled below the Earth’s surface.

“The Bushveld Igneous Complex covers an area of approximately 66,000 km2 (roughly the size of Ireland), varies in thickness by up to 9 km, and contains some of the richest ore deposits on Earth including about 70% of the world’s mined platinum,” they said.

“Due to the way it was formed and minimal deformation or change occurring to it since then, the BIC is believed to have provided a stable habitat for ancient microbial life to continue until today.”

The core sample with a diameter of 8.5 cm and a length of 30 cm was obtained from a depth of 15.28 with the aid of the International Continental Scientific Drilling Program, a nonprofit organization that funds exploration at geological sites.

The rock was cut into thin slices and analyzed, which is when the team discovered living microbial cells densely packed into cracks in the rock.

Any gaps near these cracks were clogged with clay, making it impossible for the organisms to leave or for other things to enter.

The researchers built on a technique they had previously developed to confirm that the microbes were native to the rock sample, and not due to contamination during the drilling or examination process.

By staining the DNA of the microbial cells and using infrared spectroscopy to look at the proteins in the microbes and surrounding clay, they confirmed that the microorganisms were both alive and not contaminated.

“I’m very interested in the existence of subsurface microbes not only on Earth, but also the potential to find them on other planets,” Dr. Suzuki said.

“While Martian rocks are generally much older (20 billion to 30 billion years old), NASA’s Perseverance rover is currently due to bring back rocks that are a similar age to those we used in this study.”

“Finding microbial life in samples from Earth from 2 billion years ago and being able to accurately confirm their authenticity makes me excited for what we might be able to now find in samples from Mars.”

The results were published in the journal Microbial Ecology.

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Y. Suzuki et al. 2024. Subsurface Microbial Colonization at Mineral-Filled Veins in 2-Billion-Year-Old Mafic Rock from the Bushveld Igneous Complex, South Africa. Microb Ecol 87, 116; doi: 10.1007/s00248-024-02434-8

This article is based on a press-release from the University of Tokyo.