Living microbes found sealed in rocks for two billion years

Deep underground, in the darkness far from the bustling activity on the surface, a community of microbes lives their best lives in isolation.

What makes these organisms so incredibly special is that they have been extinct for billions of years – far longer than any other community of subterranean microbes we have ever seen. This discovery of living microbes in a 2-billion-year-old rock breaks the previous record of 100 million years.

“So this is a very exciting discovery,” says microbiologist Yuhei Suzuki From the University of Tokyo.

This is important: Microbes found in isolated underground pockets like these tend to evolve more slowly, because they are separated from many of the pressures that drive evolution in more densely populated habitats.

This means that the microbial community could tell us things we may not have known about the evolution of microbes here on Earth. But it also suggests there may be underground microbial communities that are still alive MarsIt remains alive long after the water on the surface dries.

“We didn’t know if two-billion-year-old rocks were habitable.” Suzuki explains.

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

The rock sample was drilled from 15 meters (50 feet) underground from a formation known as Bushveld igneous complex In northeastern South Africa. The formation is massive, penetrating 66,000 square kilometers (25,500 square miles) into the Earth’s crust that formed about 2 billion years ago from the cooling of molten magma beneath the surface.

Suzuki and his colleagues believed that rock formation and evolution over time would likely lead to long-term habitation by microbes. They enlisted the help of the International Continental Scientific Drilling Program to extract a 30-cm (1-foot) core from within the Bushveld volcanic complex, and began searching for signs of microbial life.

First, they had to rule out that any microbes they found were native to the habitat, and not the result of contamination from the extraction process. They used a technique they developed several years ago which includes Sterilize the outside of the sample Before cutting it into slices to examine its contents.

Then they used A Cyanine dye To color slides. This dye binds to DNA, so if there is any DNA in the sample, it should light up like a Christmas tree when subjected to infrared spectroscopy. And that’s exactly what happened.

The sample was also full of clay, filling veins near pockets in the rock near microbial colonies.

The result of this clay mobilization was multifaceted: it provided a resource for microbes to live on, with organic and inorganic materials they could metabolize; The rocks were effectively sealed, preventing microbes from escaping, and preventing anything else from getting in – including drilling fluid.

The microbial community in the rock will need to be analyzed in more detail, including DNA analysis, to determine how it may or may not have changed during the two billion years it was isolated away from the rest of life on Earth.

The team will collect more samples from the Bushveld Igneous Complex to help characterize the microbes that can be found there, and fit them into the Earth’s evolutionary history.

Of course, there are implications for what we might find beyond Earth.

“I’m very interested in the existence of subsurface microbes, not only on Earth, but also the possibility of finding them on other planets.” Suzuki says.

“NASA’s Mars rover is currently scheduled to return rocks with a similar age to the ones we used in this study. Finding microbial life in samples from Earth two billion years ago and being able to precisely confirm its authenticity makes me excited about what we may now be able to find.” On samples from Mars.

The research was published in Microbial environment.