Scientists have found ancient organisms that were trapped in salt crystals 34,000 years ago. This was reported in a study published by The Geological Society of America’s open-access journal, GSA Today.
These ancient organisms that were found are called prokaryotes.
These are microbes which were known to exist in sub-surface habitats such as continental and oceanic crust as well as sub-seafloor sediments at depths of up to 3 km. Prokaryotes are single-celled organisms which do not have a nucleus or other membrand-bound specialised structures. They basically live in water within sediment pores and rock fractures. These organisms have also been found in glaciers that are up to 8 million years old.
According to the paper, “Collectively, these discoveries have extended the realm of the biosphere into Earth’s crust and have given hope for finding life beneath the surface of other planets, moons, asteroids, and comets of our solar system where present surface conditions are inhospitable.”
The researchers were Dr. Tim Lowenstein and Dr. Michael Timofeeff at the State University of New York at Binghamton, as well as Dr. Brian Schubert of the Univeristy of Hawaii at Manoa (who was then a Ph.D student at the State University of New York at Binghamton at the time of the study). These scientific researchers found that these organisms which were trapped in fluid inclusions, as in microscopic areas of water droplets, within salt crystals, and were able to grow them in a laboratory setting. Lowenstein said that these organisms were called arcaea, which was one of the 2 prokaryote domains, the other one being bacteria.
Timofeef added, “We were the first group to look inside the salts before we tried to culture microbes from them.”
According to Lowenstein, “They are trapped alongside a type of algae called Dunaliella, which just so happens to produce the food the archaea need to survive—the sugar alcohol glycerol.” This explains how they were able to survive for so long.
Light cannot enter the crystals, so the algae did not survive. The archaea were left only with whatever glycerol the algae had the exact moment they were trapped. As it was an isolated system, reproduction would have been difficult. This led the team of researchers to believe that these organisms that they found alive are the same ones that were trapped in the crystals 34,000 years ago – and not their descendants. Timofeef said, “They can reproduce, but at some point they will use up their available resources and conditions for life will become unfavourable.”
Compared with their modern-day counterparts, these ancient organisms are much smaller. “We believe this is evidence that the cells have moved into a starvation survival mode and miniaturised,” Timofeeff said. “When conditions for life become unfavourable, some microbes are able to move into a starvation survival mode and miniaturise.”
Other than these 34,000 year old ones, salt crystals that were 63,000 years old that contained microbes were also found. However, the researchers were unsure whether the organisms within them were still alive. “The only way we can be 100 percent sure that any microbe we observe inside of a fluid inclusion is alive is to give it conditions favourable for growth and see if it does,” Timofeeff said.
“There are a number of reasons why a microbe trapped inside an inclusion might not grow. The factors for survivability are not well known. We do know they should have enough glycerol to make it.”
The researchers stated that an earlier study claimed the finding of bacterium that was trapped in a crystal formed in the Permian period, which was 299 to 251 million years ago. However, this study was controversial as some believe that the bacterium was a contaminant from the laboratory.
“Although we are beginning to understand the community of micro-organisms inside modern and ancient fluid inclusions, much more needs to be learned about how they survive,” the researchers said in conclusion of their paper.
“Such knowledge will be vital as studies further explore deep life on Earth and elsewhere in the solar system, where materials that potentially harbour micro-organisms are millions and even billions of years old.”