Dinosaur bones are home to microscopic life

Bad news, fans of Jurassic Park: the chances of scientists cloning a dinosaur from an old DNA are almost nil. Indeed, the DNA breaks down over time and is not stable enough to remain intact for millions of years. And while proteins, the molecules in all living things that structure and help the body to function, are more stable, even though they may not be able to survive longer than tens or even hundreds of millions of dollars. ; years. In a new article published in eLifeScientists have been searching for preserved collagen, the protein found in bones and skin, in dinosaur fossils. They did not find the protein, but they found huge colonies of modern bacteria living inside dinosaur bones.

"This is an innovation – this is the first time we have discovered this unique microbial community in these fossil bones as they are buried underground," says lead author Evan Saitta, a postdoctoral researcher at the Field Museum. "And I would say that it is another nail in the coffin in the belief that dinosaur proteins remain intact.

Saitta began her research on organic molecules in fossils as part of her doctoral dissertation at the University of Bristol. "My doctoral work was on how the soft tissues become fossilized and how these materials decompose, some molecules can survive in the fossil record, but I suspect that the proteins can not, they are unstable on these scales. time in fossilization conditions, "says Saitta.

However, some paleontologists have reported finding dinosaur bones containing exceptionally preserved traces of collagen proteins, as well as soft tissues such as blood and bone cells. "These supposed dinosaur proteins have sparked renewed interest," Saitta said. So, he undertook to independently test the presence of collagen in dinosaur fossils.

Saitta has taken the trouble to collect dinosaur fossils under as sterile conditions as possible, so that new proteins or bacteria are not introduced into the fossils and distort the results. He brought a pick, a saw, a blowtorch, ethanol and bleach to Dinosaur Provincial Park, Alberta, Canada.

"There is only one layer where there is practically more bone than rock, bone concentration is ridiculous," says Saitta. A site with a lot of bone was the key, as a slow, winding search would open the fossils more likely to be contaminated by the surface world. "To collect these bones in a very controlled and sterile manner, you need a dig site with a ton of bone because you have to find the bone quickly, exposing just enough of one." tip to find out what it is, then aseptically collect the unexposed drill from the bone and surrounding rock all in one ". Saitta collected fossils dating back 75 million years from Centrosaurus – a small cousin of Triceratops – and then brought the bones back to various laboratories to examine its organic composition.

Saitta and colleagues compared the biochemical composition of Centrosaurus fossils with modern chicken bones, sediments from the fossil site in Alberta, and thousands of years old shark teeth stranded on the city's coast. from Ponte Vedra Beach, his hometown, of Saitta. . "We visited several laboratories and the different techniques allowed us to obtain consistent and easy to interpret results, suggesting that aseptic collection was sufficient," says Saitta. They discovered that the Centrosaurus fossils did not seem to contain the collagen proteins found in fresh bones or in much younger shark teeth. But they found something else: "We see a lot of evidence of recent microbes," says Saitta. "There is clearly something organic in these bones." And because laboratory work indicates that Saitta's anti-contamination measures have worked, these organic materials have to go naturally.

"We have found non-radiocarbon dead organic carbon, recent amino acids and DNA in the bone, indicating that the bone is home to a modern microbial community and is a safe haven," he said. said Saitta. He thinks, as others have already suggested, that modern microbes and their secretions, called biofilms, are probably what other researchers have seen in fossils and described as soft tissues of dinosaurs. "I suspect that if we started doing this type of analysis with other specimens, it would explain some of the so-called soft tissue dinosaur findings," he says.

Surprisingly, modern microbes present in dinosaur bones are not quite the same mundane bacteria living in the surrounding rock. "It's a very unusual community," says Saitta. "Thirty percent of the sequences are related to Euzebya, which is reported only from places such as Etruscan tombs and sea cucumber skin, to my knowledge."

Saitta and her colleagues do not really know why these microbes live in the bones of dinosaurs, but it's not surprising that bacteria are attracted to fossils. "The fossil bones contain phosphorus and iron, and the microbes need them as nutrients, and the bones are porous, they absorb moisture.If you were a living bacterium in the soil, you would probably want to live in a dinosaur bone, "he added. said. "These bacteria clearly spend a very good time in these bones."

The discovery could help advance the emerging field of molecular paleontology, says Saitta. "It's one of the new frontiers of modern paleontology. We are starting to undertake a very different type of fossil hunt. We are not only looking for bones and teeth, we are hoping to find new species, we are hunting for molecular fossils. opens a whole new set of evidence to study life in the past. Molecular fossils can tell us things that we never thought we could study. It is important to distinguish what is modern from what is old is old. "