A new study by the Bigelow Ocean Science Laboratory, USA, showed that the Candidatus Desulforudis audaxviator group of microbes had been in evolutionary stagnation for millions of years.
New research has shown that a group of bacteria that exist through chemical reactions caused by radioactivity have been in evolutionary stagnation for millions of years. The discovery could have important implications for biotechnology applications and the scientific understanding of microbial evolution.
“The finding shows that we must be careful when making assumptions about the rate of evolution and how we interpret the tree of life,” said Eric Beckcraft, lead author of the article. “This will make it difficult to establish reliable molecular timelines.”
Beckraft, now an assistant professor of biology at the University of North Alabama, completed the research as part of his doctoral work in Bigelow’s lab and recently published it in the ISME journal of the Nature publishing group.
The bacterium Candidatus Desulforudis audaxviator was first discovered in 2008 by a group of scientists led by Tallis Onstott, co-author of the new study. They were found in a South African gold mine almost two miles from the surface of the Earth. There they receive the energy they need due to chemical reactions caused by the natural radioactive decay of minerals. They live in water-filled cavities inside rocks in a completely independent ecosystem, free from sunlight or any other organisms.
Because of their unique biology and isolation, the new study’s authors wanted to understand how bacteria evolved. They examined other environmental samples deep underground and found Candidatus Desulforudis audaxviator in Siberia and Death Valley in California and several South African mines. Each environment was chemically different. This gave scientists a unique opportunity to look for differences that have arisen between populations over millions of years of their evolution.
“We wanted to use this information to understand how they evolved and what environmental conditions lead to what genetic adaptations,” explains Ramunas Stepanauskas, senior researcher at Bigelow lab and author of the article. “We thought of bacteria as if they were inhabitants of isolated islands. like the finches that Darwin studied in the Galapagos Islands. ”
Using advanced tools, the researchers examined the genomes of 126 bacteria sourced from three continents. Surprisingly, they all turned out to be almost identical.
Scientists have found no evidence that microbes can travel long distances, survive on surfaces, or live long in the presence of oxygen. So, once the researchers determined that there was no possibility of cross-contamination of the samples during the study, there were fewer plausible explanations.
“The best explanation we have at the moment is that these microbes have not changed much since they moved during the disintegration of the Pangea supercontinent about 175 million years ago,” concludes Stepanauskas. “They seem to be living fossils of those days. This sounds pretty crazy and contradicts the current understanding of the evolution of bacteria. ”
Many well-studied bacteria, such as E. coli, evolve in just a few years in response to environmental changes such as exposure to antibiotics.
Stepanauskas and colleagues speculate that the stationary evolution they discovered is associated with a powerful defense against a mutation of microbes that essentially blocked their genetic code.