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Researchers: Horizontal gene transfer may have helped early microbes move out of hot springs

halobacterium, an archaean

The microbes are archaea, not bacteria. From ScienceDaily:

The first-ever analysis of DNA of a contemporary heat-loving, ammonia-oxidizing organism, published in open-access journal Frontiers in Microbiology, reveals that evolution of the necessary adaptations may have been helped by highly mobile genetic elements and DNA exchange with a variety of other organisms.

Most extremophiles are microorganisms — and many of the most extreme are archaea, an ancient group of single-celled organisms intermediate between the other two domains of life, bacteria and eukaryotes. Different archaea lineages are specialized to different extreme environments, including scalding hot springs, incredibly salty lakes, sunless deep-sea trenches and frigid Antarctic deserts. Only one branch, Thaumarchaeota, has managed to colonize very successfully the Earth’s more hospitable places — but scientists don’t know why.

“Thaumarchaeota are found in very large numbers in virtually all environments, including the oceans, soils, plant leaves and the human skin,” says Professor Christa Schleper from the University of Vienna, Austria, who guided and initiated the study. “We want to know what their secret is: billions of years ago, how did they adapt from hot springs, where it seems all archaea evolved, to more moderate habitats?”

The analysis revealed that the organism, Candidatus Nitrosocaldus cavascurensis, seems to represent the closest-related lineage to the last common ancestor of all Thaumarchaeota. Intriguingly, it has highly mobile DNA elements and seems to have frequently exchanged DNA with other organisms — including other archaea, viruses and possibly even bacteria.

The ability to exchange genetic material could help this archaeon to rapidly evolve. “This organism seems prone to lateral gene transfer and invasion by foreign DNA elements,” says Professor Schleper. “Such mechanisms may have also helped the ancestral lines of Thaumarchaeota to evolve and eventually radiate into moderate environments — and N. cavascurensis may still be evolving through genetic exchange with neighboring organisms in its hot spring.” Paper. (public access) – Sophie S. Abby, Michael Melcher, Melina Kerou, Mart Krupovic, Michaela Stieglmeier, Claudia Rossel, Kevin Pfeifer, Christa Schleper. Candidatus Nitrosocaldus cavascurensis, an Ammonia Oxidizing, Extremely Thermophilic Archaeon with a Highly Mobile Genome. Frontiers in Microbiology, 2018; 9 DOI: 10.3389/fmicb.2018.00028 More.

Note:  Archaea explained. Extremophiles explained.

Reading between the lines, we don’t know for sure that horizontal gene transfer (lateral gene transfer) occurred here. But if it did, that makes way more sense than asking us to close our eyes and imagine everything happening in a purely Darwinian way (natural selection acting on random mutation), with probability cast to the winds. And if “N. cavascurensis may still be evolving through genetic exchange with neighboring organisms in its hot spring…”

File with: Firewood! More branches are falling from Darwin’s fabled tree of life, where all evolutionary relationships are ancestor-descendent ones.

See also: (Real non-Darwinian) evolution in action: Bacteria murder rivals and steal their genes

Researchers ask: Do viruses share genes across the kingdoms of life?


Horizontal gene transfer: Sorry, Darwin, it’s not your evolution any more


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