New Extremophiles: possible means of evolution (Introduction)

by David Turell , Tuesday, January 30, 2018, 15:50 (2292 days ago) @ dhw

New studies on one form suggest ways they may have evolved to less extreme environments. Most extremophiles are archaea and relate to original life:

https://www.sciencedaily.com/releases/2018/01/180126085437.htm

"Extremophiles -- hardy organisms living in places that would kill most life on Earth -- provide fascinating insights into evolution, metabolism and even possible extraterrestrial life. A new study provides insights into how one type of extremophile, a heat-loving microbe that uses ammonia for energy production, may have been able to make the transition from hot springs to more moderate environments across the globe. 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.

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"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?"

"As a starting point to answer this question, Professor Schleper and her team isolated a Thaumarchaeota species from a hot spring in Italy then sequenced and analyzed its genome. This represents the first genome analysis of the Nitroscaldus lineage -- a subgroup of heat-loving Thaumarchaeota that get their energy by oxidizing ammonia into nitrite.

"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."

"Many researchers assume that the first life forms on Earth evolved in hot springs. Further studies of this thermophile archaeon might help identify general mechanisms that enabled the first living cells, both bacteria and archaea, to conquer the world."

Comment: Hot springs and hot vents in oceans certainly are appealing as points of origin of life, and the possibility horizontal gene transfer plays a major role in evolution at this stage, as suggested by this study, is intriguing. See this:

https://cosmosmagazine.com/biology/did-extremophiles-move-into-less-nasty-habitats-by-h...

"The team found that N. cavascurensis is most closely related to the last common ancestor of all Thaumarchaeota, a position in the lineage that can provide crucial information into the evolution of early life. Importantly, N. cavascurensis displays various features that are not typical of thermophilic archaea, including the integrated DNA of an ancient virus (known as a provirus), indicating an evolutionary move toward more moderate environments.

"N. cavascurensis’ genome also contains numerous mobile genetic elements that are implicated in “lateral gene transfer”, which is the movement of genetic material between existing organisms, rather than from parent to offspring, and this provides a clue to how they spread beyond extreme environments.

“'This organism seems prone to lateral gene transfer and invasion by foreign DNA elements,” says 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 neighbouring organisms in its hot spring.'”

Comment: How much of the evolution of early life was by chance Darwinian mutation? Horizontal gene transfer could be God manipulating the mechanism.