March 8th, 2013 by James Ayre
How does a form of life go about becoming capable of surviving in the world’s most extreme environments? How does something go about developing resistance to extreme heat, acidity, and exposure to toxic heavy metals? By stealing the genes that allow those capabilities from their neighbors, apparently.
The “extremophile” red alga Galdieria sulphuraria is able to survive, even thrive, in a strangely varied collection of environments. When living in the extreme living environment of Yellowstone National Park’s hot springs, Galdieria gets energy its energy from photosynthesis. When living in the pitch black of old mineshafts, in drainage that is as caustic as battery acid, it lives as a predator feeding on bacteria. And is somehow able to survive very high concentrations of arsenic and other heavy metals.
It’s a strange collection of traits that allow survival in such varied and extreme environments. How does a one-celled alga acquire these traits?
Looking to answer that question, researchers from Oklahoma State University and Heinrich-Heine-Universitat (Heinrich-Heine University) in Dusseldorf, Germany, completely decoded the genome of Galdieria.
After doing so, they discovered something unexpected, “Galdieria’s genome shows clear signs of borrowing genes from its neighbors. Many genes that contribute to Galdieria’s adaptations were not inherited from its ancestor red algae, but were acquired from bacteria or archaebacteria.”
This is referred to as “horizontal gene transfer”, it is very common in bacteria, but has also been observed in more complex organisms such as humans.
“However, Galdieria is the first known organism with a nucleus (called a eukaryote) that has adapted to extreme environments based on horizontal gene transfer.”
“The age of comparative genome sequencing began only slightly more than a decade ago, and revealed a new mechanism of evolution–horizontal gene transfer–that would not have been discovered any other way,” says Matt Kane, program director in the National Science Foundation’s (NSF) Division of Environmental Biology, which funded the research.
“This finding extends our understanding of the role that this mechanism plays in evolution to eukaryotic microorganisms.”
The tolerance for extreme heat that Galdieria possesses appears to come from genes that are present in the hundreds in its genome, but very likely all descending “from a single gene the alga copied millions of years ago from an archaebacterium.”
“The results give us new insights into evolution,” Schoenknecht says. “Before this, there was not much indication that eukaryotes acquire genes from bacteria.”
“The alga owes its ability to survive the toxic effects of such elements as mercury and arsenic to transport proteins and enzymes that originated in genes it swiped from bacteria. It also copied genes offering tolerance to high salt concentrations, and an ability to make use of a wide variety of food sources. The genes were copied from bacteria that live in the same extreme environment as Galdieria.”
“Why reinvent the wheel if you can copy it from your neighbor?” asks Lercher.
“It’s usually assumed that organisms with a nucleus cannot copy genes from different species–that’s why eukaryotes depend on sex to recombine their genomes.
“How has Galdieria managed to overcome this limitation? It’s an exciting question.”
What Galdieria did is “a dream come true for biotechnology,” says Weber.
“Galdieria has acquired genes with interesting properties from different organisms, integrated them into a functional network and developed unique properties and adaptations.”
That’s practically the holy grail of what biotechnology is attempting. Though it very well may not possible for humans to do such a thing, much less do so with out unexpected and potentially devastating consequences. Damage to the natural ecosystems that humans are still entirely dependent upon, agriculture, or human health, are all possibilities when things that typically occur over very time periods, and within the framework of a highly completive natural world, are forced to occur based solely on the ideas, goals, and conceptions of individual humans.
With regards to this individual discovery, the researchers think that it may open up possibilities for the biofuel industry.
The new research was just published in this week’s issue of the journal Science.
Source: National Science Foundation
Image Credits: Christine Oesterhelt
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