Winning the Genetic Diversity Race in Lost City


Image: D. Kelley of University of Washington, IFE, URI‑IAO, UW, Lost City science party, NOAA
Lost City of Atlantis
The Lost City is so named because it juts from an Atlantic undersea mountain named Atlantis and was coincidentally discovered by the scientific expedition aboard the research vessel Atlantis. Scientists who noticed the white columns growing 65 to 200 feet up from the ocean floor were soon credited with finding a completely new type of hot spring environment. Previously, the only hot springs known derived their heat from the hot magma below the earth's crust.

But the Lost City represents a remarkable chemical process that may now be providing the best empirical evidence for the widely believed theory that when conditions change, relatively rare indigenous species may quickly take over and dominate a biosphere at the expense of previously successful species. The Remarkable Chemistry of Life
The Lost City Hydrothermal Field benefits from a fantastic chemistry that some scientists believe may point to the origin of life on earth. The mere contact of seawater with the underlying rock suffices to drive a series of processes that provide three essential criteria for a microbial Garden of Eden:

  1. It is a unique type of rock, peridotite, which is normally found only much deeper in the earth, but which juts up to the mantel in the Atlantic massif. Peridotite reacts with seawater, generating heat: ingredient number one for the success of life. Even more important, the heat raises the surrounding waters to only moderate temperatures (around 200°F), as opposed to the scorching hot waters vented from magma-heated springs.
  2. The reaction results in a reduced form of the metal iron, which can use the power of chemical reduction to turn carbon in the nearby rock into hydrocarbons. These carbon and hydrogen chains are the raw material for cell walls and the starting material for the creation of amino acids, the alphabet of proteins.
  3. Finally, the reaction leaves behind a highly alkaline warm solution, between pH 9 and 11, which when vented precipitates carbonate from the seawater, building white carbonate limestone-like "chimneys" that can grow to great heights. The tallest chimney, named Poseidon, is 18 stories tall.
Thus, a beautiful white and cream domicile grows where, even if life did not originate from the unique chemical soup at the hydrothermal vents, microbes find themselves perfectly at home. It is this 30,000 year old home-sweet-home that has yielded the proof of the 'rare biosphere' hypothesis.

Winning the Genetic Race
Invasive species hint at what is possible in evolution's race. Benefiting from a lack of competition or predation, invasive species are increasingly proliferating in environments where they are quite unwelcome. Asian carp in the Mississippi and African rock pythons eating goats in Florida come to mind.

But the 'rare biosphere' model being tested in the undersea Lost City has a different premise: an environment is dominated by the successful species, but important genetic material is preserved in rare members of the biosphere -- genetic memory that may be exactly what is needed to win the survival race if conditions change.

Scientists initially thought that traces of odd DNA found when analyzing microbial communities were simply artifacts of the DNA sequencing process. But the evolution of DNA sequencing techniques has now made it clear that a large number of microbes exist that are represented only by rare, remaining members of their type. What are so many almost-extinct microbes doing hanging about in otherwise thriving communities?

That is the question that authors of a study published this week in the Proceedings of the National Academy of Sciences believe they have answered. Led by William Brazelton, a postdoctoral researcher at the University of Washington, the team showed that microbes that are quite rare in some vents are the dominant population in other vents. The "winning genes" depend on the temperature and other conditions that change over time as the vents age and grow. The authors conclude:

The rare biosphere of the Lost City microbial community represents a large repository of genetic memory created during a long history of past environmental changes. The rare organisms were able to rapidly exploit the new niches as they arose because they had been previously selected for the same conditions in the past.

Genetic Memories of Warmer Climes
There is a branch of denialism in the face of global warming studies that responds by pointing out that even if global warming is occurring, and even if it is anthropogenic (caused by man), it doesn't matter. The earth will survive, life will go on; it always does. Studies like this confirm the robustness of life in the face of inevitable change. But it sure would be nice if some of the fun species could stick around: like dogs and dolphins, toads and tigers, hummingbirds and humans. How will the genetic memory locked in the cells of all species steer the future of life as conditions change? Which are the rare species among us that will dominate the world after warming?

More on Genetic Diversity:
TreeHugger Forums: "2010- International Year of Biodiversity"
http://www.treehugger.com/files/2008/06/usda-climate-change-super-weeds.php
What Happens to Cold Blooded Animals in a Warming World (Slideshow)
The World's Most Lovable Invasive Species

Tags: Biology | Endangered Species | Evolution | Oceans

Best of TreeHugger