May 2012

From the ocean depths an ancient being rose…


No, not “Nessie.” But in my mind, something more exiting. Sometimes, the very first sentence of an the abstract hooks you… or at least hooks me. Check it out (emphasis mine):

Microbial communities can subsist at depth in marine sediments without fresh supply of organic matter for millions of years. At threshold sedimentation rates of 1 millimeter per 1000 years, the low rates of microbial community metabolism in the North Pacific Gyre allow sediments to remain oxygenated tens of meters below the sea floor. We found that the oxygen respiration rates dropped from 10 micromoles of O2 liter−1 year−1near the sediment-water interface to 0.001 micromoles of O2 liter−1 year−1 at 30-meter depth within 86 million-year-old sediment. The cell-specific respiration rate decreased with depth but stabilized at around 10−3 femtomoles of O2 cell−1 day−1 10 meters below the seafloor. This result indicated that the community size is controlled by the rate of carbon oxidation and thereby by the low available energy flux.

Wow. In English, the researchers report the analysis of an extremely slow-growing microbial community made of organisms that are potentially thousands (or maybe even millions) of years old, all living tens of meters below the ocean floor and kilometers under one of the most nutrient-starved regions of the Earth’s surface. This is all part of the story of one of the most extreme extremophiles I can think of.

The researchers did their research under the North Pacific Gyre. This is a nutrient-starved region. The image you want in your head is a garden turned bare because fertilizer was never used there. Because the North Pacific Gyre is one of the “barest gardens on Earth” there’s not much life-debris, in the form of carbon, falling out to the deeper parts of the ocean. This means the ocean floor gets very little of this carbon, and very little of it to be eaten by any critters living on or in the seafloor. That’s where these brave little bugs come into play.

Rarely fed any food at all by their algal gods from above, the organisms discovered by Røy, et al. are literally starving all the time. This means they don’t have energy for growth. Faced with this dilemma, they seem to have found a somewhat simple yet still shocking solution: don’t grow. Instead of survival by division, these microbes are either growing extraordinarily slowly, growing periodically (when “carbon mana” finally rains from the heavens), or are not growing at all and instead using what little energy they receive to repair molecular damage.

Beyond being fascinating and something straight out of a sci-fi novel, this is also work that has important consequences. It reinforces the inter-relatedness of ecosystems and the Earth across vast distances on the planet, as the starvation of these microbes is caused by the lack of growth in the surface ocean, in turn caused by ocean circulation patterns. And it also stands in support of emerging theories about the relationship between the size of an ecosystem and the energy available for maintenance of that ecosystem. Finally, it serves as yet another “WOW. Biology can do THAT?!” example that challenges our notions of habitability and expands the phase space for future searches for life on other worlds.

Not bad for some geezers in that have lived to see their “thousands” eh? (And it may be that calling them “thousands of years old” may be a polite yet drastic underestimation of their true age. Some think that at least some of these organisms may have lifespans in the millions of years.)

S. Domagal-Goldman Posted by
S. Domagal-Goldman
read more
  • jennifer

    ….deep… in the body of our earth where life is miracle

Pale Blue.blog
RSS Twitter Facebook
paleblue.you posts
Characterizing the “Missing Era” of Prebiotic Evolution
by Sara Imari Walker
Posted on: 13, Apr 2012
Water flows on the surface of Mars.
by Noah Hammond
Posted on: 11, Apr 2012
Found the Higgs… now find the aliens!
by Adi Chopra
Posted on: 4, Apr 2012
View more
post on paleblue.you
  • Astrobiology Magazine Top Story