The world's oldest microorganisms
Is there a limit to microbial life?
Microorganisms require oxygen to maintain the electrical potential in the membranes, as well as the work of enzymes and DNA, so researchers believe that these inhabitants of the seabed are able to live with minimal access to energy. And indeed, scientists describe a community that is 86 million years old, although for many years experts believed that high pressure, lack of oxygen and low amounts of nutrients under the seabed should have been a severe test for any form of life.
The Northern Pacific Current, together with its southern counterpart, represent the most nutrient-poor areas of the World Ocean. However, Mr. Ray and his colleagues found that oxygen penetrates into the sediment there to a depth of up to 28 m. The researchers concluded that the reason for this mysterious phenomenon should be considered a low deposition rate.
Hans Ray at work (here and below photo by Bo Barker Jorgensen / Science / AAAS).
The sediment accumulates so slowly that if one particle sinks to the bottom, the other falls on it only after a thousand years. In such conditions, microorganisms eat almost everything, and when there is no food, they just hang around surrounded by oxygen, not consuming it. The turnover of biomass occurs only once every few hundred or even thousands of years.
Usually, microorganisms consume all the oxygen in the upper 10-centimeter layer of sediment, and switch to other compounds below. But in this case, the microbial community is so small that it is not able to consume all available oxygen even at a 28-meter depth. The researchers found out that at a depth of more than 20 m, microorganisms contained in one cubic meter of silt need about ten years to use up the amount of oxygen contained in one human breath.
The discovery of this life form prompted the Center for Geomicrobiology of Aarhus University and the Astrobiology department of the NASA Research Center. Ames organized a conference of geomicrobiologists and computer model developers on the study of the limits of microbial life and biological demand for energy, which took place last week in Aarhus.
"The boundaries of life lie much further than we could have imagined," says co—organizer Bo Jorgensen. — Apparently, we have met with an energy limit located below our current understanding. And we have to admit that we don't know where the lower bound might be."
That's why NASA was interested in the discovery. The surface of Mars is inhospitable, but underneath it, says Mr. Jorgensen, "there may be conditions that resemble the depths of the earth in terms of the flow of available energy." "This study has shown that life can exist even in such conditions," the specialist summarizes.
Mr. Jorgensen emphasizes that this, of course, does not mean that there is life on Mars, but admits that "it is very difficult to say where there is no life right now."
The core of the Pacific sediment, extracted by researchers.
The results of the study are published in the journal Science (Aerobic Microbial Respiration in 86-Million-Year-Old Deep-Sea Red Clay).
Prepared by Nature News (Slo-mo microbes extend the frontiers of life)
and ScienceNOW (Barely Breathing Microbes Still Living in 86-Million-Year-Old Clay).
Portal "Eternal youth" http://vechnayamolodost.ru18.05.2012