Living microbes have been found deep beneath the seafloor.
Image: NOAA/WHOI
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For the first time, scientists have discovered microbes living deep inside Earth’s oceanic crust — the dark volcanic rock at the bottom of the sea. This crust is several kilometers thick and covers 60% of the planet’s surface, making it the largest habitat on Earth.
The microbes inside it seem to survive largely by using hydrogen, formed when water flows through the iron-rich rock, to convert carbon dioxide into organic matter. This process, known as chemosynthesis, is distinct from photosynthesis, which uses sunlight for the same purpose.
Chemosynthesis also fuels life at other deep-sea locations such as hydrothermal vents, but those are restricted to the edges of continental plates. The oceanic crust is much bigger. If similar microbes are found throughout it, the crust “would be the first major ecosystem on Earth to run on chemical energy rather than sunlight”, says Mark Lever, an ecologist at Aarhus University in Denmark, who led the study. The results are published in Science.
“This study is highly significant in that it confirms the existence of a deep-subsurface biosphere that is populated by anaerobic microorganisms,” says Kurt Konhauser, a geomicrobiologist at the University of Alberta in Edmonton, Canada.
The oceanic crust is formed at ridges between tectonic plates, where rising lava meets sea water and cools. The newborn rock — mostly basalt — is pushed away from the ridges and becomes buried under thick sediment. Although scientists have long known that microbes live in this sediment and in exposed basalt that has not yet been covered, the deeper, buried parts of the crust have been a mystery. “Until our study it still wasn’t clear that there’s life down there,” says Lever.
Under the sea
In 2004, Lever sailed aboard the US research vessel JOIDES Resolution to collect samples from one of the best-studied regions of oceanic crust, just west of Washington state. The ship usually carries a crew of geologists, but this time, “we had five microbiologists on board”, says Lever.
The team, which included scientists from six different countries, drilled through 265 meters of sediment and 300 meters of crust to collect basalt that had been formed around 3.5 million years ago. Inside their samples, the researchers found genes from microbes that metabolize sulphur compounds and some that produce methane.
To test whether the genes came from living or long-dead microbes, the team heated the rock samples to 65 °C in water rich in chemicals found on the sea floor. Over time, methane was produced, showing that the microbes were living and growing.
Lever is convinced that the microbes are not hitchhikers from the surface, but genuine residents of the crust. “When I went on this expedition, I thought it would be impossible to get contamination-free samples,” he says. He changed his mind after cracking open the samples: the team had added small amounts of marker chemicals to the fluid they used to drill for samples, but although these chemicals slathered the exterior of the rocks, there was almost none inside. Lever now plans to analyze fragments of crust collected from other sites in the Pacific Ocean and the north Atlantic.
“Given the large volume of sub-sea-floor crust, one can’t help but wonder how the amount of living biomass there compares to that at the Earth’s surface,” says Konhauser.
This article is reproduced with permission from the magazine Nature. The article was first published on March 14, 2013.
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15 Comments
Add CommentFor years I have been following research of deep ocean lifeforms.I have yet find any articles about the differences between their DNA and other life on Earth.I can only hope the studies of information of theses crustal organisms are more forthcoming about the DNA data.Is it the oldest life on Earth?
Reply | Report Abuse | Link to this"the researchers found genes from microbes.."
Reply | Report Abuse | Link to thishow is it easier to find microbe genes than to observe the microbes directly?
Very good wrapup on one of the most interesting sub-sets of evolution!
Reply | Report Abuse | Link to thisIf nothing else it will provide future expeditions to other planets with the concept that life could be based on forms other than photosynthesis.
Reply | Report Abuse | Link to thisWhilst I have found the article very interesting, is somewhat disturbing that the author chooses to use the bastardised spelling of "meter" for one of the fundamental units of the Metric system rather than the correct SI definition "metre" which is in almost universal use outside of the United States.
Reply | Report Abuse | Link to thisThe usage of the metric system varies around the world. According to the US Central Intelligence Agency's Factbook (2007), the International System of Units has been adopted as the official system of weights and measures by all nations in the world except for Burma, Liberia and the United States,[56] while NIST has claimed that the United States is the only industrialised country where the metric system is not the official system of units.[57] However, reports published since 2007 hold this is no longer true of Liberia or Burma.
It would be appropriate for an organisation purporting to be scientific to use the generally accepted spelling such a fundamental unit of measure.
There used to be a debate about the source of oil for our planet. This adds another dimension to this debate.
Reply | Report Abuse | Link to thisWas it formed at the beginning of the planet in the original inorganic conglomerate, or from dead dinosaurs, and now, perhaps by primitive bacteria? What is your thought?
The spelling difference between "metre" and "meter" has been mentioned many times before. Can you not simply accept that the United States is different for many reasons that do not need to be discussed here?
Reply | Report Abuse | Link to thiswww.scientificAMERICAN.com
I'm British and weigh 14½ stone and am 1.75 metres tall.
While you are at it, why not get onto those Chinese for writing meter in block letters, or the Indians, Thais, or, especially the Arabs for just using those squigly lines to write meter. I mean, how are you going to know if they spelled it meter or metre? By the way, my spellcheck corrects to meter..Is this really all you have to fuss about?
Reply | Report Abuse | Link to thisThe international standard for Metric system is fundamentally based on the premise of standardised description to avoid transcription errors and uses a decimal base to simplify calculations. It should be noted that the US military makes extensive use of the metric system of measurement to ensure compatibility between allies on the battlefield. However it would appear that the cognitive capabilities of the general population in the US and UK would be overly challenged by converting to the Metric system which is generally in use throughout the rest of the world, including Third World countries.
Reply | Report Abuse | Link to thisArchaic measures such as the foot, gallon client quart stones etc belong in the Middle Ages, and precision in spelling and measurement should be the objective. To avoid ambiguity, the word metre should be used as a unit of measure, and meter as a description of a measuring device.
Spurious references to alternative methods of phonetic spelling in languages other than English cannot be taken seriously (Postman1) outside of an ill informed debating contest. Obviously your spell checker is based on US spelling and if that is your best source of reference then such reference has no place in a relation to a scientific journal discussion.
Actually, the spell check is part of the comments section on SA, which is of course American English. American English is different than the Kings English and from our point of view, more phonetically correct. The word is pronounced me-ter, not me-tre.
Reply | Report Abuse | Link to thisSo you're a bit more than "stoned" in pounds (lbs). Couldn't you have rounded down and said you were 14 stone? At 15+ I would love to be precisely stoned. How many "hands" equate to 1,75 m(une virgule soixante-quinze METRES). Help me out here, "sport of kings" enthusiasts? Oh, sorry I Googled it, "hand" is apparently 4" (four inches) which at (SI) 2.54 cm per inch is 10.16 cm. I leave the necessary act of division for the answer up to anybody interested enough to read this.
Reply | Report Abuse | Link to thisAs if it needs to be even discussed here, we at the Hyphen-Use Association of Not Much To Say would like to point out that without proper hyphenation, phrases like "ill informed debates" are unrecognizable, to say nothing of understandable, without the internationally agreed-upon standardization of, indeed, hyphen use.
Reply | Report Abuse | Link to thisAs we like to say, it's not hyper-legible if it's not hyphen-legible.
This may not be an expert's contribution to this discussion but I feel it is reasonable to mention it.
Reply | Report Abuse | Link to thisIt has been mention that oil is still been produced. May be microorganisms produced all the oil we find in the fields. And they are still producing it. Obviously we need to harness that power. Image we have those microorganism at home and produce all the oil we need for our daily errands. Of course we need clean fuel. We need to understand all this better. We can not afford to go on polluting the atmosphere. We also know (or have heard about)microorganisms making a better job in producing chemicals than the best chemical engineering procedures so far. I do not not to what extent this may be true. It is very interesting this article. [P.S. I did no read all the commentaries about meter or metre. To me it is better meter. But if the British accustom to use metre I do not see there is any problem at all]
Have a nice day!
@string_beery:
Reply | Report Abuse | Link to thisThis was a m etagenomics study. Total DNA from the sample was sequenced and then analyzed for functional content. Since almost all microorganisms can not be cultured this is the best (only?) way to sample the genomes present in the sample.
Isolating and charactering DNA follows standard procedures but there difficulties determining growth condition requirements - bacteria require what they require and that is unknown even for some important human pathogens. A great deal of laborious and time-consuming work (also boring) has to be undertaken in an attempt to elucidate the growth requirements of microbes. Anaerobes are especially difficult to culture and characterise.
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