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> Oceans-the surprising cradle of a lot more life than expected
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post Aug 02, 2006, 11:28 PM
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A single gulp of ocean water can contain more than 20,000 different types of bacteria and microbes, according to a recent investigation made by scientists.

"Microbes constitute the vast majority of marine biomass and are the primary engines of Earth's biosphere," said Dr Sogin, from the Marine Biological Laboratory's (MBL) Josephine Bay Paul Center for Comparative and Molecular Biology and Evolution, located in Woods Hole, Massachusetts, US.

The findings suggest that microbial biodiversity is by far greater than previously anticipated, according to Mitchell Sogin, of the US Marine Biological Laboratory in Woods Hole, Massachusetts, and colleagues.

The study conducted by prestigious scientists has been published in the Proceedings of the National Academy of Sciences and is part of the Census of Marine Life (CoML).

The method used to identify new “fragments” of life consists of gathering tiny probes of DNA (DNA snippets) and rapidly distinguish them. It is called "454 tag sequencing" and its tremendous advantage is that thousands of such tests can be conducted at the same time.

Other conclusions of the study published in the Proceedings of the National Academy of Sciences are referring to the fact that the species of microbes found in the sea water could be 10 to 100 times more abundant and that their role in the ecosystem is not yet fully understood, since many of these species are scarce and have a restraint living territory.

"This study shows we have barely scratched the surface. Over the last 10 to 20 years molecular studies have shown there to be more than 500,000 kinds of micro-organisms," Mitchell Sogin said.

"In our new study, we discovered more than 20,000 in a single litre of seawater, having expected just 1,000 to 3,000. These observations blow away all previous estimates of bacterial diversity in the ocean," he added.

"The number of different kinds of bacteria in the oceans could eclipse five million to 10 million."

"Just as scientists have discovered through ever more powerful telescopes that stars number in the billions, we are learning through DNA technologies that the number of marine organisms invisible to the eye exceeds all expectations, and their diversity is much greater than we could have imagined."

According to Sogin, microbes’ activity is vital in Earth’s evolution, since they are the oldest life forms, and they can also offer a new perspective on this evolution.

The project conducted by Sogin involves 1,700 scientists from 73 countries and aims to create a comprehensive and authoritative portrait of life in the oceans in the past, present and future. Its ambitious purpose is to become a 10-year initiative to catalogue the rich diversity of the oceans before it is depleted.

The next objective for scientists is to fully understand how many species of micro- organisms evolved and survived, and what effect they might have on the environment.

"Microbes constitute the vast majority of marine biomass and are the primary engines of the Earth's biosphere. They are the oldest life forms, the primary catalysts of energy transformation, and fundamental to the biogeochemical cycles that shape our planetary atmosphere and environment," Dr Sogin said.

Scientists took seawater samples from several sites around the world, including a hydrothermal vent on an underwater volcano in the Pacific Ocean. Sorgin and his colleagues from the U.S., the Netherlands and Spain did a genetic analysis of eight samples of water taken from different sites in the Atlantic and the Pacific, from depths ranging from 550 to 4,100 metres.

"This implies there is a whole world of unexplored habitat that oceanographers are only just becoming aware of," he added.

The role of these microbes is to break down organic material, and transform it into nutrients for other organisms. They pose no harm to human beings.

Ocean bacteria are invisible to the naked eye, but can be strangely beautiful under a microscope, shaped like macaroni or beads of pearls.

"Peering through a laboratory microscope into a drop of seawater is like looking at the stars on a clear night," said Victor Gallardo, vice chair of the CoML.

"The 454 tag sequencing strategy increases resolution like the Hubble Telescope. We can see marine microbial diversity to which we were blind before." A "rare biosphere" is how the scientists described these low-abundance background populations.

"We know there will be major ecological changes on our planet. The microbial world has to survive the changes and one way is to have a lot of novelty in your genome so that you can cope with different environmental conditions," explained Dr Sogin.

"These rare, ancient organisms are likely to prove a key part of nature's history and strategy," explained Dr Gallardo.

"The major photosynthesis in the ocean is carried by the microbial life forms, and that is the major input in terms of capture of energy from the Sun," explained Dr Sogin. "The microbes are a major input into climate parameters."
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