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Life in the Deep

Recent Discoveries & Highlights

Some of the latest scientific news about deep-sea animals and microbes.

Important but elusive microbes grown in lab for first time ever

Black and white electron micrograph of microbe, showing two protruberances like devil's horns. Image courtesy of Terry Beveridge

To thrive, we humans need oxygen, and temperatures below about 40°C (104°F). Remove the oxygen or increase the temperature, and we don't survive long. But at the bottom of the ocean, some creatures actually prefer hot, low oxygen environments. Around deep-sea hydrothermal vents, temperatures often exceed 50°C (122°F). Fluids emitted by vents can also be acidic (pH 4.5 or less) and oxygen-poor.

Despite these challenging conditions, many kinds of microbes grow on and in the rocks and mineral deposits around vents. But scientists only know about most deep-sea microbes by examining genetic material found in rock or vent fluid samples: up to now, it has proven impossible to grow most of these tiny creatures in the lab. So we don't know what they look like, how they cope with their environment, or how they interact with other species.

Now a team of researchers led by Anna Louise Reysenbach of Portland State University (OR) has managed to culture a type of microbe whose genetic material has previously been detected in a variety of samples.

The researchers collected sulfide deposits from vents in the East Pacific and South Pacific, and scraped off the iron- or sulfur- rich surface layers. They then incubated some of these scrapings at 70°C (158°F), while experimentally varying the pH, potential sources of nutrients and other conditions. They hit on a combination that some of the microbes liked, and for the first time ever, were able to get them to survive and reproduce in the lab. The researchers are now looking forward to investigating how these microbes cope with environments that would kill most terrestrial forms of life.

» More: a photostory about their discoveries, which are published in the journal Nature

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Invasion of the body shapers

Adult tubeworms, Riftia sp. Image courtesy of Monika Bright

In some ways, an adult tubeworm (left) is more like a plant than an animal. It spends its life anchored in one spot, and it has no mouth or gut. Instead, it contains a specialized organ (the trophosome) packed full of a particular type of microbe. The tubeworm takes up chemicals from the environment and supplies them to its microbes; in return, the microbes use the chemicals to manufacture food for themselves and for their tubeworm host.

Adult tubeworms would not survive without their microbes. But newly-hatched tubeworms (larvae) contain neither microbes nor the tissues to house them: they need to acquire them somehow. Now researchers have discovered new evidence for how tubeworms and microbes team up.

Shortly after a tubeworm larva settles in an appropriate habitat (one containing the right mix of chemicals), microbes living in the environment begin to invade the tubeworm's skin in much the same way that pathogenic bacteria infect a host. After the right type of microbes have migrated to the part of the body where the trophosome develops, the juvenile tubeworm destroys any microbes remaining in its skin and muscles, and fresh infections by other microbes cease.

This research overturns previous theories about how tubeworms acquire symbiotic microbes and develop trophosomes. The research is published in a May 2006 issue of the journal Nature.

» More: a press release about this discovery

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In hot water

Thermo-tolerant sulfide worms (P. sulfincola), with star-shaped gills protruding from their tubes, at the base of a hydrothermal vent chimney. The white background is a microbial mat. Photographed at the Cleft hydrothermal field, off the coast of Oregon, 2200m below sea level. Courtesy of W. Chadwick/National Undersea Research Program and Monterey Bay Aquarium Research Institute

If you had a bath in water at 49°C (120°F), you could get third-degree burns in just five minutes. But one type of deep-sea creature finds this temperature fine. Alvinellid worms (left) live near hydrothermal vents in the Pacific Ocean. Here, hot fluid jets out of the seafloor at temperatures up to 350°C (660°F), but cools rapidly when it meets the overlying seawater, which is near freezing. In this dynamic environment, it can be difficult to measure exactly what temperatures animals living near vents experience. So Peter Girguis from Harvard and Raymond Lee from Washington State University tried investigating the question using worms (species Paralvinella sulfincola) in high-tech aquaria in the lab. When offered a range of temperatures to choose from, the test worms moved to areas heated at 40-50°C and stayed there for several hours. In a recent paper in the journal Science, the researchers suggest that the ability to survive these temperatures may enable the worms to exploit the lush mats of bacteria growing in conditions that other animals cannot tolerate.

» More: a press release about these findings

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"Yeti crab" discovered

Bob Vrijenhoek

Scientists on an expedition to the South Pacific, led by Dr Robert Vrijenhoek of the Monterey Bay Aquarium Research Institute (left), recently discovered a new species of crab living near hydrothermal vents more than 2000 meters below the ocean surface.

A distant relative of the hermit crabs found in tide pools, the deep-sea crab is white and about 15cm (6 inches) long. Strikingly, its limbs are covered in fine, pale yellow, hair-like spines (called setae). This apparent "hairiness" is reflected in the scientific name bestowed on the new species (Kiwa hirsuta — "hirsute" means "hairy"), and led to its nickname: the Yeti crab.

» More: a press release about the Yeti crab

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