Opposite Extremes


Plenty of scientists consider their instruments to be finicky, liable to produce bogus data at the slightest provocation. But don't tell Craig Cary (pictured left) that instruments are fragile. He uses them everywhere. On field trips to Antarctica, he has spent long days in a tent, doing DNA extractions and analyzing microbial samples, huddled over a portable PCR machine. He has done similar work aboard ships, rocking and swaying high above hydrothermal vents on the ocean floor, when he wasn't in the submersible itself, exploring the steaming depths.

Wherever he goes, the microbiologist brings as much of his lab with him as possible. "My philosophy is a simple one," says Cary, who is director of the University of Delaware's Center for Marine Genomics and also holds an appointment in the department of biological sciences at the New Zealand's University of Waikato. "It's very difficult and expensive to get to these areas, so I'm adamant about making sure to the best of our capability that we're getting what we want. It would be really heartbreaking to spend 18 days doing work in the submersible and get back home to the lab only to find out you screwed up. I've seen it happen a lot."

Underpinning Cary's travels is his interest in the relationship between microorganisms and their environment. "Microbes, unlike most organisms, are very much under the control of their environment--and likewise the other way, they very much mediate their environment," says Cary. "What we're trying to understand in the extreme systems is, what are the environmental drivers that are motivating the composition and structure of the [microbial] community?"

From Shellfish Farms to Hydrothermal Vents

After doing a master's degree at San Diego University specializing in shellfish aquaculture, Cary did a PhD in marine biology at the Scripps Oceanography Institute, also in San Diego. When he started working there in 1983, hydrothermal vents had recently been discovered near the Galapagos Islands and molecular biology had just begun its meteoric rise. Cary took advantage of that confluence of events.

When Cary applied for the program at Scripps, his background with bivalves caught the attention of Horst Felbeck, one of the first to identify endosymbionts (symbiotic microbes that reside within the host cell) in vent clams and mussels. Cary went on to study shallow water bivalves with analogous endosymbiotic relationships. He found that a number of shallow water bivalves had a similar survival strategy -- employing endosymbiotic microbes that oxidize hydrogen sulfide to produce energy.

While at Scripps, Cary coordinated the marine biology seminar series, and invited microbe classification pioneer Stephen Giovannoni from Oregon State University. "I got a chance to meet him and we struck up a friendship," Cary recalls. At the time, NSF had a program to inject molecular biology into the marine sciences by sponsoring ten postdocs a year. When he finished his PhD, Cary applied for and received an NSF post-doctoral fellowship with Giovannoni in mind.

Cary had done very little molecular work before then because the field was so new. "I was fortunate to get in there when everything was as new to [Giovannoni] as it was to me. It just catapulted me into the field," Cary says. With Giovannoni, Cary tracked the inheritance of endosymbiotic bacteria in the progeny of the clams and other vent animals.

Following his postdoc, Cary accepted a position at the University of Delaware. Much of the work there has focused on the Pompeii worm, which builds a protective polysaccharide tube in the hottest part of the vent, making it a leading candidate for the most heat-tolerant animal on the planet. The temperature of its workaday environment ranges between 50 and 65 degrees Celsius, and occasional bursts from the vent will subject the worm to a scalding 90 degrees C and above. "It puts itself in harm's way," says Cary.

To study the animal, Cary goes on cruises to hydrothermal vents like the one located in the Pacific Ocean's Mid-Oceanic Ridge, about 1,200 miles off the coast of Costa Rica. The surface ship may stay in the area for two weeks or more, while Cary and colleagues take daily trips in the submersible to collect samples.

Cary studies the symbiotic relationship between the worm and bacteria that live in a mucus membrane on its back, which it points towards the vent opening. The filamentous bacteria combine with the mucus to form a hair-like surface that apparently shields the Pompeii worm from physical and thermal bombardment by the vent.

Once that is done, Cary and his colleague Alison Murray at the Desert Research Institute in Reno, Nevada, plan to test samples against microarrays to determine a 'core metabolism' shared by all members of the community. This should yield clues about the environmental factors that shape the population and help decipher the symbiotic relationship between the worm and the bacteria.

Cary's field research involves collecting samples and analyzing them for messenger RNA (mRNA), which is synthesized in preparation for protein synthesis, providing a snapshot of the proteins that an organism is producing. Doing the analysis in a traditional laboratory setting is out of the question. By then, "the mRNA transcript pool has completely changed. What you're assessing at the surface is nothing like at the bottom," says Cary.

Cary and his team developed an in situ preservation tool that inhibits the enzymes that destroy mRNA, killing the organism and chemically 'freezing' the mRNA to preserve it for later analysis. To ensure that the first experiments worked properly, they brought instruments aboard the surface ship that the submersible returns to every day, where they could assess the quality of the mRNA transcripts. If more transcripts needed to be collected, it would be much easier to do it on the next day's run than to return the following season. "It gives us a sort of quality control," says Cary.

Opposite Extremes

To better understand microbial adaptations, Cary recently began working at the other extreme: the cold, dry valleys of Antarctica. "We want to see whether hypotheses that we consider in high-temperature environments also pertain to low-temperature environments," he says.

Cary and his colleagues were surprised by the diversity of the microbial community they found. "It's way more diverse than we would have predicted based on the simplicity of the system. In a system that is carbon limited and extremely sparse biologically, why is the diversity so high?"

Working in extreme environments has plenty of rewards, Cary says. By definition, not many people are working in extreme locales. "When a student can ask a fundamental question and find out that we don't know the answer, there's a possibility of doing some really exciting science."

But where there are opportunities, there are also challenges. Conducting science is more challenging in remote, inhospitable places. Cary warns anyone interested in studying extreme environments that the pace of discovery is slower. "I don't know how many times we've had to reconstruct and modify and adapt equipment to get it right," he says. But the rewards are worth the effort. "Everything you achieve is new. The rewards are far greater."

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