Going to extremes

Life in the world’s harshest environments could help us tackle climate change, boost food production, develop new drugs and search for extraterrestrial life. Now hundreds of scientists have come together to launch a first vision for research into organisms existing at the extremes Organisms living in the world’s hottest, driest, coldest, darkest and saltiest places are a treasure trove of potential scientific discoveries. These “extremophiles” have evolved unusual ways to survive in Earth’s great deserts, at the poles and in the ocean depths. Some – like single-celled Korarchaeota – live only at very high temperatures, such as in hot springs.  This makes them a test bed for biological theories and a valuable source of chemicals for biotechnology and industry.

Researchers thought extreme environments barely supported life until a few decades ago. But remarkable advances in research methods and access to technology have allowed scientists to uncover many different extremophiles.

Extremophiles have been discovered in geological formations kilometres beneath the Earth’s surface and in sub-glacial lakes, such as giant Lake Vostok, hidden beneath the Antarctic ice sheet. The first clues to life in these isolated environments were reported in the last decade or so.

Decades of exploring, cataloguing and mapping ecosystems in the Earth’s harshest environments still lie ahead. Questions to be answered include: How many hydrothermal vents – fissures spewing life-supporting, mineral-rich boiling water – lie along the 60,000km of undersea mountains on the deep ocean bed? How many lakes lie beneath Antarctica’s ice sheets? Do any extreme environments remain undiscovered?

Scientists must share staff, ideas and equipment to answer these questions. Research in extreme environments remains costly and complex, despite improvements in access to remote locations. To overcome these challenges, more than 200 scientists from 24 countries published the first plan for the future of extreme environment research in January 2011.

The CAREX Roadmap for Research on Life in Extreme Environments identifies future research priorities. It aims to encourage interdisciplinary, international collaboration and attract funding. By teaming up, scientists from different laboratories and specialisms can share costly, scarce equipment designed to withstand – for example – lengthy freezing, boiling and exposure to salt.

CAREX (Coordination Action for Research Activities on life in Extreme Environments), which produced the Roadmap, is the first project to link up European researchers studying life in extreme environments. Since its launch in January 2008, CAREX has prompted researchers from disparate disciplines to find common ground, leading to staff exchanges, access to specialist equipment and new research.

The Roadmap sets out four research themes that tackle fundamental questions and make best use of CAREX researchers. Perhaps the most urgent is examining how life in extreme environments is responding to environment change. All environments are threatened, but the Polar Regions are warming fastest of any area on Earth. We need to test how resilient polar extremophiles are to climate change so we can, perhaps, use them as an early-warning system.

Losing extremophiles could speed up climate change by reducing polar oceans’ capacity to lock away atmospheric carbon dioxide. These oceans are rapidly warming and acidifying, but many polar extremophiles can only survive a narrow temperature range. Some have calcium shells that dissolve in acidic water. Warmer ocean species are already invading polar waters and could replace existing ecosystems with devastating results.

Another research theme is titled life and habitability. Some extreme environments have conditions resembling Mars or Jupiter’s moon Europa.  Europa’s ice-covered ocean is a strong candidate for finding extraterrestrial life. The Roadmap includes plans to find field sites like sub-ice lakes suitable to trial technology for exploring Europa. Scientists will also test theories about the origins of life at field sites picked to resemble the early Earth.

Understanding the limits beyond which life cannot exist is another aim of the life and habitability theme. The Roadmap plans include studying how extremophiles fare extraterrestrially by experimenting on them in low Earth orbit, on the Moon and in outer space.

A third Roadmap theme is looking at how extremophiles respond, adapt and evolve with their environment. Scientists ranging from molecular biologists to ecologists and evolutionary biologists will gain insights into fundamental biological processes.

One pressing question is how proteins and genes work in organisms like the tardigrade, a remarkable gummy bear-shaped invertebrate that can survive desiccation, vacuum and temperatures ranging between -200°C and 151°C. Researchers will use new molecular technologies to screen and compare DNA from the tardigrade and other extremophiles to find genes that make them resistant to freezing, boiling and other stresses.

But scientists want to do more than study extremophiles one at a time. Another research priority is investigating how whole ecosystems thrive at the limits of life. Researchers will watch these communities over several generations. They will also manipulate their environment – exerting stress to see how groups of extremophiles compete, evolve and adapt.

Where do extremophiles live? And do identical organisms exist in similar extreme environments worldwide? These are two questions asked in the Roadmap’s fourth theme. Scientists want to know, for example, whether vent tube worms are confined to Pacific hydrothermal vents. With new technology like RNA/DNA chips, scientists can quickly spot familiar and mystery microbes from pieces of DNA or RNA.

Researchers also want to know what extremophiles do in their habitats. To answer this question, they will study how animals, plants, fungi, bacteria and viruses interact with each other and their environment.

These Roadmap plans have wider benefits than just thrilling basic science discoveries. Biotechnology inspired by extremophiles has already contributed to drug discoveries, and improvements in industrial processes involving textile and leather, paper production and wastewater treatment.

With new technology like RNA/DNA chips, scientists can quickly spot familiar and mystery microbes from pieces of DNA or RNA

A famous example is heat-tolerant Taq polymerase. This enzyme was originally extracted from T. aquaticus, a bacterium discovered in hot springs in Mushroom Pool in Yellowstone National Park in 1966. Using Taq in the polymerase chain reaction (PCR) process revolutionised molecular biology by creating large amounts of nucleic acid for analysis from a tiny sample.

Many other industrial processes using enzymes take place at high temperatures, but most animal enzymes stop working at temperatures above 40°C.  Enzymes extracted from heat-loving extremophiles don’t break down even above 60-70°C. This can make high-temperature processes possible or help companies make energy savings by reducing the heat needed to accelerate chemical reactions.

Other uses of extremophiles include controlling plant pests, extracting mineral ores and cleaning up contaminated sites. Antifreeze proteins extracted from organisms that thrive in the cold have been used to stabilise food and cosmetics. Chemicals extracted from microbes in hypersaline environments have applications in holography and optical computing.

Future research could yield further uses of extremophiles, including ways to manage the effects of climate change. For example, they could produce hydrogen fuel for powering vehicles and generating electricity. Alternatively, they could boost crop production efficiency. Crops could be bioengineered with extremophile characteristics, for example, to withstand water shortages.

The Roadmap is a consensus of around 220 participants from 28 countries mainly developed during four CAREX workshops – two consultation workshops in Spain in 2008, one in Germany in 2009 and a fourth meeting to bring together the findings of previous events in Belgium in 2009.

Working out what research facilities and equipment are needed to make future research plans a reality was a Roadmap aim. The Roadmap recommends improvements in instruments and facilities. Without them, much of this research will be thwarted by the harsh conditions of field sites and the expense of working there.

One major recommendation is to develop more robots for exploring extreme environments.  Robot surveys are more cost-effective and less complex than using human scientists who need housing and feeding.  For marine research, there are already free-roaming robots and others that remain tethered to their mother ship by a cable.

[caption id="attachment_24993" align="alignright" width="200" caption="The tardigrade (Hypsibius dujardini) can survive desiccation, vacuum and a huge temperature range"][/caption]

The Roadmap recommends that the new generation of robotic vehicles communicate better, including providing data to researchers in real-time. Robots and instruments need to work in many different places and be easily upgradable as technology advances. Another challenge is long-term monitoring, which is difficult even in mild climates. The Roadmap makes several recommendations, including ways to test new sensors.

This equipment needs power and many extreme environments, such as hot deserts and the Polar Regions, offer no access to electrical power supplies. Instruments need to survive a long time between visits from scientists because the areas are remote and hard to visit.

Batteries are getting better, but powering vehicles is still a headache for scientific vehicle designers. Developing alternative energy sources like wind and solar energy can be better if several are operated together. This can overcome problems like long periods of winter darkness in Polar Regions and high winds that can damage or destroy wind turbines on instruments.

CAREX was funded until June 2011 under the European Commission Seventh Framework Programme (FP7), but the project doesn’t end there. The first CAREX conference on life in extreme environments was held in Dublin in October 2011. There are plans to establish a Europe-wide research network to study how organisms deal with stress.

Among possible plans for the future are CAREX expanding its research remit to include studies on human survival in extreme conditions and the establishment of trans-national funding for extremophile research. But whatever happens, these are only our first steps on a long journey to the Earth’s extremes.