Science & Technology: There's Life on the Edge ; Tiny Organisms Exist in the Most Extreme Environments, and They May Help Us Generate Power and Clean Up Pollution. Simon Hadlington Reports

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In Phillip Wright's laboratory, there is a large silver cabinet resembling a fashionable fridge. Inside, rows of fluorescent light tubes shine down on ranks of conical flasks containing a bright green, murky fluid. It looks like something Fungus the Bogeyman might enjoy for supper. In fact, this green soup could one day be at the forefront of a new energy economy. Feed it industrial waste, and it can produce hydrogen.

The flasks contain cultures of an organism called a cyanobacterium. It was isolated from a lake in Libya with an exceptionally high concentration of salt. Most organisms would simply pickle in such a powerful brine. This one thrives.

This cyanobacterium is an example of an "extremophile", an organism that is capable of surviving on the margins of what is biologically feasible. Micro-organisms can be found living in sub- zero conditions in Antarctic lakes, or in hot vents in the seabed, under huge pressures and in temperatures exceeding 100C. They can be found in arid, parched regions of the Sahara desert - and, like Professor Wright's cyanobacterium, in lakes where the water is saturated with salt.

Wright, of the Department of Chemical and Process Engineering at the University of Sheffield, wants to find out if the unusual properties of extremophiles can be harnessed for a range of useful purposes, from cleaning up pollution and generating fuels to producing new drugs.

The cyanobacterium, called Euhalothece, was isolated from salt lakes on the fringes of the Sahara. In these lakes, the concentration of salt is many times that found in sea water.

These cyanobacteria contain chlorophyll - the same green pigment that other plants use to produce food from the energy of the Sun. However, a by-product of their growth is hydrogen. "We have found that as well as being tolerant of very high concentrations of salt, these organisms can also grow in high levels of other chemicals, such as oil and other substances that are often present in contaminated sites," Wright says. "So we are looking at whether it is possible to take waste material and feed it to cultures of this type of organism to produce hydrogen gas, a commercially useful by- product. Can we make hydrogen from such a system on an industrial scale? This is potentially very attractive - the main input is sunlight, but we get something useful out of it."

Across the room from the cabinet, Wright slides up the glass panel of a fume cupboard to reveal a gently steaming water-bath. Submerged in the water are half a dozen glass flasks, long necks protruding above the surface.

The flasks contain cultures of an organism called Sulfolobus, growing happily on a diet of concentrated alcohol and salt at a temperature of 80C. "These microbes live naturally in hot springs, and this particular batch was isolated from hot sulphurous pools around the Bay of Naples," Wright says. "We are testing them to see how they grow on a range of different alcohols of increasing concentration. They can also grow in pretty acidic conditions."

In the chemical and pharmaceutical industries, many processes take place at high temperatures and in solvents such as alcohols and ketones (acetone, often used as nail-polish remover, is a ketone). Most micro-organisms cannot tolerate such heat, and prefer to grow in water-based environments. This makes it difficult to integrate microbes into many processes - even though they can carry out important chemical reactions very efficiently. Microbes that can withstand heat - "thermophiles" or "hyperthermophiles" - could be useful in these circumstances.

"There is also the issue of infection by other bugs," Wright says. "By carrying out fermentations at high temperatures and in concentrated solvents such as alcohol, you effectively have a selectively sterile environment. This could be important for the production of pharmaceuticals or in the food processing industry. …