Waking up ancient life Scientists are discovering microbes that are millions of years old, says Bernar d Dixon

The truly modern microbe is one that has been selected from a population of billions, or designed by genetic engineering, to direct some sophisticated money-making process for the biotechnology industry. By the same token, the microbe of yesteryear seemsrather a dull fellow - its activities unrecorded, its praises unsung, its DNA unmodified.

Now the day of the ancient microbe may be at hand. That is certainly the view of Max Kennedy and colleagues at the New Zealand Institute for Industrial Research and Development in Lower Hutt, New Zealand. They believe that bacteria and other microbes recovered and rejuvenated after millions of years could generate valuable substances that are not produced by their present-day descendants. The ancient microbe may also teach us a good deal about evolution. But rejuvenation could cause unpredictable hazards, too.

Writing in the journal Microbiology, the New Zealanders bring together information from disparate sources to establish that long-lost microbes really can be recovered and cultured. While this idea itself is hardly novel, it has in the past been envelopedin uncertainty, controversy and even ridicule.

Decades ago, claims for the revival of bacteria from rocks hundreds of millions of years old attracted particular scepticism. The reason was the lack of similar evidence to bridge the enormous gap between those claims and modern examples of microbes remaining viable for much more modest periods of 10 or 20 years. If long-term survival was a reality, critics argued, one would expect to find intermediate instances, too.

Another ground for suspicion was the possibility that organisms, apparently disinterred after aeons of time in "suspended animation" were really present-day microbes which investigators introduced unwittingly into their specimens during the course of their work. Judging from the details given in their reports, some of the investigators do not seem to have taken adequate precautions to prevent such contamination.

Max Kennedy and his collaborators believe, in addition, that the sceptical aura surrounding work of this sort has discouraged some microbiologists from describing their bounty in the scientific literature. Nevertheless, they have now trawled through the world's scientific journals, and other sources, and created an impressive database containing some 5,000 microbes recovered from 62 different sites by 37 The Independent research teams.

The finds range from Bacillus circulan bacteria from 650-million-year-old rocks in Irkutsk in Russia to the anthrax bacillus (B. anthracis) that was still viable on the Scottish island of Gruinard 40 years after being released there during Second World War biological warfare experiments by the British government.

The claims in the database do not all carry equal conviction and an inexplicable gap remains between 100,000 and 1 million years. But the overall evidence for the recovery and cultivation of ancient microbes is impressive. Some of the most striking examples come from the US Department of Energy's Deep Microbiology Sub-program, with finds going back to 200-million-year-old Triassic sediments from beneath the state of Virginia.

British discoveries include bacteria from 600-million-year-old soil in Harlech, Wales, and from 195- to 225-million-year-old rock salt mined by ICI in Winsford, Cheshire.

The New Zealand researchers warn of the possibility that some of the microbes isolated from rocks may have been carried there by water seeping into porous structures. However, they conclude that "the collection of the data is so large and made by so manyThe Independent teams that it is now possible to say that revivals from ancient specimens is a reality".

Little research has been conducted into the potential uses of such venerable micro-organisms. But the principle behind doing so is shown by the initiative of Keith Thomas of Brewlab at the University of Sunderland. He has recreated porter ale using a yeast from a bottle of the same beer recovered from a sailing barge that sank off Littehampton in 1825. With an 1850 recipe and the appropriate barley, Thomas produced the original ale. It is now being manufactured on a modest commercial scale.

More intriguing is the prospect of harnessing ancient microbes to manufacture chemicals not found in microbial or other living cells today. Given that bacteria exchange genes by a variety of mechanisms and can evolve extremely rapidly, it is possible that those unearthed from the distant past have synthetic capacities that have been lost in the course of evolution.

Antibiotics such as penicillin are typical products of present-day bacteria. There are thus good prospects of finding others not known to modern science. Likewise, ancient microbes may be capable of making different types of drugs and other substances. One candidate, already identified through the US Deep Microbiology Sub-program, is an unusual pigment that could be used in the food, cosmetic and textile industries.

Max Kennedy and his colleagues point out potential dangers in the disinterring of long-preserved organisms that are genetically different from their present-day counterparts. One is the capacity of an ancient microbe to cause a disease against which our natural defences may have waned.

The New Zealanders suggest scientists investigating such organisms would be prudent to adopt the same precautions as when working with genetically engineered bacteria and viruses. There are strict containment procedures to prevent such microbes from infecting laboratory staff or escaping into the environment. Ancient microbes may have to be treated with comparable caution.