A short history of nearly everything - Bill Bryson [151]
In the 1920s two scientists at the University of Chicago, Edson Bastin and Frank Greer, announced that they had isolated from oil wells strains of bacteria that had been living at depths of two thousand feet. The notion was dismissed as fundamentally preposterous—there was nothing to live on at two thousand feet—and for fifty years it was assumed that their samples had been contaminated with surface microbes. We now know that there are a lot of microbes living deep within the Earth, many of which have nothing at all to do with the organic world. They eat rocks or, rather, the stuff that's in rocks—iron, sulfur, manganese, and so on. And they breathe odd things too—iron, chromium, cobalt, even uranium. Such processes may be instrumental in concentrating gold, copper, and other precious metals, and possibly deposits of oil and natural gas. It has even been suggested that their tireless nibblings created the Earth's crust.
Some scientists now think that there could be as much as 100 trillion tons of bacteria living beneath our feet in what are known as subsurface lithoautotrophic microbial ecosystems—SLiME for short. Thomas Gold of Cornell has estimated that if you took all the bacteria out of the Earth's interior and dumped it on the surface, it would cover the planet to a depth of five feet. If the estimates are correct, there could be more life under the Earth than on top of it.
At depth microbes shrink in size and become extremely sluggish. The liveliest of them may divide no more than once a century, some no more than perhaps once in five hundred years. As the Economist has put it: “The key to long life, it seems, is not to do too much.” When things are really tough, bacteria are prepared to shut down all systems and wait for better times. In 1997 scientists successfully activated some anthrax spores that had lain dormant for eighty years in a museum display in Trondheim, Norway. Other microorganisms have leapt back to life after being released from a 118-year-old can of meat and a 166-year-old bottle of beer. In 1996, scientists at the Russian Academy of Science claimed to have revived bacteria frozen in Siberian permafrost for three million years. But the record claim for durability so far is one made by Russell Vreeland and colleagues at West Chester University in Pennsylvania in 2000, when they announced that they had resuscitated 250-million-year-old bacteria called Bacillus permians that had been trapped in salt deposits two thousand feet underground in Carlsbad, New Mexico. If so, this microbe is older than the continents.
The report met with some understandable dubiousness. Many biochemists maintained that over such a span the microbe's components would have become uselessly degraded unless the bacterium roused itself from time to time. However, if the bacterium did stir occasionally there was no plausible internal source of energy that could have lasted so long. The more doubtful scientists suggested that the sample may have been contaminated, if not during its retrieval then perhaps while still buried. In 2001, a team from Tel Aviv University argued that B. permians were almost identical to a strain of modern bacteria, Bacillus marismortui, found in the Dead Sea. Only two of its genetic sequences differed, and then only slightly.
“Are we to believe,” the Israeli researchers wrote, “that in 250 million years B. permians has accumulated the same amount of genetic differences that could be achieved in just 3–7 days in the laboratory?” In reply, Vreeland suggested that “bacteria evolve faster in the lab than they do in the wild.”
Maybe.
It is a remarkable fact that well into the space age, most school textbooks divided the world of the living into just two categories—plant and animal. Microorganisms hardly featured. Amoebas and similar single-celled organisms were treated as proto-animals and algae as proto-plants. Bacteria were usually lumped in with plants,