American Scientist

Dark Life: Martian Nanobacteria, Rock-Eating Cave Bugs, and Other Extreme Organisms of Inner Earth and Outer Space. Michael Ray Taylor. 304 pp. Scribner, 1999. $23.

Michael Ray Taylor is a journalism professor and an avid spelunker who takes us on an adventure in microbiology. He starts by collecting samples from caves for microbiologists, which leads to an interest in travertine, a carbonate mineral found in caves. Bacteria seem to be involved in some of the formations. Some of these organisms are nanobacteria, a tenth the size of more familiar bacteria. Besides a recent paper that implicates a nanobacterium in gall stone formation and a few fragmentary reports on the Web, there isn't much on nanobacteria in the professional literature.

Next Taylor tells us about chemoautotrophic bacteria (normal size), also involved in cave formations. These bacteria oxidize elemental sulfur to sulfate, to form sulfuric acid. The acid dissolves carbonate rock. (In carbonate rock, a little bit of acid goes a long way. Stalagmites and stalactites get made by carbonate dissolved by the acid going drip, drip, drip.)

Taylor asks whether there could there be life on Mars. Geologic evidence indicates that Mars once had a great deal of water flowing over it. It once had an atmosphere and a much warmer climate. Life could have evolved on Mars as it did on our planet. Chemoautotrophic bacteria may be growing near warm geothermal zones far under the surface of Mars. Cornell researchers have unearthed chemoautotrophic bacteria at the bottom of a 7,000-foot, aseptic well. Scientists in Washington state have recovered chemoautotrophic bacteria growing in basalt. Around geothermal vents in the ocean, chemoautotrophic bacteria grow abundantly. Clams and worms have evolved to consume these bacteria. This suggests there could have been some very sophisticated life on Mars.

Taylor introduces us to a student with a NASA internship to carry out some sophisticated electron microscopy of meteorites thought to be from Mars. She finds what appear to be fossils of bacteria. Taylor describes the adventures of this intern, the people who try to suppress her work and those who agree with her findings and have their own evidence to contribute. And the author cites people who scoff at the work, pointing out that electron microscopy is a superb way to generate artifacts. A consensus on this work has yet to emerge. This provides an interesting view of the politics of science.

The discussion of bacteria surviving in difficult environments introduces the Archaea, the third kingdom. These bacteria, very different from familiar eubacteria, have been known for only 20 years. The author discusses scientists who work with these bacteria. Much of this work is hampered because many of the bacteria can't grow in a laboratory. They must be studied in situ, and we find microbiologists working around geothermal vents in tiny submarines like Alvin.

This is a fine book. The reader confronts a new idea on each page. It is unlike scientific prose, written in a stream-of-consciousness style. Some of the facts aren't quite right. The story about sequencing 16s ribosomal RNA is a little distorted. The account of using polymerase chain reaction to amplify small amounts of DNA isn't precise. Some familiar figures in microbiology aren't quite as they are portrayed. Not precise science but a superb adventure through all sorts of exciting new concepts in microbiology.—James L. Botsford, Biology, New Mexico State University