Thermus aquaticus is a thermophilic gram-negative bacterium that has played a key role in the modern revolution in genetic research, genetic engineering, and biotechnology (see below). Thermophilic bacteria are bacteria that thrive at very high temperatures, often above 45° C (113° F). Thermus aquaticus was originally isolated from a number of hot springs in Yellowstone National Park and a hot spring in California (U.S.A.) and was subsequently isolated from hot springs in other parts of the world and even from artificial hot water environments such as hot tap water (Brock and Freeze 1969; Brock and Boylen 1973). Previously, microbiologists had enriched for thermophilic bacteria at 55° C, but the discoverer of T. aquaticus, Thomas Brock, found that many thermophiles in his studies of microbial ecology would not be easily detected at such a "low" temperature since they require temperatures above 70° C to flourish. As Brock has noted, his discovery provides an excellent illustration of the often unpredictable value (both academic and applied) of basic research (Brock 1997).

In the 1980s, a method known as the polymerase chain reaction (PCR) was developed to generate many copies of targeted segments of DNA from very tiny samples (Mullis and Faloona 1987; Arnheim and Erlich 1992; visit this site for a visual explanation of the principle of PCR) . This technique includes repeated cycles of melting apart of the two strands of each double-stranded DNA molecule (typically at 92° to 95° C) alternating with the extension of new complementary strands to create additional copies. To be practical, this method requires the use of a DNA polymerase that is not destroyed by this heating (DNA polymerases are enzymes that play a key role in DNA synthesis within cells; see Pavlov et al. 2004 for an overview of DNA polymerases). Fortunately, evolution has provided such polymerases in bacteria adapted to live at very high temperatures (e.g., in hot springs). Chien et al. (1976) had already purified a stable DNA polymerase from T. aquaticus with a temperature optimum of 80° C, which proved to serve very well for the automation of PCR. The use of DNA polymerases from T. aquaticus and other thermophiles in PCR and related applications, such as DNA sequencing, has revolutionized biotechnology. The humble T. aquaticus enormously expanded what questions could be practically addressed in fields ranging from biomedical science ("what is the genetic basis for disease X and does this patient have this disorder?") to animal behavior ("were all the young in this bluebird nest actually sired by the mother's apparent mate?") to conservation ("is this whale meat being sold truly from the species the seller claims?") to forensics ("can this accused criminal possibly have left the DNA evidence found at the crime scene?") and beyond.