A better genetic copier
The natural hot springs of Beppu, Japan, are a cauldron of microbial life adapted to extreme heat. These environments, known locally as "jigoku" or "hells," feature pools of boiling water and mud, with temperatures that can exceed 100°C (212°F). Within these superheated waters live thermophilic archaea, single-celled organisms whose cellular machinery can withstand conditions that would destroy life from cooler environments. These microbes contain enzymes—called extremozymes—that are tools in biotechnology.
One discovery from this type of environment is a highly accurate, heat-stable DNA polymerase. This enzyme is the engine of the Polymerase Chain Reaction (PCR), a technique for making billions of copies of a specific DNA sequence. The first mass-marketed PCR enzyme, Taq polymerase, came from a bacterium in Yellowstone's hot springs. Taq polymerase works well at high temperatures but lacks a "proofreading" function, leading to errors during DNA copying. This limitation prompted scientists to search for more accurate enzymes in other geothermal hotspots, including those in Japan.
From microbe to molecule
The search led to the discovery of enzymes like KOD polymerase, derived from the hyperthermophilic archaeon Thermococcus kodakaraensis. This organism was first isolated from a solfatara on Kodakara Island in Kagoshima, an environment similar to Beppu's volcanic vents. T. kodakaraensis thrives at an optimal temperature of 85°C (185°F) but can survive up to 100°C.
Its DNA polymerase possesses a 3'-5' exonuclease activity, which acts as a molecular proofreader. When an incorrect nucleotide is added to a growing DNA strand, this function allows the enzyme to reverse, remove the error, and try again. This proofreading ability makes KOD polymerase significantly more accurate—up to 50 times more faithful—than Taq polymerase. It also works about twice as fast, with an elongation rate of 100-138 nucleotides per second. This combination of speed and accuracy has made KOD and similar high-fidelity enzymes important for applications like genetic cloning, sequencing, and mutagenesis, where the exact DNA sequence is important.