Thomas Dale Brock (September 10, 1926 – April 4, 2021) was an American microbiologist known for his discovery of hyperthermophiles living in hot springs at Yellowstone National Park.

In the late 1960s, Brock discovered high-temperature bacteria living in the Great Fountain region of Yellowstone, and with his colleague Hudson Freeze, they isolated a sample which they named Thermus aquaticus.

[1] "Life at High Temperatures", a 1967 article summarizing his research, was published in the journal Science and led to the study of extremophiles, organisms that live in extreme environments.

Brock's discoveries led to great progress in biology, contributed to new developments in medicine and agriculture, and helped create the new field of biotechnology.

Though Cleveland was an industrial city, his home was situated near a farm and forested park with views of Lake Erie, so that he grew up in an "idyllic environment", surrounded by nature.

Bill, Brock began attending Ohio State University in 1946, initially with aspirations of becoming a writer, yet still drawn to chemistry and science.

After completing his Ph.D., Brock took a position in the antibiotics research department at the Upjohn Company in Kalamazoo, Michigan, where out of necessity he became self-taught in microbiology and molecular biology.

From a sample of pink bacteria collected from Mushroom Spring, Brock and undergraduate student Hudson Freeze isolated an organism thriving at 70 °C (160 °F) which they named Thermus aquaticus.

[6] Kary Mullis, jointly with Michael Smith, who had invented another essential method of manipulating DNA, was awarded a Nobel Prize[7] in chemistry.

Brock and his wife, Kathie, operated Pleasant Valley Conservancy State Natural Area, a 140-acre (57 ha) preserve in western Dane County, Wisconsin.