Microbiology and Immunology

Brock, Thomas D. WORLD OF MICROBIOLOGY AND IMMUNOLOGY

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BBrock, Thomas D.ROCK, THOMASD.(1926- )

American bacteriologist

Thomas D. Brock was born in Cleveland, Ohio, and has lived

in the midwestern states of the United States all his life.

Brock’s 1967 summary article in Science,entitled “Life at

High Temperatures” generated a great deal of interest, and

spawned the branch of microbiology concerned with bacteria

that live in extreme environments.

After graduating from high school in Chillicothe, Ohio,

Brock enlisted in the Navy. As a veteran, he enrolled at Ohio

State University in 1946. He graduated with a degree in

botany in 1949, a MS degree and a Ph.D. in 1952. After grad-

uation he joined the antibioticsresearch department at the

Upjohn Company. His relative lack of microbiology training

to that point necessitated that he learn on the job. This embrac-

ing of new aspects of research continued throughout his

microbiology career. Leaving Upjohn after five years, he

accepted a position at Western Reserve University (now Case

Western University). In 1960 he moved to Indiana University

as an Assistant Professor of Bacteriology. He remained there

until 1971.

In 1963, Brock had the opportunity to pursue marine

microbiologyresearch at the Friday Harbor Laboratories of the

University of Washington. There he studied Leucothrix mucor.

His diagrams of the twisted configurations called “knots”

formed by the growing organisms became a cover story in

Scienceand were featured in the New York Times.This work

also stimulated his interest in the microbial ecology of sulfur

springs, which led him to conduct research at Yellowstone

National Park over the next decade.

Beginning in the mid 1960s, Brock began field research

in Yellowstone National Park, Montana. At the time of these

studies, bacterial life was not thought to be possible at growth

temperatures above about 80° C. Brock found microorgan-

ismsthat were capable of growth and division at temperatures

of nearly 100° C, the temperature at which water boils.

In particular, Brock isolated and named the bacterium

Thermus aquaticus. This microbe was the first so-called

archaebacteria to be discovered. Archaebacteria are now

known to be a very ancient form of life, and may even consti-

tute a separate kingdom of life. The discovery of Thermus

aquaticusis thus, one of the fundamental milestones of micro-

biology.

Brock’s discovery has also had a significant impact in

the field of biotechnology. The enzymesof the bacterium are

designed to work at high temperatures. In particular, a poly-

merase is the basis of the polymerase chain reactionthat is

used to artificially amplify the amount of deoxyribonucleic

acid. The use of PCRhas spawned a multi-billion dollar

biotechnology industry.

In 1971, Brock moved to the Department of

Bacteriology at the University of Wisconsin-Madison. He is

currently E.B. Fred Professor of Natural Sciences-Emeritus at

Wisconsin.

Brock has also been a prolific writer and scientific his-

torian. His numerous books include volumes on the biology of

microorganisms, the principles of microbial ecology, the mile-

stones in microbiology, and a profile of Robert Koch. In the

1980s, he formed his own scientific publishing company,

which continues to the present day.

For his groundbreaking research and publishing efforts,

Brock has received many scientific achievement and educa-

tion awards in the United States and worldwide.

See alsoExtremophiles; Tag enzyme

BROTH•seeGROWTH AND GROWTH MEDIA

BROWNIAN MOTION• seeBACTERIAL MOVEMENT

BBrucellosisRUCELLOSIS

Brucellosis is a disease caused by bacteriain the genus

Brucella. The disease infects animals such as swine, cattle,

and sheep; humans can become infected indirectly through

contact with infected animals or by drinking Brucella-contam-

inated milk. In the United States, most domestic animals are

vaccinated against the bacteria, but brucellosis remains a risk

with imported animal products.

Brucella are rod-shaped bacteria that lack a capsule

around their cell membranes. Unlike most bacteria, Brucella

cause infection by actually entering host cells. As the bacteria

cross the host cell membrane, they are engulfed by host cell

vacuoles called phagosomes. The presence of Brucella within

host cell phagosomes initiates a characteristic immune

response, in which infected cells begin to stick together and

form aggregations called granulomas.

Three species of Brucella cause brucellosis in humans:

Brucella melitensis,which infects goats; B. abortis,which

infects cattle and, if the animal is pregnant, causes the sponta-

neous abortion of the fetus; and B. suis,which infects pigs. In

animals, brucellosis is a self-limiting disease, and usually no

treatment is necessary for the resolution of the disease.

However, for a period of time from a few days to several

weeks, infected animals may continue to excrete brucella into

their urine and milk. Under warm, moist conditions, the bac-

teria may survive for months in soil, milk, and even seawater.

Because the bacteria are so hardy, humans may become

infected with Brucella by direct contact with the bacteria.

Handling or cleaning up after infected animals may put a per-

son in contact with the bacteria. Brucella are extremely effi-

cient in crossing the human skin barrier through cuts or breaks

in the skin.

The incubation period of Brucella, the time from expo-

sure to the bacteria to the start of symptoms, is typically about

three weeks. The primary complaints are weakness and

fatigue. An infected person may also experience muscle aches,

fever, and chills.

The course of the disease reflects the location of the

Brucella bacteria within the human host. Soon after the

Brucella are introduced into the bloodstream, the bacteria seek

out the nearest lymph nodes and invade the lymph node cells.

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