and head of the department, and nine years later he
was appointed director of the Institute of Microbiology.
He retired in 1958.
Waksman brought medicine from the soil. By
studying soil-based acintomycetes, he was able to
extract a number of antibiotics such as actinomycin
(1940), clavacin, streptothricin (1942), streptomycin
(1943), grisein (1946), neomycin (1948), fradicin, can-
dicidin, candidin, and more. His discovery of strepto-
mycin, which was the first effective treatment against
tuberculosis, brought him the 1952 Nobel Prize in
physiology or medicine.
He published more than 400 scientific papers and
has written, alone or with others, 18 books, including
Principles of Soil Microbiology(1927) and My Life
with the Microbes(1954), an autobiography. He was a
member of numerous scientific organizations. In 1950
he was made commander of the French Légion d’Hon-
neur, and in 1952 was voted as one of the most out-
standing 100 people in the world today. He died on
August 16, 1973, in Hyannis, Massachusetts.
Wallace’s line An imaginary line drawn by A. R.
Wallace that passes between the Philippines and the
Moluccas in the north and between Sulawesi and Bor-
neo and between Lombok and Bali in the south (the
Mariana Trench). It separates the Oriental and Aus-
tralian biogeographical regions. It marks the limits of
distribution for many major animal groups that appear
on one side of the line but are absent on the other side.
Warburg, Otto Heinrich(1883–1970) GermanBio-
chemist Otto Heinrich Warburg was born on October
8, 1883, in Freiburg, Baden, to physicist Emil Warburg.
He studied chemistry under Emil Fischer and received
his doctor of chemistry from the University of Berlin in
1906, and a doctor of medicine from the University of
Heidelberg in 1911.
In 1918 he was appointed professor at the Kaiser
Wilhelm Institute for Biology, Berlin-Dahlem, and from
1931 to 1953 he was director of the Kaiser Wilhelm
Institute for Cell Physiology (now Max Planck Insti-
tute) in Berlin.
He specialized in the investigation of metabolism in
tumors and respiration of cells. He discovered that
flavins and the nicotinamide were the active groups of
the hydrogen-transferring enzymes, and early discovery
of iron–oxygenase provided details of oxidation and
reduction (redux reactions) in the living organisms. For
his discovery of the nature and mode of action of the
respiratory enzymes that enable cells to process oxy-
gen, he was awarded the Nobel Prize in 1931. He was
offered a second Nobel Prize in 1944 for his enzyme
work, but he was not allowed to accept it, since he was
living under the Hitler regime. He later discovered how
the conversion of light energy to chemical energy is
activated in photosynthesis. During the 1930s he
showed the carcinogenic nature of food additives and
cigarette smoke and demonstrated how cancer cells are
destroyed by radiation.
Warburg is the author of New Methods of Cell
Physiology(1962). He died on August 1, 1970.warm-blooded Refers to organisms that main-
tain a constant body temperature. Also known as
HOMEOTHERMIC.water potential Direction of water flow based on
solute concentration and pressure. An example is
osmosis, which is the diffusion of water across a
semipermeable barrier, such as a cell membrane, from
high water potential to lower water potential.
Also a measure of the moisture stress in plants or
soil, measured in megapascals. A more negative value
indicates greater moisture stress. Soils with no moisture
stress have a water potential of 0 to –1 mPa. The mea-
surement of soil water potential involves the use of sen-
sors that determine the energy status of the water in
soil. The energy state describes the force that holds the
water in the soil. Two methods of measuring soil water
potential are the heat dissipation method or the electri-
cal resistance method.water table The level below the earth’s surface at
which the ground becomes saturated with water; usual-
ly mimics the surface contour and is set where hydro-
static pressure equals atmospheric pressure.water vascular system An internally closed network
of watery canals in echinoderms (e.g., starfish, sand346 Wallace’s line