Watson, James D. WORLD OF MICROBIOLOGY AND IMMUNOLOGY594•
has proved to be challenging, as both Giardia and
Cryptosporidiumform dormant and chemically resistant struc-
tures called cysts during their life cycles. The cyst forms are
resistant to the killing action of chlorine and can pass through
the filters typically used in water treatment plants.
Contamination of the water supply of Milwaukee, Wisconsin
with Cryptosporidiumin 1993 sickened over 400,000 people
and the deaths of at least 47 people were subsequently attrib-
uted to the contamination.
Water quality testing often involves the use of a test that
measures the turbidity of the water. Turbidity gives an indica-
tion of the amount of particulate material in the water. If the
water is contaminated with particles as small as bacteria and
viruses, the turbidity of the water will increase. Thus, the tur-
bidity test can be a quick means of assessing if water quality
is deteriorating and whether further action should be taken to
enhance the quality of the water supply.
Water quality is also addressed in many countries by
regulations that require the sampling and testing of drinking
water for microorganisms. Testing is typically for an “indica-
tor” of fecal pollution of the water. Escherichia coliis often
the most suitable indicator organism. The bacterium is present
in the intestinal tract in greater numbers than the disease-caus-
ing bacteria and viruses. Thus, the chances of detecting the
indicator organism is better than detecting the actual pathogen.
Additionally, the indicator does not usually multiply in the
water (except in tropical countries), so its presence is indica-
tive of recent fecal pollution. Finally, Escherichia colican be
detected using tests that are inexpensive and easy to perform.
Because the prevention of water borne disease rests on
the adequate treatment of the water, underdeveloped regions
of the world continue to experience the majority of water
borne diseases. For example, in India the prevalence of
cholera is so great that the disease is considered to be epi-
demic. But, as exemplified by communities like Walkerton
and Milwaukee, even developed countries having an extensive
water treatment infrastructure can experience problems if the
treatment barriers are breached by the microorganisms.See alsoBacteria and bacterial infection; Bioremediation;
Epidemics and pandemics; Water purificationWWatson, James D.ATSON, JAMES D.(1928- )
American molecular biologistJames D. Watson won the 1962 Nobel Prize in physiology and
medicine along with Francis Crickand Maurice Wilkins for
discovering the structure of DNA, or deoxyribonucleic acid, the
molecular carrier of genetic information. Watson and Crick had
worked as a team since meeting in the early 1950s, and their
research ranks as a fundamental advance in molecular biology.
James Dewey Watson was born in Chicago, Illinois, on
April 6, 1928, to James Dewey and Jean (Mitchell) Watson.
He was educated in the Chicago public schools, and during his
adolescence became one of the original Quiz Kids on the radio
show of the same name. Shortly after this experience in 1943,
Watson entered the University of Chicago at the age of 15.Watson graduated in 1946, but stayed on at Chicago for
a bachelor’s degree in zoology, which he attained in 1947.
During his undergraduate years Watson studied neither genet-
ics nor biochemistry—his primary interest was in the field of
ornithology. In 1946, Watson spent a summer working on
advanced ornithology at the University of Michigan’s summer
research station at Douglas Lake. During his undergraduate
career at Chicago, Watson had been instructed by the well-
known population geneticist Sewall Wright, but he did not
become interested in the field of genetics until he read Erwin
Schrödinger’s influential book What Is Life?It was then,
Horace Judson reports in The Eighth Day of Creation: Makers
of the Revolution in Biology,that Watson became interested in
finding out the secret of the gene.
Watson enrolled at Indiana University to perform grad-
uate work in 1947. Indiana had several remarkable geneticists
who could have been important to Watson’s intellectual devel-
opment, but he was drawn to the university by the presence of
the Nobel laureate Hermann Joseph Muller, who had demon-
strated 20 years earlier that x rays cause mutation. None-
theless, Watson chose to work under the direction of the Italian
biologist Salvador Edward Luria, and it was under Luria that
he began his doctoral research in 1948.
Watson’s thesis was on the effect of x rays on the rate of
phage lysis (a phage, or bacteriophage, is a bacterial virus).
The biologist Max Delbrück and Luria—as well as a number
of others who formed what was to be known as “the phage
group”—demonstrated that phages could exist in a number of
mutant forms. A year earlier Luria and Delbrück had published
one of the landmark papers in phage genetics, in which they
established that one of the characteristics of phages is that they
can exist in different genetic states so that the lysis (or burst-
ing) of bacterial host cells can take place at different rates.
Watson’s Ph.D. degree was received in 1950, shortly after his
twenty-second birthday.
Watson was next awarded a National Research Council
fellowship grant to investigate the molecular structure of pro-
teins in Copenhagen, Denmark. While Watson was studying
enzyme structure in Europe, where techniques crucial to the
study of macromolecules were being developed, he was also
attending conferences and meeting colleagues.
From 1951 to 1953, Watson held a research fellowship
under the support of the National Foundation for Infantile
Paralysis at the Cavendish Laboratory in Cambridge, England.
Those two years are described in detail in Watson’s 1965
book, The Double Helix: A Personal Account of the Discovery
of the Structure of DNA.An autobiographical work, The
Double Helixdescribes the events—both personal and profes-
sional—that led to the discovery of DNA. Watson was to work
at the Cavendish under the direction of Max Perutz, who was
engaged in the x-ray crystallography of proteins. However, he
soon found himself engaged in discussions with Crick on the
structure of DNA. Crick was 12 years older than Watson and,
at the time, a graduate student studying protein structure.
Intermittently over the next two years, Watson and Crick
theorized about DNA and worked on their model of DNA
structure, eventually arriving at the correct structure by recog-
nizing the importance of x-ray diffraction photographs pro-womi_W 5/7/03 10:18 AM Page 594