WORLD OF MICROBIOLOGY & IMMUNOLOGYviii•
Introductionled to the development of modern, molecularly oriented
genetics.
Recently microbiology has been a major contributor to
the rise of molecular biology, the branch of biology dealing
with the physical and chemical bases of living matter and its
function. Microbiologists have been deeply involved in stud-
ies of the genetic code and the mechanisms of DNA, RNA,
and protein synthesis. Microorganisms were used in many of
the early studies on the regulation of gene expression and the
control of enzyme activity. In the 1970s new discoveries in
microbiology led to the development of recombinant gene
technology and genetic engineering. One indication of the
importance of microbiology today is the number of Nobel
Prizes awarded for work in physiology and medicine during
the twentieth century; about a third of these were awarded to
scientists working on microbiological problems.
Microorganisms are exceptionally diverse, are found
almost everywhere, and affect human society in countless
ways. The modern study of microbiology is very different
from the chemically and medically oriented discipline pio-
neered by Louis Pasteur and Robert Koch. Today it is a large
discipline with many specialities. It has impact on medicine,
agricultural and food sciences, ecology, genetics, biochem-
istry, and many other fields. Today it clearly has both basic and
applied aspects.
Many microbiologists are interested in the biology of the
microorganisms themselves. They may focus on a specific
group of microorganisms and be called virologists (scientists
who study viruses), bacteriologists (scientists who study bac-
teria), phycologists or algologists (scientists who study algae),
mycologists (scientists who study fungi), or protozoologists
(scientists who study protozoa). Others may be interested in
microbial morphology or particular functional processes and
work in fields such as microbial cytology, physiology, ecolo-
gy, genetics, taxonomy, and molecular biology. Some microbi-
ologists may have a more applied orientation and work on
problems in fields such as medical microbiology, food and
dairy microbiology, or public health. Because the various
fields of microbiology are interrelated, an applied microbiolo-
gist must always be familiar with basic microbiology. For
example, a medical microbiologist must have a good under-
standing of microbial taxonomy, genetics, immunology, and
physiology to identify and properly respond to the pathogen of
concern.
It is clear that scientists study the microbial world in
much the same way as they studied the world of multicellular
organisms at the beginning of the twentieth century, when
microbiology was a young discipline. This is in part due to the
huge developments and refinements of techniques, which now
allow scientists to more closely and fully investigate the world
of bacteria and viruses.
One of the focuses of this book is the field of medical
microbiology and its connection with immunology. Medical
microbiology developed between the years 1875 and 1918,
during which time many disease-causing bacteria were identi-
fied and the early work on viruses begun. Once people realized
that these invisible agents could cause disease, efforts weremade to prevent their spread from sick to healthy people. The
great successes that have taken place in the area of human
health in the past 100 years have resulted largely from
advances in the prevention and treatment of infectious disease.
We can consider the eradication of smallpox, a viral disease,
as a prime example. The agent that causes this disease is one
of the greatest killers the world has ever known—and was
probably the greatest single incentive towards the formaliza-
tion of the specialized study of immunology. Research into the
mechanism of Edward Jenner’s “vaccination” discovery—he
found that of a patient injected with cow-pox produces immu-
nity to smallpox—laid the foundations for the understanding
of the immune system and the possibility of dealing with other
diseases in a similar way. Because of an active worldwide vac-
cination program, no cases of smallpox have been reported
since 1977. (This does not mean, however, that the disease
cannot reappear, whether by natural processes or bioterror.)
Another disease that had a huge social impact was bubon-
ic plague, a bacterial disease. Its effects were devastating in
the Middle Ages. Between 1346 and 1350, one third of the
entire population of Europe died of bubonic plague. Now gen-
erally less than 100 people die each year from this disease. The
discovery of antibiotics in the early twentieth century provid-
ed an increasingly important weapon against bacterial dis-
eases, and they have been instrumental in preventing similar
plague epidemics.
Although progress in the application of immunological
research has been impressive, a great deal still remains to be
done, especially in the treatment of viral diseases (which do
not respond to antibiotics) and of the diseases prevalent in
developing countries. Also, seemingly “new” diseases contin-
ue to arise. Indeed, there has been much media coverage in the
past twenty years in the U.S. of several “new” diseases,
including Legionnaires’ disease, toxic shock syndrome, Lyme
disease, and acquired immunodeficiency syndrome (AIDS).
Three other diseases emerged in 1993. In the summer of that
year a mysterious flu-like disease struck the Southwest, result-
ing in 33 deaths. The causative agent was identified as a virus,
hantavirus, carried by deer mice and spread in their droppings.
In the same year, more than 500 residents of the state of
Washington became ill with a strain of Escherichia colipres-
ent in undercooked beef prepared at a fast-food restaurant. The
organism synthesized a potent toxin and caused haemolytic-
uremic syndrome. Three children died. In 1993, 400,000 peo-
ple in Milwaukee became ill with a diarrheal disease, cryp-
tosporidiosis, that resulted from the improper chlorination of
the water supply.
It is a great credit to the biomedical research community
that the causative agents for all these diseases were identified
very soon after the outbreaks. The bacteria causing
Legionnaires’ disease and Lyme disease have only been iso-
lated in the past few decades, as have the viruses that cause
AIDS. A number of factors account for the fact that seeming-
ly “new” diseases arise almost spontaneously, even in indus-
trially advanced countries. As people live longer, their ability
to ward off infectious agents is impaired and, as a result, the
organisms that usually are unable to cause disease becomewomi_fm 5/6/03 1:34 PM Page viii