CHAPTER
1
A Brief History of Microbiology
Chapter Outline
The Early Years of Microbiology (pp. 2–7)
What Does Life Really Look Like?
How Can Microbes Be Classified?
The Golden Age of Microbiology (pp. 7–17)
Does Microbial Life Spontaneously Generate?
What Causes Fermentation?
What Causes Disease?
How Can We Prevent Infection and Disease?
The Modern Age of Microbiology (pp. 17–21)
What Are the Basic Chemical Reactions of Life?
How Do Genes Work?
Chapter Summary
The Early Years of Microbiology (pp. 2–7)
The early years of microbiology brought the first observations of microbial life and the initial
efforts to organize them into logical classifications.
What Does Life Really Look Like?
Antoni van Leeuwenhoek (1632–1723), a Dutch tailor, made the first simple microscope in
order to examine the quality of cloth. The device was little more than a magnifying glass with
Instructor’s Manual for Microbiology with Diseases by Body Systems, 5e
How Can Microbes B e Classified?
During the 18th century, Carolus Linnaeus (1707–1778), a Swedish botanist, developed a
taxonomic system for naming plants and animals and grouping similar organisms together.
Biologists still use a modification of Linnaeus’s taxonomy today.
All living organisms can be classified as either eukaryotic or prokaryotic. Prokaryotic
organisms are unicellular microbes that lack a true nucleus. Eukaryotic organisms are
organisms whose cells contain a nucleus composed of genetic material surrounded by a distinct
membrane. Within these categories, microorganisms are further classified as follows:
Bacteria are single-celled prokaryotes whose cell walls are composed of peptidoglycan
Fungi are relatively large microscopic eukaryotes and include multicellular molds and
single-celled yeasts. These organisms obtain their food from other organisms and have cell
Algae are plant-like eukaryotes that are photosynthetic; that is, they make their own food
from carbon dioxide and water using energy from sunlight. The algae include multicellular
The Golden Age of Microbiology (pp. 7–17)
During what is now sometimes called the “Golden Age of Microbiology,” from the late 19th to
the early 20th century, microbiologists competed to be the first to answer several questions
about the nature of microbial life.
Does Microbial Life Spontaneously Generate?
The theory of spontaneous generation (or abiogenesis) proposes that living organisms can
arise from nonliving matter. It was proposed by Aristotle (384–322 B.C.) and was widely
accepted for almost 2000 years, until experiments by Francesco Redi (1626–1697) challenged it.
Chapter 1 A Brief History of Microbiology
The debate over spontaneous generation led in part to the development of a generalized
scientific method by which questions are answered through observations of the outcomes of
carefully controlled experiments. It consists of four steps:
2. The scientist generates a hypothesis—a potential answer to the question.
4. Based on the observed results of the experiment, the scientist either accepts, rejects, or
Video Tutor: The Scientific Method
What Causes Fermentation?
Pasteur’s investigations into the cause of fermentation led to the discovery that yeasts are
facultative anaerobes, growing with or without oxygen. He also determined that anaerobic
bacteria ferment grape juice to produce acids, whereas yeast cells ferment grape juice to produce
alcohol. These discoveries suggested a method to prevent the spoilage of wine by heating the
grape juice just enough to kill contaminating bacteria, so that it could then be inoculated with
What Causes Disease?
Prior to the 1800s, disease was attributed to various factors such as evil spirits, astrological
signs, imbalances in body fluids, and foul vapors. Pasteur’s discovery that bacteria are
responsible for spoiling wine led to his hypothesis in 1857 that microorganisms are also
responsible for diseases, an idea that came to be known as the germ theory of disease.
Microorganisms that cause specific diseases are called pathogens. Today, we know that
Instructor’s Manual for Microbiology with Diseases by Body Systems, 5e
greatest achievements was the elaboration, in his publications on tuberculosis, of a set of steps
that must be taken to prove the cause of any infectious disease. These four steps are now known
as Koch’s postulates:
1. The suspected causative agent must be found in every case of the disease and be absent from
healthy hosts.
3. When the agent is introduced into a healthy, susceptible host, the host must get the disease.
4. The same agent must be re-isolated from the diseased experimental host.
How Can We Prevent Infection and Disease?
In the mid-19th century, modern principles of hygiene, such as those involving sewage and
water treatment, personal cleanliness, and pest control, were not widely practiced. Medical
A few years later, English physician Joseph Lister (1827–1912) advanced the idea of
antisepsis in health care settings, reducing deaths among his patients by two-thirds with the use
of phenol. Florence Nightingale (1820–1910), the founder of modern nursing, introduced
antiseptic techniques that saved the lives of innumerable soldiers during the Crimean War of
humans.
The field of immunology, the study of the body’s specific defenses against pathogens, began
with the experiments of English physician Edward Jenner (1749–1823), who showed that
vaccination (also called immunization) with pus collected from cowpox lesions prevented
Chapter 1 A Brief History of Microbiology
The Modern Age of Microbiology (pp. 17–21)
Since the early 20th century, microbiologists have worked to answer new questions in new
fields of science.
What Are the Basic Chemical Reactions of Life?
Biochemistry is the study of metabolism. It began with Pasteur’s work on fermentation and
Buchner’s discovery of enzymes but was greatly advanced by the proposition of microbiologists
Albert Kluyver (1888–1956) and C. B. van Niel (1897–1985) that biochemical reactions are
How Do Genes Work?
Microbial genetics is the study of inheritance in microorganisms. Throughout the 20th century,
researchers working with microbes made significant advances in our understanding of how
genes work. Investigations with microbes demonstrated that DNA is the genetic material. Other
studies established that a gene’s activity is related to the function of the specific protein coded
by that gene, and they determined the exact way in which genetic information is translated into a
protein.
What Roles Do Microorganisms Play in the Environment?
Environmental microbiology studies the role microorganisms play in their natural
environment. Bioremediation is the use of living microbes to detoxify polluted environments.
Microbial communities play an essential role, for example, in the decay of dead organisms and
How Do We Defend Against Disease?
The germ theory of disease shows microbes can cause disease, but the body can defend itself.
Although the work of Jenner and Pasteur marked the birth of the field of immunology, the
discovery of chemicals in the blood that are active against specific pathogens advanced the field
Instructor’s Manual for Microbiology with Diseases by Body Systems, 5e
What Will the Future Hold?
Among the questions microbiologists are working to answer today are the following:
How can we develop successful programs to control or eradicate diseases such as
tuberculosis, malaria, AIDS, and Ebola?
What is it about the physiology of life forms known only by their nucleic acid sequences that
has prevented researchers from growing them in the laboratory?
Can bacteria and archaea be used in new ultraminiature technologies, such as living computer
circuit boards?
New Media Resources
Connecting Concepts: The Scientific Method and Epidemiology
Learning Catalytics: Assess students in real time using open-ended tasks to probe student
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