Chapter 01
The Main Themes of
Microbiology
Lecture Outline
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Section 1.1:
The Scope of Microbiology
Learning Outcomes
• List the various types of microorganisms.
• Identify multiple professions using microbiology.
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The Scope of Microbiology (1)
Microbiology: the specialized area of biology that deals with
organisms too small to be seen with the naked eye
• Microorganisms or microbes
• Germs, viruses, or agents
• “Bugs”
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The Scope of Microbiology (2)
Major groups of microorganisms:
• Bacteria
• Algae
• Protozoa
• Helminths
• Fungi
• Viruses: noncellular, parasitic, protein-coated genetic
elements that cause harm to host cells
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The Scope of Microbiology (3)
Microbes are easy and difficult to study
• Reproduce rapidly, large populations can be grown in the
laboratory
• Can’t be seen directly, must be analyzed through indirect
methods in addition to using microscopes
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The Scope of Microbiology (4)
Microbiologists study:
• Cell structure and function
• Growth and physiology
• Genetics
• Taxonomy and evolutionary history
• Interactions with living and nonliving environment
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Branches of Microbiology (1)
Medical Microbiology
• Deals with microbes that cause
diseases in humans and animals
Public Health Microbiology and
Epidemiology
• Monitor and control the spread of
diseases in communities
• USPHS, CDC, WHO
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Branches of
Microbiology (2)
Immunology
• Complex web of protective
substances and cells produced in
response to infection
• Includes vaccination, blood testing,
and allergy
• Role of the immune system in
cancer and autoimmune diseases
Industrial Microbiology
• Safeguards our food and water
• Biotechnology
• Microbes used to create amino
acids, beer, drugs, enzymes, and
vitamins
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Branches of
Microbiology (3)
Agricultural Microbiology
• Relationships between microbes and
domesticated plants and animals
• Plant specialists, animal specialists
Environmental Microbiology
• Study the effect of microbes on the
earth’s diverse habitats
• Aquatic, soil, and geomicrobiology,
and astrobiology
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Concept Check (1)
• What types of organisms are considered microbes?
• What types of cells can viruses infect?
• List and describe three branches of microbiology.
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Section 1.2:
The Impact of Microbes on Earth:
Small Organisms with a Giant Effect
Learning Outcomes
• Describe the role and impact of microbes on the earth.
• Explain the theory of evolution and why it is called a theory.
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The Impact of Microbes on Earth (1)
•
Microbes have shaped the development of the
earth’s habitats and the evolution of other life forms
for billions of years
•
Single-celled organisms arose 3.5 billion years ago
and were the only living inhabitants until ~2.9 billion
years ago
•
Bacteria, archaea, and eukaryotes arose from the
last universal common ancestor (LUCA)
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The Impact of Microbes on Earth (2)
Eukary: true nucleus
• Cells with a nucleus are classified as eukaryotes
Prokary: pre nucleus
• Bacteria and archaea do not have a nucleus and have been
traditionally classified as prokaryotes
• This classification is no longer used because bacteria and
archaea are so distant genetically
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Evolutionary Time Line
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The Impact of Microbes on Earth (3)
Bacteria are ubiquitous. They are found:
• deep in the earth’s crust
• polar ice caps
• oceans
• inside the bodies of plants and animals
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The Impact of Microbes on Earth (4)
Evolution: the accumulation of changes that occur in
organisms as they adapt to their environments
Theory of Evolution:
• Documented every day in all corners of the planet
• An observable phenomenon testable by science
• A label for a well-studied and well-established natural
phenomenon
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Microbial Involvement in
Shaping Our Planet (1)
Microbes are deeply involved in the flow of energy and
food through the earth’s ecosystems
• Bacteria: anoxygenic photosynthesis
• The production of oxygen by microbes allowed species
diversification
• Photosynthetic microorganisms (bacteria and algae) account
for more than 70% of the earth’s photosynthesis, contributing
the majority of the oxygen to the atmosphere
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Examples of Microbial Habitats:
Pond with Algae
(a) © Jerome Wexler/Science Source
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Microbial Involvement in
Shaping Our Planet (2)
Decomposition:
• Breakdown of dead matter
and wastes
• Accomplished by bacteria
and fungi
(b) © Michel & Christine Denis-Huot/Science Source
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Microbial Involvement in
Shaping Our Planet (3)
Microbes are the main forces that drive the structure
and content of soil, water, and atmosphere
• Gas production by microbes
• Microbes living within the earth’s crust
• Bacteria and fungi living in complex associations with plants
and animals
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Concept Check (2)
• Describe the difference between a prokaryote and
a eukaryote.
• Describe the basic tenets of the Theory of
Evolution.
• True/False: Microscopic organisms produce more
oxygen than plants.
• True/False: More than 50% of the microbes on the
planet live below the earth’s crust.
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Section 1.3:
Human Use of Microbes
Learning Outcome
• Explain one old way and one new way that humans
manipulate organisms for their own uses.
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Human Use of Microorganisms (1)
Humans have been using microorganisms for
thousands of years to improve life and even shape
civilizations
• Yeast for production of bread, wine, and beer
• Other fungi used for cheese production
• Moldy bread used in Egypt to treat wounds
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Human Use of Microorganisms (2)
Biotechnology:
• Manipulation of microorganisms
to make products in an industrial
setting
Genetic Engineering:
(a) NREL/US Department of Energy/Dennis Schroeder
• Manipulates the genetics of
microbes, plants, and animals for
the purpose of creating new
products and genetically
modified organisms (GMOs)
(b) © Bloomberg via Getty Images
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Human Use of Microorganisms (3)
Recombinant DNA
technology:
• Techniques that allow the
transfer of genetic material
from one organism to
another and deliberately
alter DNA
Bioremediation:
• Introduction of microbes
into the environment to
restore stability or to clean
up toxic pollutants
(c) © Accent Alaska.com/Alamy
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Concept Check (3)
• Name three products produced by genetically
modified organisms that benefit humans.
• Describe one method in which microbes are used
for bioremediation.
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Section 1.4:
Infectious Diseases and the Human Condition
Learning Outcome
• Summarize the relative burden of human disease caused by
microbes, emphasizing the differences between developed
countries and developing countries.
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Infectious Diseases and
the Human Condition (1)
Pathogen: any agent such as a virus, bacterium, fungus,
protozoan, or helminth that causes disease
• Nearly 2000 different microbes can cause disease
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Top Causes of Death—All Diseases
United States
No. of Deaths
Worldwide
No. of Deaths
1. Heart disease
611,105
1. Heart disease
7.3 million
2. Cancer
584,881
2. Stroke
6.7 million
3. Chronic lower respiratory
diseases
149,205
3.Lower-respiratory infections
(influenza and pneumonia)*
3.1 million
4. Accidents (unintentional
injuries)
130,557
4. Chronic obstructive pulmonary
disease
3.1 million
5. Stroke (cerebrovascular
diseases)
128,978
5. Trachea, bronchus, lung
cancers
1.6 million
6. Alzheimer’s disease
84,767
6. HIV/AIDS
1.5 million
7. Diabetes
75,578
7. Diarrheal diseases
1.5 million
8. Influenza and pneumonia
56,979
8. Diabetes
1.5 million
9. Nephritis, nephrotic syndrome,
and nephrosis
47,112
9. Road injury
1.3 million
10. Intentional self-harm (suicide)
41,149
10. Hypertensive heart disease
1.1 million
Diseases most clearly caused by microorganisms: influenza, pneumonia, HIV/AIDS, and diarrheal diseases
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Causes of Death in the United States
and the World
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Infectious Diseases and
the Human Condition (2)
Malaria:
• Kills between 440,000 and 700,000 people every year
• Transmitted by mosquitoes
• Prevention of infection is through the use of bed nets, which
although inexpensive, are too expensive for poor families
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Infectious Diseases and
the Human Condition (3)
New (emerging) diseases as well as older (reemerging)
diseases are increasing
• Ebola, AIDS, hepatitis C, and viral encephalitis
Polio, leprosy, and parasitic worm diseases have largely
been eradicated
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Infectious Diseases and
the Human Condition (4)
Certain diseases once considered noninfectious are
now found to be caused by microbes:
• Gastric ulcers caused by Helicobacter pylori
• Link between certain cancers and bacteria and viruses
• Cocksackie virus has been associated with diabetes and
schizophrenia
• Multiple sclerosis, OCD, coronary artery disease, obesity
linked to chronic microbial infections
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Infectious Diseases and
the Human Condition (5)
First Golden Age of Microbiology: “obvious” diseases
were characterized and cures or preventions were
devised
Today, we are discovering the subtler side of
microorganisms and the quiet, slow, destructive
diseases they cause
• Female infertility caused by Chlamydia infection
• Liver cancer (hepatitis viruses) and cervical cancer (human
papillomavirus)
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Infectious Diseases and
the Human Condition (6)
An increasing number of patients with weakened
immune systems are subject to infections by common
microbes not pathologic to healthy people
Drug-resistant microbes also contribute to the increase
in infectious disease
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Concept Check (4)
• True/False: All microbes cause disease.
• Why is there a difference between the top 10 causes
of death in the United States versus worldwide?
• Name three connections between diseases
considered to be noninfectious and a microbe.
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Section 1.5:
The General Characteristics
of Microorganisms
Learning Outcomes
• Differentiate among bacteria, archaea, and eukaryotic
microorganisms.
• Identify a fourth type of microorganism.
• Compare and contrast the relative sizes of the different
microbes.
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General Characteristics of Microorganisms (1)
Bacterial and Archaeal cells:
• About 10x smaller than eukaryotic cells
• Lack organelles: small, double-membrane-bound structures
that perform specific functions
The majority of microorganisms are single-celled (all
bacterial and archaeal and some eukaryotes)
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Cell Structure
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General Characteristics of Microorganisms (2)
Helminths (worms) are not microorganisms but are
included in the study of infectious disease:
• They are transmitted similarly to bacterial diseases
• The human body responds to them in the same way as it
responds to bacterial diseases
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Five Types of Microorganisms
Top Left) CDC; (Middle Left) CDC/Dr. Lucille K. Georg; (Bottom Left) © Nancy Nehring/E+/Getty Images RF; (Bottom Center) CDC/Janice Carr; (Bottom Right) CDC
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Lifestyles of Microorganisms
Majority of microorganisms:
• Live in habitats such as soil and water
• Are relatively harmless and often beneficial
• Derive food and other factors from the nonliving environment
Parasites:
• Harbored and nourished by the host
• Cause damage and disease in the host
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Concept Check (5)
• In terms of size, how are eukaryotes different from
bacteria and archaea?
• Give three examples of eukaryotic organelles.
• Why are helminths (worms) considered in the study
of microbiology?
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