The Main Themes of
Microbiology
Chapter 1
Section 1.1
THE SCOPE OF MICROBIOLOGY
Microbiology
• 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”
Major Groups of Microorganisms
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Bacteria
Algae
Protozoa
Helminths
Fungi
Viruses: non-cellular, parasitic, proteincoated genetic elements
Study of Microbes is Easy AND Difficult
• 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
Aspects of Microbiological Study
• Medical Microbiology
• Public health
Microbiology and
Epidemiology
• Immunology
Aspects of Microbiological Study
• Industrial
Microbiology
• Agricultural
Microbiology
• Environmental
Microbiology
Check Your Understanding
• What types of organisms are considered microbes?
Provide some examples of these organisms.
• What types of cells can viruses infect?
• List and describe three branches of microbiology.
Identify professions that make use of microbiology.
Section 1.2
THE IMPACT OF MICROBES
ON EARTH: SMALL ORGANISMS
WITH A GIANT EFFECT
The Impact of Microbes on Earth
• 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
• Bacteria, archaea, and
eukaryotes arose from
this ancestor
Types of Cells
• Eukaryotes: true nucleus
– Cells with a nucleus are classified as eukaryotes
• Prokaryotes: “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 distinct genetically
Bacteria are Ubiquitous
• Can be found:
– Deep in the earth’s crust
– Polar ice caps
– Oceans
– Inside the bodies of plants and animals
Photosynthesis
• Involved in the flow of energy and food
through the earth’s ecosystems
• Photosynthetic microorganisms account
for more than 70% of the earth’s
photosynthesis
– Production of oxygen by oxygenic
photosynthesis evolved later allowing a
diversification of species
Decomposition
• Breakdown of dead
matter and wastes
• Accomplished by
bacteria and fungi
Microbes Are Vital In Shaping Earth
• 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
Check Your Understanding
• Describe the difference between a prokaryote and a
eukaryote.
• Describe the role and impact of microbes on the earth.
• 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.
Section 1.3
HUMAN USE OF MICROBES
Importance of Microbes to Humans
• 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
Uses for Microbes
• Biotechnology
– Manipulation of
microorganisms to make
products in an industrial
setting
• Genetic Engineering
– Manipulates the genetics of
microbes, plants, and animals
for the purpose of creating
new products and genetically
modified organisms (GMOs)
Uses for Microbes
• 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
Check Your Understanding
• Name three products produced by genetically modified
organisms that benefit humans.
• Describe one method in which microbes are used for
bioremediation.
Section 1.4
INFECTIOUS DISEASES AND
THE HUMAN CONDITION
Pathogen
• Any agent (virus,
bacterium, fungus,
protozoan, or helminth)
that causes disease
– Nearly 2,000 different
microbes cause disease
Combating Infectious Diseases
• New (emerging) diseases as well as older
(reemerging) diseases are increasing
– AIDS, hepatitis C and viral encephalitis
• Polio, leprosy, and parasitic worm
diseases have largely been eradicated
Knowledge of Diseases Is Improving
• 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
– The Borna agent has been linked to schizophrenia
Clinical Work Against Disease Continues
• During the 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
• 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
Check Your Understanding
• True/False: All microbes cause disease.
• Why is there a difference between the top 10 causes of
death in the U.S. versus worldwide?
• Name three connections between diseases considered
to be noninfectious and a microbe.
Section 1.5
GENERAL CHARACTERISTICS
OF MICROORGANISMS
General Categories of Microbes
Bacteria and Archaea
• About 10x smaller than eukaryotic cells
• Lack organelles: small, double-membranebound structures that perform specific
functions
• All bacterial and archaeal cells are singlecelled
Helminthes
• Not true 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
– Their identification requires use of
microscopes to view larvae and mouth parts
Five Types of Microbes