Introduction to Bacteriology
Chapter 1 The Microbial World and You
What is Microbiology?
Microbes, or microorganisms are minute
living things that are usually unable to be
viewed with the naked eye.
What are some examples of microbes?
Bacteria, fungi, protozoa, algae, viruses
are examples!
Some are pathogenic
“Germ” refers to a rapidly growing cell.
Chapter 1 The Microbial World and You
What is Microbiology?
Microbes:
Decompose organic waste
Are producers in the ecosystem by
photosynthesis
Produce industrial chemicals such as
ethyl alcohol and acetone
Produce fermented foods such as vinegar,
cheese, and bread
Chapter 1 The Microbial World and You
What is Microbiology?
Chapter 1 The Microbial World and You
What is Microbiology?
Knowledge of Microbes allows humans to
Prevent food spoilage
Prevent disease occurrence
Led to aseptic techniques to prevent
contamination in medicine and in
microbiology laboratories.
Chapter 1 The Microbial World and You
History of Microbiology
Ancestors of bacteria were the first life on Earth.
Chapter 1 The Microbial World and You
History of Microbiology
The first microbes were observed in 1673.
In 1665, Robert Hooke (Englishman) reported
that living things were composed of little
boxes or cells.
Chapter 1 The Microbial World and You
History of Microbiology
1673-1723, Antoni van
Leeuwenhoek (Dutch)
described live
microorganisms that
he observed in teeth
scrapings, rain water,
and peppercorn
infusions.
Chapter 1 The Microbial World and You
History of Microbiology
Many believed spontaneous generation:
life can arise from non-living matter
In 1668, the Italian physician Francesco
Redi performed an experiment to disprove
spontaneous generation.
Can you think of an experiment that could
disprove spontaneous generation?
Chapter 1 The Microbial World and You
History of Microbiology
Redi filled six jars with decaying meat.
Conditions
Results
3 jars covered with
fine net
3 open jars
No maggots
Maggots appeared
From where did the maggots come?
What was the purpose of the sealed jars?
Spontaneous generation or biogenesis?
Chapter 1 The Microbial World and You
History of Microbiology
So now there are two hypotheses:
The hypothesis that living organisms arise
from nonliving matter is called spontaneous
generation. According to spontaneous
generation, a “vital force’ Forms life.
The Alternative hypothesis, that the living
organisms arise from preexisting life, is
called biogenesis.
Chapter 1 The Microbial World and You
History of Microbiology
1861: Louis Pasteur demonstrated that
microorganisms are present in the air.
Conditions
Results
Nutrient broth placed Microbial growth
in flask, heated, not
sealed
Nutrient broth placed No microbial growth
in flask, heated, then
sealed
Spontaneous generation or biogenesis?
Chapter 1 The Microbial World and You
History of Microbiology
Next experiment, Pasteur’s S-shaped flask kept
microbes out but let air in. These experiments
form the basis of aseptic technique
Chapter 1 The Microbial World and You
History of Microbiology
The Golden Age of Microbiology
1857-1914
Beginning with Pasteur’s work, discoveries
included the relationship between microbes
and disease, immunity, and antimicrobial
drugs
Chapter 1 The Microbial World and You
History of Microbiology
Pasteur showed that microbes are
responsible for fermentation.
Fermentation is the conversation of sugar to
alcohol to make beer and wine.
Microbial growth is also responsible for
spoilage of food.
Bacteria that use alcohol and produce acetic
acid spoil wine by turning it to vinegar (acetic
acid).
Chapter 1 The Microbial World and You
History of Microbiology
Pasteur demonstrated that
these spoilage bacteria
could be killed by heat that
was not hot enough to
evaporate the alcohol in
wine. This application of a
high heat for a short time
is called pasteurization.
Chapter 1 The Microbial World and You
History of Microbiology
The Germ Theory of Disease
• 1860s: Joseph Lister used a chemical
disinfectant to prevent surgical wound
infections after looking at Pasteur’s work
showing microbes are in the air, can spoil
food, and cause animal diseases.
Chapter 1 The Microbial World and You
History of Microbiology
Koch's Postulates
are used to
prove the cause
of an infectious
disease.
Chapter 1 The Microbial World and You
History of Microbiology
Koch's Postulates
are a sequence
of experimental
steps to relate a
specific microbe
to a specific
disease.
Chapter 1 The Microbial World and You
History of Microbiology
Chemotherapy – treatment with chemicals
• Chemotherapeutic agents used to treat
infectious disease can be synthetic drugs
or antibiotics.
• Antibiotics are chemicals produced by
bacteria and fungi that inhibit or kill other
microbes.
• Quinine from tree bark was long used to
treat malaria.
Chapter 1 The Microbial World and You
History of Microbiology
Chemotherapy – treatment with chemicals
• 1910: Paul Ehrlich developed a synthetic
arsenic drug, salvarsan, to treat syphilis.
• 1930s: Sulfonamides were synthesized.
Chapter 1 The Microbial World and You
History of Microbiology
1928: Alexander
Fleming discovered
the first antibiotic.
He observed that
Penicillium fungus
made an antibiotic,
penicillin, that killed
S. aureus.
1940s: Penicillin was
tested clinically and
mass produced.
Chapter 1 The Microbial World and You
Modern Developments
• Bacteriology is the study of bacteria.
• Mycology is the study of fungi.
• Parasitology is the study of protozoa and
parasitic worms.
• Recent advances in genomics, the study of
an organism’s genes, have provided new
tools for classifying microorganisms.
Chapter 1 The Microbial World and You
Classification of Microbes
Taxonomy
• The science of classifying organisms
• Provides universal names for organisms
• Provides a reference for identifying
organisms
Chapter 1 The Microbial World and You
Classification of Microbes
Taxonomy
• Systematics or phylogeny
• The study of the evolutionary history
of organisms
• All Species Inventory (2001-2025)
• To identify all species of life on Earth
Chapter 1 The Microbial World and You
Classification of Microbes
Taxonomic Hierarchy
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Dumb
Kings
Play
Chess
On
Funny
Green
Squares
Chapter 1 The Microbial World and You
Classification of Microbes
Taxonomic Hierarchy
Binomal
Nomenclature uses
the Genus and
Species name to
identify each
creature.
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Chapter 1 The Microbial World and You
Classification of Microbes
Taxonomic Hierarchy
Each name is Latinized
There is a specific way to write each name.
Homo sapiens
The first word is capitalized
Name is in italics
Homo sapiens
H. sapiens
Chapter 1 The Microbial World and You
Chapter 1 The Microbial World and You
Chapter 1 The Microbial World and You
Chapter 1 The Microbial World and You
Bacteria (or Eubacteria)
Most abundant on earth
They are nitrogen fixers and recycle carbon
No membrane bound organelles
Chapter 1 The Microbial World and You
Archaea
Methanogens
Halophiles
Hyperthermophiles
Chapter 1 The Microbial World and You
Classification of Microbes
Chapter 1 The Microbial World and You
Microbes and Human Disease
• Bacteria were once classified as plants
which gave rise to use of the term flora for
microbes.
• This term has been replaced by microbiota.
• Microbes normally present in and on the
human body are called normal microbiota.
Chapter 1 The Microbial World and You
Microbes and Human Disease
• Normal microbiota prevent growth of
pathogens.
• Normal microbiota produce growth factors
such as folic acid and vitamin K.
• Resistance is the ability of the body to
ward off disease.
• Resistance factors include skin, stomach
acid, and antimicrobial chemicals.
Chapter 1 The Microbial World and You
Microbes and Human Disease
• When a pathogen overcomes the host’s
resistance, disease results.
• Emerging Infectious Diseases (EID): New
diseases and diseases increasing in
incidence
species –a collection of bacterial cells which share an
overall similar pattern of traits in contrast to other
bacteria whose pattern differs significantly
strain or variety – a culture derived from a single
parent that differs in structure or metabolism from
other cultures of that species (biovars, morphovars)
type – a subspecies that can show differences in
antigenic makeup (serotype or serovar), susceptibility
to bacterial viruses (phage type) and in pathogenicity
(pathotype).