Introduction to microbiology

Welcome to Microbiology 1
For Today…
Introduction to the course
Explore the history and foundation of
microbiology
Dimensional Analysis

Chapter 1
The Microbial World and You

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.

Microbes (benefits):
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

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.

History of Microbiology
Ancestors of bacteria were the first life on Earth.

The first microbes were observed in 1673.
In 1665, Robert Hooke (Englishman) reported
that living things were composed of little
boxes or cells.

1673-1723, Antoni van
Leeuwenhoek (Dutch)
described live
microorganisms that
he observed in teeth
scrapings, rain water,
and peppercorn
infusions.

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?

Conditions Results
3 jars covered with
fine net
No maggots
3 open jars Maggots appeared
From where did the maggots come?
What was the purpose of the sealed jars?
Spontaneous generation or biogenesis?
Redi filled six jars with decaying meat.

Redi placed meat in three containers. One
was uncovered, a second was covered
with paper, and the third was covered with
fine gauze that would exclude flies.
Flies laid their eggs on the uncovered
meat and maggots developed.
The other two pieces of meat did not
produce maggots spontaneously.

However, flies we attracted to the
gauze-covered container and laid their
eggs on the gauze; these eggs
produced maggots.
Thus the generation of maggots by
decaying meat resulted from the
presence of fly eggs, and meat did not
spontaneously generate maggots.

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.

Rudolf Virchow (German) presented
biogenesis: living cells can arise only from
preexisting cells.

Read up on the historical contribution(s) of
microbiology made by:
John Needem (1713-1781)
Lazzaro Spallanzani (1729-1799)
Theodore Schwann (1810-1882)
Theodorvon Dusch (1824-1890)

1861: Louis Pasteur demonstrated that
microorganisms are present in the air.
Conditions Results
Nutrient broth placed
in flask, heated, not
sealed
Microbial growth
Nutrient broth placed
in flask, heated, then
sealed
No microbial growth
Spontaneous generation or biogenesis?

Pasteur experiment –
Pasteur first filtered air through cotton and
found that objects resembling plant spores
had been trapped.
If a piece of the cotton was placed in sterile
medium after air had been filtered through it,
microbial growth occurred.
Next he placed nutrients solutions in flasks,
heated their necks in a flame, and drew them
out into a variety of curves.

Cont’d
The swan neck flasks that he produced in
this way had necks open to the atmosphere.
Pasteur then boiled the solutions for a few
minutes and allowed them to cool. No
growth took place even though the contents
of the flasks were exposed to the air.
Pasteur pointed out that no growth occurred
because dust and germs had been trapped
on the walls of the curved necks.

Cont’d
If the neck were broken, growth
commenced immediately.

Pasteur’s S-shaped flask kept microbes out
but let air in. These experiments form the
basis of aseptic technique

The Golden Age of Microbiology
1857-1914
Beginning with Pasteur’s work, discoveries
included the relationship between microbes
and disease, microbes and fermentation,
immunity, and antimicrobial drugs

Pasteur showed that microbes are
responsible for fermentation (Germ theory of
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).

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.

The Germ Theory of Disease
1835: Agostino Bassi showed a silkworm
disease was caused by a fungus.
1865: Pasteur believed that another silkworm
disease was caused by a protozoan.
1840s: Ignaz Semmelwise advocated
handwashing to prevent transmission of
puerperal fever from one OB patient to
another.

• 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.

1876: Robert Koch provided proof that a
bacterium causes anthrax and provided the
experimental steps, Koch’s postulates, used
to prove that a specific microbe causes a
specific disease.
Koch was a physician and Pasteur’s young
rival

Koch's Postulates
are used to
prove the cause
of an infectious
disease.

Koch's Postulates
are a sequence
of experimental
steps to relate a
specific microbe
to a specific
disease.

A young milkmaid informed the physician
Edward Jenner that she could not get
smallpox because she had already been
sick from cowpox.
1796: Edward Jenner inoculated a person
with cowpox virus. The person was then
protected from smallpox.
Called vaccination from vacca for cow
The protection is called immunity

What can you say about the cowpox and
smallpox viruses?

Vaccinations
produced from avirulent microbial strains
produced from live viruses
produced from viral particles

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.

Chemotherapy – treatment with chemicals
• 1910: Paul Ehrlich developed a synthetic
arsenic drug, salvarsan, to treat syphilis.
• 1930s: Sulfonamides were synthesized.

1928: Alexander
Fleming discovered
the first antibiotic.
He observed that
Penicillium fungus
made an antibiotic,
penicillin, that killed
S. aureus (bacteria).
1940s: Penicillin was
tested clinically and
mass produced.

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.

Read up on these branches of
microbiology and their uses of
microorganism, for example:
Environmental Microbiology
Industrial Microbiology
Agricultural microbiology

Scope of Microbiology
Microorganisms are usually divided into
six subgroups:
Bacteria, archaea, alage, fungi,
protozoa, and viruses. These
subgroups are not close related.
Bacteria are less like archaea or algae
or fungi or protozoa or virus than a
shark is like a giraffe or an orchid is like
an eagle.

Scope of Microbiology
These are grouped based on the
techniques for identifying, cultivating
and studying which are similar.
Read up on primary distinction among
sub groups.
Example: prokaryotes and eukaryotes.

Classification of Microbes
Taxonomy
• The science of classifying organisms
• Provides universal names for organisms
• Provides a reference for identifying
organisms

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

Taxonomic Hierarchy
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Dumb
Kings
Play
Chess
On
Funny
Green
Square
s

Taxonomic Hierarchy
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Binomal
Nomenclature uses
the Genus and
Species name to
identify each
creature.

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

Bacteria (or Eubacteria)
Most abundant on earth
They are nitrogen fixers and recycle carbon
No membrane bound organelles

Archaea
Methanogens
Halophiles
Hyperthermophiles

•Eukaryotic species:
•A group of closely related organisms that breed
among themselves
•Prokaryotic species:
•A population of cells with similar characteristics
•Clone: Population of cells derived from a single cell
•Strain: Genetically different cells within a clone
•Viral species:
•Population of viruses with similar characteristics
that occupies a particular ecological niche

Let’s examine some microbes
Paramecium caudatum
Euglena acus
Peridiniumis - a dinoflagellate

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.

• 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.

• When a pathogen overcomes the host’s
resistance, disease results.
• Emerging Infectious Diseases (EID): New
diseases and diseases increasing in
incidence

Major Taxonomic Groups of Bacteria
per Bergey’s manual
Gracilicutes – gram-negative cell walls, thin-
skinned
Firmicutes – gram-positive cell walls, thick
skinned
Tenericutes – lack a cell wall & are soft
Mendosicutes – archaea, primitive
procaryotes with unusual cell walls &
nutritional habits

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).

Introduction to microbiology

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