‫كلية العلوم الطبيه التطبيقيه‬
‫قسم تقنية املختبرات الطبيه‬
GENERAL MEDICAL
MICROBIOLOGY
MDL 234
Dr. Heavin Hannan
Microbial World and You
What is Microbiology?
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Micro - too small to be seen with the naked
eye
Bio - life
ology - study of or ( Science )
A Brief History of
Microbiology
The First Observations

1. Robert Hooke observed that cork was composed
of “little boxes”; he introduced the term cell
(1665).
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2. Hooke’s observations laid the groundwork for
development of the cell theory, the concept that all
living things are composed of cells.
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3. Anton van Leeuwenhoek, using a simple
microscope, was the first to observe
microorganisms (1673).
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4. Louis Pasteur demonstrated that
microorganisms are in the air everywhere
and offered proof of biogenesis (1861).
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5. Pasteur’s discoveries led to the
development of aseptic techniques used in
laboratory and medical procedures to
prevent contamination by microorganisms.
Microbes in Our Lives
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1. Living things too small to be seen with the unaided eye
are called microorganisms.
2. Microorganisms are important in the maintenance of an
ecological balance on Earth.
3. Some microorganisms live in humans and other
animals and are needed to maintain good health.
4. Some microorganisms are used to produce foods and
chemicals.
5. Some microorganisms cause disease.
Organisms included in the study
of Microbiology
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1. Bacteria
2. Protozoans
3. Algae
4. Parasites
5. Yeasts and Molds
• Fungi

6. Viruses

Bacteriology
 Protozoology
 Phycology
 Parasitology

Mycology
 Virology
Microorganisms - Microbes - Germs
5 Kingdoms of Living Organisms
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1. Animalia
2. Plantae
3. Fungi
4. Protista
5. Monera - Bacteria and Cyanobacteria
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Eukaryotic vs. Prokaryotic
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Difference between prokaryotic
and eukaryotic cells (1/3):
Example
Eukaryotic
Prokaryotic
Fungi, human cell
Bacteria
True nucleus
Nuclear membrane
Nuclear
Material
Absent
Nucleoli
Multiple
chromosome
Single
chromosome
Histones associated
with DNA
No histone
Cytoplasmic
Structure
Difference between prokaryotic
and eukaryotic cells (2/3):
Eukaryotic Prokaryotic
Division
Mitosis
Simple
binary
fission
Mitochondria
Present
Absent
Present
Absent
Microtubular
cytoskeleton
Present
Absent
Rough
endoplasmic
reticulum
Ribosome
80S
70S
Difference between prokaryotic
and eukaryotic cells (3/3):
Cytoplasmic
membrane
Cell wall
Prokaryotic
Eukaryotic
Contain sterol
No sterol
(mycoplasma
contains
cholsesterol)
No mesosome
Mesosome
lipoprotein
Contain
lipoprotein
Absent (fungi Present (except
in mycoplasma)
have chitin
instead)
5 Characteristics of Life
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1. Cells
2. Maintain structure by taking up
chemicals and energy from the environment
3. Respond to stimuli in the external
environment
4. Reproduce and pass on their organization
to their offspring
5. Evolve and adapt to the environment
Taxonomic Classification
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Kingdom
Phylum
Class
Order
Family
Genus
species
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Escherichia coli
Non assigned for bacteria
Proteobacteria
Gamma-Proteobacteria
Enterobacteriales
Enterobacteriaceae
Escherichia
coli
Naming and Classifying
Microorganisms
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In a nomenclature system designed by Carolus
Linnaeus (1735), each living organism is
assigned two names.
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The two names consist of a Genus and a species
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Genus and species are either underlined or
italicized
Binomial System of Taxonomic
Classification
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Genus
Escherichia
species
coli

Staphylococcus
aureus
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Genus is always capitilized
species is never capitilized
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Classification System
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3 Domains
1978 Carl Woese
• 1. Bacteria
• Unicellular prokaryotes with cell wall containing
peptidoglycan
• 2. Archaea
• Unicellular prokaryotes with no peptodoglycan in
cell wall
• 3. Eukarya
•
•
•
•
Protista
Fungi
Plantae
Animalia
Domain Comparison
BACTERIA
Absent
ARCHEA
Absent
EUKARYA
Present
Membrane
Organelles
Absent
Absent
Present
Peptidoglycan
Cell Wall
Present
Absent
Absent
Ribosomes
Present
Present
Present
Nuclear
Envelope
Tree of Life
Bacterial Classification
The old system of classification
Based on phenotypic characteristics
Bacteria were classified into:
1. Higher bacteria:
a. Actinomyces (filamentous branching
organism).
b.
Leptothrices
(filamentous
non
branching organism).
2. Lower bacteria:
Simple unicellular organisms classified
on the basis of some traits as:
a. Shape of the bacterial cell:
cocci: spherical.
bacilli: rod- shaped.
Vibrios: comma- shaped.
spirilla: spiral- shaped
b. Ability to form spores.
c. Method of energy production:
glycolysis for anaerobes
cellular respiration for aerobes
d. Nutritional requirements.
e. Reaction to the Gram stain
It differentiates bacteria into two groups:
Gram-positive bacteria (violet in color)
Gram-negative bacteria (pink in color)
it distinguishes between two fundamentally
different kinds of bacterial cell walls.
f. Pathogenicity:
Saprophytes:
live on dead material, soil, water, dust... etc. They
almost never cause disease.
Parasites:
live in the body of living creatures, they can be
pathogenic or non pathogenic.
pathogenic:
cause disease e.g. Mycobacterium tuberculosis
Neisseria gonorrhoeae
Non pathogenic (commensal bacterial flora) :
Bacteria which don't normally cause diseases
and can be found in healthy individuals.
The New System of Classification
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The new system of classification is based on
genotypic characteristics which introduce
new criteria for bacterial relatedness.
Examples for new criteria
introduced by genotypic
characteristics
1- Nucleotide base composition:
The parameter most often used is the mol
percent of guanine plus cytosine (G + C)
in the total DNA.
For any one species, the G + C content is
relatively fixed and this provides a basis
for classification.
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2- Nucleic base homology:
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Organisms can be classified into groups on
the basis of the homology of their DNA
base sequences.
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When a mixture of DNA from two related
species is used, hybrid pairs of DNA strands
are produced.
3- More recently, Genome sequencing:
It is nucleotide base sequences especially of
their ribosomal RNA (rRNA) is being used
in the classification.
This technique is based on base sequence
homologies in ribosomal RNA.
It has provided new insights into the
evolutionary relationships among the
bacteria.
Bacteria - what comes to mind?
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Diseases
Infections
Epidemics
Food Spoilage
Only 1% of all known bacteria cause human
diseases
About 4% of all known bacteria cause plant
diseases
95% of known bacteria are non-pathogens
Microbes Benefit Humans
1.Bacteria are primary decomposers - recycle
nutrients back into the environment (sewage
treatment plants)
2. Microbes produce various food products
• cheese, pickles, sauerkraut, green olives
• yogurt, soy sauce, vinegar, bread
• Beer, Wine, Alcohol
3. Microbes are used to produce Antibiotics
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Penicillin
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Mold
• Penicillium notatum
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1928 Alexander Fleming
4. Bacteria synthesize chemicals that our
body needs, but cannot synthesize
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Example: E. coli
• B vitamins - for metabolism
• Vitamin K - blood clotting
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Escherichia coli
• Dr. Escherich
• Colon (intestine)
5. Biochemistry and Metabolism
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Very simple structure
rapid rate of reproduction
provides “instant” data
6. Microbial Antagonism
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Our normal microbial flora prevents
potential pathogens from gaining access to
our body
7. Insect Pest Control
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Using bacteria to control the growth of
insects
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Bacillus thuringiensis
• caterpillars
• bollworms
• corn borers
8. Bioremediation
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Using microbes to clean up pollutants and
toxic wastes
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2 Genera
• Pseudomonas sp.
• Bacillus sp.
9. Recombinant DNA Technology
Gene Therapy
Genetic Engineering
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Bacteria can be manipulated to produce
enzymes and proteins they normally would
not produce
• Insulin
• Human Growth Hormone
• Interferon
10. Microbes form the basis of
the food chain
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Marine and fresh water microorganisms
Koch - 1st to use Agar to solidify
culture media
Golden Age of Microbiology
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1857 - 1914
Pasteur
• Pasteurization
• Fermentation
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Joseph Lister
• Phenol to treat surgical wounds – 1st attempt to control infections
caused by microoganisms
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Robert Koch
• Koch’s Postulates
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Edward Jenner
• vaccination
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Paul Erlich
• 1st synthetic drug used to treat infections
• Salvarsan - arsenic based chemical to treat Syphilis
• “salvation” from Syphilis
Naming of Bacteria
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Genus and species - Binomial System of
Taxonomic Classification
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Information usually given:
• 1. Describes an organism
• 2. Identifies a habitat
• 3. Honors a scientist or researcher
Microbes do benefit us, but they
are also capable of causing many
diseases
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Pneumonia
Botulism
Cholera
Syphilis
Chlamydia
Meningitis
Strep Throat
Black Plague
Whooping Cough
Typhoid Fever
Scarlet Fever
Gonorrhea
Tuberculosis
Tetanus
Lyme Disease
Diarrhea
Measles
Mumps
Herpes 1
Herpes 2
RMSV
AIDS
Gangrene