Microbiology
 Definition:
Microbiology is the science that studies organisms which ordinarily are too
small to be seen without a microscope. These organisms are referred to as
microorganisms or microbes. Among these microorganisms are
-All of the following may be considered microorganisms:
1.
2.
3.
4.
5.
6.
bacteria (eubacteria, archaebacteria)
fungi (yeasts, molds)
protozoa
microscopic algae
viruses
various parasitic worms
Why to study microbiology?
 Medical microbiology
Microbes both cause and prevent disease.
Microbes produce antibiotics used to treat disease.
The single most important achievement of modern medicine is the ability to treat
or prevent microbial disease.
Most of this course will consider the physiology of microbes and their role in
disease.
 Pathogen
A microorganism is considered to be a pathogen or pathogenic if it is capable of
producing disease.
1. Though only a minority of microorganisms is pathogenic, practical
knowledge of microbes is necessary for their treatment so is highly
relevant to medicine and related health sciences.
 Ecology:
Recycle nutrients. Some bacteria are able of converting nitrogen into its usable
compounds to be used by plants, etc.
 Industrial applications:
• Production of beer, wine, bread
• Gasohol
• Genetic recombination and Biotechnology.
• New species to produce all kinds of proteins (pseudomonas: eat up pollutants)
• Acetobacter produces cellulose fibers (strong fabric)
• Genetic engineered tomatoes: change a gene to slow the rate of ripening, stay
fresher longer thereby increasing shelf life.
 Environmental microbiology
2. Basic environmental processes:
The existence and functioning of microbes is absolutely crucial to environmental
health.
By health, microbes are absolutely necessary for such basic things as:
1. making nutrients available from non-living sources
2. providing energy to ecosystems
3. freeing up nutrients from no longer living sources

1.
2.
3.
4.
Without microorganisms we would:
Have no oxygen to breath
Nothing to eat
Not be able to utilize the energy in food even if we could eat it
Not be able move about without constantly tripping over the bodies of
dead organisms
In more technical terms, a sampling of what microorganisms are and do
environmentally includes:
1.
2.
3.
4.
microbes are producers
microbes are nitrogen fixers
microbes are decomposers
microbes are symbionts and endosymbionts
 Industrial microbiology
Microbes have played important roles in manufacturing products for as long as
there has been history.
Microorganisms are used to:
1. Ferment useful chemicals (ethanol, acetone, etc.)
2. Produce certain food stuffs (wine, cheese, yogurt, bread, half sour pickles,
etc.)
3. Produce of recombinant products (recombinant insulin, human growth
hormone, etc.)
4. Destroy wastes (sewage, oil spills, bioremediation)
 Normal flora [normal micro biota]
Not disease-causing:
Normal flora is those not-typically-disease-causing microorganisms normally
found in and on healthy individuals.
Very abundant:
Normal flora is extremely abundant in terms of absolute numbers.
A normal human has approximately 1013 body cells and 1014 individual normal
flora!
Transient micro biota
Normal flora that is not always present or is present for only a few days, weeks,
or months before disappearing. All found externally:
1.
2.
3.
4.
5.
6.
7.
8.
 Normal flora is found mostly:
On the skin
In the eyes
In the nose
In the mouth
In the upper throat
In the lower urethra
In the lower intestine
Especially in the large intestine
 Micro-organisms exist everywhere in nature:
- Soil, air, water, the table top, your stomach
• Micro-organisms in water directly impact water quality:
- Transmission of diseases (pathogens)
- bad tastes, or odours (e.g. hydrogen sulphide)
- Corrosion or bio fouling of surfaces
 History of Microbiology
 Development of microscopy:
 Aristotle (384-322) and others believed that living organisms could develop
from non-living materials.
 1590: Hans and Zacharias Janssen (Dutch lens grinders) mounted two
lenses in a tube to produce the first compound microscope.
 1931: Ernst Ruska constructed the first electron microscope.
 Spontaneous generation disagreement:
 1688: Francesco Redi (1626-1678) was an Italian physician who disproves the
idea of spontaneous generation by showing that rotting meat carefully kept from
flies will not spontaneously produce maggots.
 1836: Theodor Schwann (1810-1882) helped develop the cell theory of living
organisms, namely that that all living organisms are composed of one or more
cells and that the cell is the basic functional unit of living organisms.
 1876: Robert Koch (1843-1910). German bacteriologist was the first to cultivate
anthrax bacteria outside the body using blood serum at body temperature.
Building on Pasteur’s "germ theory", he subsequently published "Koch's
postulates.
 1861: Louis Pasteur's (1822-1895) famous experiments with swan-necked
flasks finally proved that microorganisms do not arise by spontaneous
generation. This eventually led to:
- Development of sterilization
- Development of aseptic technique
- 1660: Robert Hooke (1635-1703) published "Micrographic", containing
drawings and detailed observations of biological materials made with the
best compound microscope and illumination system of the time.
- 1676: Anton van Leeuwenhoek (1632-1723) was the first person to
observe microorganisms.
- 1835 Augustine Basis de Lodi showed that a disease affecting silkworms
was caused by a fungus - the first microorganism to be recognized as a
contagious agent of animal disease.
 Robert Koch (1876)
Showed that sheep Anthrax was caused by a bacterium. A rod shaped, large,
and could form spores.
Discovered this by developing a method for isolating pure cultures of one
specific kind of bacteria. Solid media (before always grown in broth –
Mixed culture).
On solid media each isolated bacterium grows and divides into giving rise to a
pure colony.
Koch could then demonstrate that a particular bacterial species was the cause
of a particular disease.
Koch even introduced a set of criteria for others who wanted to prove that a
specific microbe causes a specific disease.
 Nomenclature
• Classification of (all) life on earth based on 7 categories:
Kingdom:
Phylum:
Class:
Order:
Family:
Genus: (always capital, italic)
Species: (lower case, italic)
• Common bacteria: E. coli
- Genus: Escherichia, species: coli
Protists
• Most micro-organisms belong to Kingdom ‘Protista’ protists)
- Higher protists (eukaryotes – organized cell)
- Lower protists (prokaryotes – simple cell structure)
• Protista are not animals or plants
• Many are uni-cellular, some multi-cellular
Protozoa
Unicellular engulfers:
Protozoa are unicellular, eukaryotic organisms that derive nourishment from
their liquid environment, often by engulfment.
Cyanobacteria [blue-green algae]:
Cyanobacteria, also known as blue-green algae, are photosynthetic bacteria.
Not to be confused with true algae which are eukaryotes?
Fungi [yeast, mold]
Fungi are eukaryotic organisms including yeasts (single celled) and molds
(multicelled).
Defining characteristics include:
Cell walls, often composed of chitin
Obtaining of nourishment by the absorbing of extracellular digested solutions of
organic material found in their environment.
 Eukaryotic cell
 Prokaryotic cell
 Bacteria
Bacteria are simple, cellular organisms lacking a nucleus as well as other
characteristics of prokaryotes which distinguish them from organisms that have
nucleated cells.
That is, bacteria are prokaryotes.
• Bacteria: Lower protests, prokaryotic (simple) cells
• Hundreds – thousands of bacteria
• Mostly single-celled organisms, in 4 basic shapes:
- Spherical (cocci),
- Cylindrical rods (bacilli),
- Curved or helical rods (vibrio and spirilla), and
- Filaments (multi-cellular)
 Shapes of bacterial cells
Pathogenic micro-organisms
• Pathogenic bacteria cause many diseases of man
• ‘Enteric’ bacteria cause water borne diseases:
- Escherichia coli (E. coli): diarrhea, urinary tract infection
- Salmonella typhimurium: diarrhea, fever, nausea
- Salmonella typhi : typhoid fever
- Shigella (several species): dysentery
- Vibrio cholera: cholera
Shapes of bacterial cell:
 Viruses
• Sub-microscopic particles, much smaller than bacteria
• must live & replicate in a living host animal
→ Therefore: ALL viruses are parasitic
• Viruses are very host specific
Viruses
• Example virus form:
- T-shaped viruses
• Has single RNA or DNA strand,
Surrounded in a protein coat
Viruses are infectious agents
Viruses are not cellular and therefore are classified as neither prokaryotes nor
eukaryotes.
Viruses are obligate, intracellular parasites of cellular organisms.
Pathogenic viruses
• Viruses cause many water-borne diseases:
- entero viruses: gastro-enteritis (mild-severe diarrhea)
- Hepatitis A virus: infective hepatitis
- Polio virus: polio
- Coxsackie virus: disease of central nervous system
- Other virus: trachoma (eye infections, blindness)
Fungi
 Fungi: higher protests have eukaryotic cells
• Have vegetative structure ‘mycelium’:
- Rigid branching system of tubes carrying cytoplasm
- Forms by germination and outgrowth of single spore cell
• Yeasts are uni-cellular fungi with no mycelium
• Fungi important for decomposing organic matter
• Are mostly aerobic organisms
Examples of fungi
Algae
• Algae: uni-cellular or multicellular higher protests
• All algae have light absorbing pigments (e.g. chlorophyll)
• Conduct photosynthesis, producing oxygen:
6CO2+ 6H2O + nutrients → 6CH2O + 6O2
• Range in size from single cells to large branched forms
• Freshwater and saltwater species
Algae are eukaryotic organisms that derive nourishment from both their
chemical and their physical environment (i.e., they are photosynthetic).
 Protozoa
• Protozoa: higher protests (eukaryotic cells), aerobic
• Mobile organisms: amoeba motion, flagella, or cilia
• Several protozoa cause water-borne diseases:
- Endameba histolytica amoebic dysentery
- Giardia lambliagiardiasis (diarrhea, nausea, fever)
Microbiology, b. 1674
Origin of Microbes: Pasteur’s Swan-Necked Flasks
Origin of Microbes: Pasteur’s Swan-Necked Flasks
Origin of Microbes: Reid’s Exp.
Relationship of Microbes
Scale of Microbes
Microscope of Antony van Leeuwenhoek (1632-1723)