CHAPTER
1
I.
THE MICROBIAL WORLD AND
YOU
Introduction
Microbiology is a branch of biology which involves the study of
microorganisms. Microorganisms can be defined as living organisms which cannot
be seen by the unaided eyes. These organisms include bacteria, fungi, algae,
protozoa, viruses, etc.
II.
Intended Outcomes/ Learning Objectives
At the end of this chapter, you should be able to:
1. enumerate the different type of microorganisms
2. discuss the brief history of microbiology
3. list the beneficial activities of microorganism to humans
4. describe several infectious disease caused by microorganism
III.
Pre-test
Find out how much you already know about the topics in this module. Choose the
letter of the best answer.
_______1. The formal system for classifying and naming organisms was
developed by ______?
a. Robert Koch
b. Ignaz Semmelweis
c. Aristotle
d. Carolus Linnaeus
_______2. In the name Staphylococcus aureus, aureus is the ____?
a. Genus
b. Domain name
c. Species
d. Kingdom
_______3. Viruses are not considered living organisms because they _______?
a. can only be visualized
using
an
electron
microscope
b. are typically associated
with disease
c. cannot
reproduce
by
themselves
d. are ubiquitous in nature
_______4. Name the first scientist who discovered the cell in a piece of cork?
a. Louis Pasteur
b. Anton van Leeuwenhoek
c. Robert Hooke
d. Rudolf Virchow
_______5. Which of the following microbes is generally the smallest?
a.
b.
c.
d.
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bacteria
fungi
protozoa
viruses
_______6. The study of microbiology involves all of the following EXCEPT
________.
a.
b.
c.
d.
understanding more about chemical reactions inside cell
understanding how the immune system works
research on infectious disease agents
characterization of the tissues and organs of the human body
_______7. Which of the following is a scientific name?
a. Mycobacterium tuberculosis
b. Tubercle bacillus
_______8. The process of using microorganisms to clean up pollution created by
human activities is called _____________.
a. Biopesticides
b. Bioinsecticides
c. Bioremediation
d. Biopreservatives
_______9. Microorganisms are used in food production to yield products such as
_________.
a. Yogurt
b. Cheese
c. Acidophilus milk
d. All of the above
_______10. Identify which statement is incorrect.
a. Microorganisms produce
various organic acids.
b. Microorganisms are used
as biological control
agents.
c. All microorganism are
beneficial.
d. Microorganisms are used
to produce fermented
dairy products.
_______11. It is considered as the most primitive or oldest living organisms.
a. Bacteria
b. Archaea
c. Fungi
d. Viruses
_______12. What type of microorganism is yeast which is used in many food
preparations?
a. Bacteria
b. Algae
c. Fungi
d. Virus
_______13. He disproved the spontaneous generation theory.
a.
b.
c.
d.
Louis Pasteur
Anton van Leeuwenhoek
Joseph Lister
Edward Jenner
_______14. He is known as the “Father of bacteriology”.
a.
b.
c.
d.
Louis Pasteur
Anton van Leeuwenhoek
Joseph Lister
Edward Jenner
_______15. Unicellular microorganisms, prokaryotic and are simplest of all
microbial cells.
a.
b.
c.
d.
Bacteria
Fungi
Viruses
Algae
LESSON 1:
MICROBES IN OUR LIVES
What is Microbiology?

Microbiology is the study of microorganisms. These are organisms
too small to be seen clearly by the unaided eyes.
What are Microorganisms?

Microorganisms are organisms too small to be seen clearly by the
unaided eyes. They include fungi, bacteria, algae, protozoa and
viruses. Some microorganisms however, like the eukaryotic
microorganisms are visible without magnification. Examples are
bread molds and filamentous algae.
Microorganisms as cells
The cell is the fundamental unit of life. Two fundamental different types of
cells exist among microorganisms; they are prokaryotic and eukaryotic.

Prokaryotes - These microbial cells lack membrane-bound nucleus
and organelles.

Eukaryotes - Possess a membrane-bound nucleus and organelles.
Naming and Classifying Microorganisms
In a nomenclature system designed by Carolus Linnaeus (1735), each living
organism is assigned two names---- the genus (plural: genera) is the first name
and is always capitalized; the specific epithet (species name) follows and is not
capitalized.
For example, Staphylococcus aureus, a bacterium found on human skin.
Types of Microorganisms
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(1) Bacteria
- They are unicellular microorganisms, prokaryotic and are simplest of all
microbial cells.
- They are extremely diverse and numerous in soils and waters.
- Some are harmful while others are beneficial to man.
- Most bacteria have peptidoglycan cell wall and they divide by binary
fission.
- They are often described in terms of their general shaped.
(2) Archaea
- They are unicellular, simple organisms and are capable of surviving
under extreme conditions or environment that are very cold, very hot,
very basic, or very acidic.
- Considered as the most primitive or oldest living organisms.
- Unlike most bacteria, archaeal cell walls do not contain peptidoglycan.
(3) Fungi
- Fungi (mushrooms, molds and yeasts) have eukaryotic cells (with a true
nucleus). Most fungi are multicellular.
- Yeast are found in many different environments, some have beneficial
uses such as causing bread to rise and beverages to ferment but yeast
can also cause food to spoil and some even cause diseases.
- Molds are made up of long filaments that form visible colonies. They are
found in many different environments, from soil to rotting food to damp
bathroom corners. It plays a critical role in the decomposition of dead
plants and animals.
- Fungi obtain nutrients by absorbing organic material from their
environment.
- Many play beneficial roles while others cause diseases in plants,
animals and humans.
(4) Algae
- Are single-celled microscopic organisms, but some marine algae are
large, relatively complex, multicellular organisms.
- All algae photosynthesize their own food as plants do, and many can
move about.
- Algae are widely distributed in both fresh water and oceans. Because
they are so numerous and because they capture energy from sunlight in
the food they make, algae are an important source of food for other
organisms.
- Many consumer products contain ingredients derived from algae such
as salad dressing, lipstick, toothpaste, and some brands of ice cream.
- Agar which is used in microbiology laboratory to grow microorganisms
is also derived from algae.
(5) Protozoa
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-
-
Are single celled, eukaryotic organisms that are usually motile.
Some move with help of hair like structures like cilia or whip-like
structures like flagella, some with cytoplasmic extensions called
pseudopods “false feet”.
Many protozoa obtain food by engulfing or ingesting smaller
microorganisms.
Protozoa are found in a variety of water and soil environments.
(6) Viruses
- They are noncellular or acellular entities which means they are not
composed of cell.
- A virus consist of proteins and genetic material--- either DNA or RNA but
never both.
- They are the smallest microorganisms and can only be viewed under an
electron microscope.
- They only reproduce when present within living cells.
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ACTIVITY
Name: _____________________________________
Date: _________________
Score: ________
Microorganism Crossword
Direction: Complete the crossword puzzle below. Use the definitions as a clue
to the word that goes into the corresponding blank spaces.
Down
1 noncellular entities that are
parasites of cells
2 primary producers in food chains in
aquatic habitat
3 organisms too small to be seen
clearly by the unaided eyes
4 cells that possess a membranebound nucleus and organelles
Across
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5 microorganism that obtain nutrients
by absorbing organic material from
their environment
6 organisms which are usually motile
7 simplest of all microbial cells
8 microbial cells that lack membranebound nucleus and organelles
LESSON 2:
BRIEF HISTORY OF MICROBIOLOGY
Discovery of Microorganisms
The advent of the microscope permitted the studying of microorganisms.
The first microscopes were simple ground glass lenses that magnified images of
previously unseen microorganisms. Among the first to observe this previously
unseen and invisible microbial world were Robert Hooke and Anton Van
Leeuwenhoek.
1. Robert Hooke
 An English mathematician and natural historian.
 He coined the term “cells” to describe the “little boxes” he observed in
examining cork slices with a compound microscope.
 He was the first to make a known description of microorganisms.
2. Anton Van Leeuwenhoek
 Lived in Delft, Holland. He was a draper and an amateur microscope
builder.
 He learned lens grinding as a hobby and made over 100 simple
microscopes each capable of magnifying an image about 300 times.
 By using simple microscopes, he observed microscopic organisms
which he called ‘animalcules’.
 He discovered bacteria in 1676.
 He made sketches of the different shapes of bacteria.
 He was the first person to publish extensive and accurate
observations of microorganisms.
 He is known as the father of bacteriology.
After Van Leeuwenhoek’s death, the study of microbiology did not develop
rapidly because microscopes were rare and interest in microorganisms was not
high. Scientists then were debating the theory of spontaneous generation.
The Spontaneous Generation Conflict
The concept spontaneous generation states that living organisms could
develop from non-living matter. The proponents of the concept of spontaneous
generation claim that living organisms could develop from non-living or
decomposing matter.
1. Francesco Redi challenged this concept by showing that maggots on
decaying meat came from fly eggs deposited on the meat, and not from
the meat itself.
2. John Needham showed that mutton broth boiled in flasks and then
sealed could still develop microorganisms, which supported the theory
of spontaneous generation.
3. Lazzaro Spallanzani showed that flasks sealed and then boiled had no
growth of microorganisms, and he proposed that air carried germs to the
culture medium. He also commented that external air might be needed
to support the growth of animals already in the medium.
4. Rudolf Virchow introduced the concept of biogenesis which states that
living cells can arise only from preexisting cells.
5. Louis Pasteur demonstrated that microorganisms are in the air
everywhere and offered proof of biogenesis. He devised a series of
swan necked flasks known as Pasteur-flasks, filled the flasks with broth
and heated the broth to sterilization. After cooling, the flasks were
opened to the air, but bends on the neck of the flasks prevented
microorganisms from falling on the broth and contaminating it rather the
microorganisms fell on the neck of the bottle. Pasteur proved that no
growth occurred because dust and germs were trapped on the wall of
the curved necks. If the neck were broken, growth will occur. By these
experiments he disproved and defeated the theory of spontaneous
generation.
Apart from the defeat of the concept of spontaneous generation,





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Pasteur’s work led to an effective sterilization method which involve
holding juices and milk at 62.80C (1450F) for 30 minutes known as
Pasteurization.
He discovered that alcoholic fermentation was catalyzed by Living
Yeast Cells.
He developed vaccines for the diseases anthrax, fowl cholera and
rabies between 1880 and 1890.
He postulated the Germ Theory of Disease which states that
microorganisms are the cause of infectious diseases.
Pasteur’s work ushered in the Golden Age of Microbiology.
The Recognition of the Role of Microorganisms in Disease
1. Joseph Lister developed a system of surgery designed to prevent
microorganisms from entering wounds. He implemented the use of
sterile surgical instrument, and used carbolic acid (phenol) during
surgery and on wound dressings.
2. Robert Koch was a German physician. He was the first to directly
prove the role of microorganisms in causing diseases. Koch’s
outstanding achievement was the formulation of four postulates to
associate a particular organism with a specific disease.
3. Edward Jenner used a vaccination procedure to protect individuals
from smallpox.
4. Paul Ehrlich introduced an arsenic-containing chemical called
salvarsan to treat syphilis. Ehrlich also coined the term
chemotherapy.
5. Alexander Fleming observed that the mold (fungus) Penicillium
inhibited the growth of bacterial culture. He named the active
ingredient penicillin. Penicillin has been used clinically as an
antibiotic since the 1940’s.
Modern Developments in Microbiology
1. New branches of microbiology were developed.
 Bacteriology is the study of bacteria.
 Mycology is the study of fungi.
 Parasitology is the study of parasitic protozoa and
worms.
 Immunology is the study of immunity.
 Virology is the study of virus.
2. The microbiologists are using genomics, the study of all of an
organism’s genes to classify bacteria, fungi and protozoa.
3. The study of AIDS, analysis of the action of interferons, and the
development of new vaccines are among the current research
interests in immunology.
4. New techniques in molecular biology and electron microscopy have
provided tools for advancement of our knowledge in virology.
5. The development of recombinant DNA technology has helped
advance all areas in microbiology.
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ACTIVITY
Name: _____________________________________
Date: _________________
Score: ________
SUPERSTARS OF MICROBIOLOGY!
Direction: Match the following scientist to their contributions in the field of
microbiology.
_____Alexander Fleming
_____Rudolf Virchow
_____Edward Jenner
_____Joseph Lister
_____Robert Koch
_____Robert Hooke
_____Anton Van Leeuwenhoek
_____Louis Pasteur
_____Paul Ehrlich
a. First to observe bacteria
b. First to use disinfectants in
surgical procedures
c. Proved that microorganisms
cause diseases
d. Introduced an arseniccontaining chemical to treat
syphilis
e. Said that living things arise
from preexisting cells
f. Developed vaccine against
small pox
g. Disproved spontaneous
generation
h. First to observe cells
i. Developed penicillin
j. First to characterize a virus
LESSON 3:
MICROBES AND HUMAN WELFARE
Microorganisms as Friends
Microorganisms have found application in various aspects of life.
They are useful in food industries to produce many food substances, in
Microorganisms
medicine as
to Friends
produce vaccines and antibiotics, in environmental
protection, and in agriculture to optimize yield.
Microorganisms have found application in various aspects of life. They are
A. Microorganisms
and Food
Production in medicine to produce
useful in food industries
to produce many
food substances,
vaccines and antibiotics, in environmental protection, and in agriculture to optimize
yield.
 Many microorganisms are used to produce many of the
foods and beverages we consume. Most of these food
A. Microorganisms and Food Production
products are produced by fermentation.
 Fermentation is the process of converting
 Many microorganisms are used to produce many of the foods and
carbohydrates to alcohol or organic acids using
beverages we consume. Most of these food products are
microorganisms—yeasts or bacteria—under anaerobic
produced by fermentation.
conditions.
 Fermentation is the process of converting carbohydrates to
 Pickles and some sausages are also produced by
alcohol or organic acids using microorganisms—yeasts or
fermentation processes.
bacteria—under anaerobic conditions.
 Microorganisms are used to produce fermented dairy
 Pickles and some sausages are also produced by fermentation
products such as cheese, yoghurt and acidophilus milk.
processes.
 They are also used to produce alcoholic beverages
 Microorganisms are used to produce fermented dairy products
such as beer by conversion of sugar to alcohol and
such as cheese, yoghurt and acidophilus milk.
carbon dioxide.
 They are also used to produce alcoholic beverages such as beer
by conversion of sugar to alcohol and carbon dioxide.
B. Production of Pharmaceuticals
B. Production of Pharmaceuticals
Microorganisms are used to produce different pharmaceuticals
such as antibiotics, steroids vitamins, hormones, etc.
Microorganisms are used to produce different pharmaceuticals such as
antibiotics, steroids
hormones,
etc.
 vitamins,
Antibiotics
are microbially
produced substances or
substances synthetically derived from natural sources that
 Antibiotics are microbially produced substances or substances
inhibit or kill microorganisms.
synthetically derived from natural sources that inhibit or kill
 Steroids regulate various aspects of human metabolisms
microorganisms.
and are produced by organisms such Rhizopus nigricans.
 Steroids regulate various aspects of human metabolisms and are
 Vaccines are produced using microorganisms with the
produced by organisms such Rhizopus nigricans.
antigenic properties to elicit a primary immune response;
 Vaccines are produced using microorganisms with the antigenic
they are used to prevent many once deadly diseases such
properties to elicit a primary immune response; they are used to
as polio, small pox, tuberculosis, measles, diphtheria and
prevent many once deadly diseases such as polio, small pox,
whooping cough.
tuberculosis, measles, diphtheria and whooping cough.
 Vitamins are essential animal nutritional factors; some
vitamins are produced by microbial fermentation, e.g.
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Riboflavin produced by various species of Clostridium and
Ashbya gossypii.
 Human insulin and human growth hormone are
produced by genetically engineered bacteria.


Vitamins are essential animal nutritional factors; some vitamins are
produced by microbial fermentation, e.g. Riboflavin produced by
various species of Clostridium and Ashbya gossypii.
Human insulin and human growth hormone are produced by
genetically engineered bacteria.
C. Production of Organic Acids
Various organic acids are produced by microorganisms examples are:



Citric acid: used as a food additive especially in the production of
soft drinks.
Gibberellic acid: a plant hormone is formed by the fungus. It is used
as growth promoting substances to stimulate plant growth flowering
and seed germination.
Lactic acid: used in foods as preservatives, cosmetics, in leather
production and textile industry.
D. Microorganisms and Agriculture
Agriculture
microorganisms.




depends
in
many
ways
on
the
activities
of
Microorganisms help in nitrogen fixation used by plants for growth.
Microorganisms in the rumen of ruminant animals such as cattle and
sheep also help in the digestion of cellulose present in grasses on
which they feed on.
Microorganisms help in the cycling of nutrients such as carbon,
nitrogen and sulphur which are needed to maintain ecological
balance.
Microorganisms are also used as biological control agents. Fungi,
bacteria and viruses can be used as bioinsecticides or
biospesticides, e.g. Bacillus thuringensis
E. Microorganisms and the Environment



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Microorganisms can be used to clean up pollution created by human
activities in a process called bioremediation.
Pollutants such as pesticides, spilled oil solvents which could pose
human health hazard are degraded to nontoxic substances by
microorganisms.
Microorganisms are used to degrade wastes and pollutants so as to
maintain and restore environmental quality.
F. Sewage Treatment
 Microorganisms are also used in sewage treatment. Especially
cultured microbes are used in the biological treatment of sewage and
industrial waste effluent in a process known as bio augmentation.
These microbes help to get rid of waste materials which could have
accumulated in the environment.
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ACTIVITY
Name: ______________________________
Date: _________________
Score: ________
Direction: Answer the following questions.
1. Briefly state the role of microorganism in each of the following:
a. Food production
________________________________________________________
________________________________________________________
________________________________________________________
b. Agriculture
________________________________________________________
________________________________________________________
________________________________________________________
c. Sewage Treatment
________________________________________________________
________________________________________________________
________________________________________________________
d. Pharmaceuticals
________________________________________________________
________________________________________________________
________________________________________________________
2. Find at least three supermarkets products made by microorganisms. (Hint:
The label will state the scientific name of microorganism or include the
word culture, fermented, or brewed.)
________________________________________________________
________________________________________________________
________________________________________________________
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LESSON 4:
MICROBES AND HUMAN DISEASE
Normal Microbiota
We all lived in a world filled with microbes, from birth until death, and we all
have a variety of microorganisms on and inside our bodies. These microorganisms
make up our normal microbiota or flora. Although the normal microbiota do us
no harm, and in some cases actually benefit us, under some circumstances they
can make us sick or infect people we contact.
Resistance is the ability to ward off diseases. Important resistance is
provided by the barrier of the skin, mucous membranes, cilia, and stomach acids.
Microbes can be destroyed by white blood cells, the inflammatory response, fever,
and by specific responses in our immune system. Sometimes when our natural
defenses are not strong enough to overcome an invader, they have to be
supplemented by antibiotics or drugs.
The disease-producing properties of a species of microbe and the host’s
resistance are important factors in determining whether a person will contract a
disease.
Microorganisms as Disease Agents
Microbial diseases are still the major cause of death in many developing
countries. Microorganisms cause different diseases in man such as:





AIDS (Acquired Immune Deficiency Syndrome) caused by the
Human Immuno Deficiency Virus (HIV).
Tuberculosis caused by a bacterium, Mycobacterium tuberculosis.
Cholera caused by a bacteria Vibrio cholera.
Malaria caused by four species of the Protozoa called Plasmodium
transmitted by the female anopheles mosquito.
Escherichia coli O157:H7 causes bloody diarrhea when it grows in
the intestines.
Emerging Disease is a new or changing disease showing an increase in
incidence in the recent past or a potential to increase in the near future. Examples
are bird flu and swine flu.
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Microorganisms are also agents of diseases of plants and animals of
agricultural importance. These microbial diseases of plants and animals cause
major economic losses in the agriculture industry and to the world.
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ACTIVITY
Name: ____________________________
Date: _________________
Score: ________
1. Do a research on several infectious or emerging infectious disease
caused by microorganism. List and describe at least five of these microbial
diseases.
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
___________________________________________________________
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ASSIGNMENT
ESSAY
Direction: Answer the following questions.
1. How does understanding of microbiology affect your life?
2. Describe briefly the contributions of the following scientists in the
development of microbiology:
(a) Leeuwenhoek
(b) Spallanzani
(c) Pasteur
(d) Koch
(e) Lister
(f) Fleming
3. In what ways do microbes be beneficial?
4. In what ways might microbes be harmful?
5. List five diseases cause by microorganisms. Do not include those already
mentioned above.
6. List three characteristics for each of the following microorganisms.
(a) Bacteria
(b) Archaea
(c) Fungi
(d) Protozoa
(e) Viruses
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