MICROBIOLOGY AND
PARASITOLOGY
MARY JOCELYN V. BATTUNG, PhD.
Burton’s Microbiology for the Health Sciences
has been written primarily for nurses and other
health care professionals. The book provides
students of these professions with vital
microbiology information that will enable them
to carry out their duties in an informed, safe,
and efficient manner and protect themselves
and their patients from infectious diseases.
WHAT IS MICROBIOLOGY?
• Microbiology is the study of microbes. With
only rare exceptions, individual microbes
can be observed only with the use of
various types of microscopes.
Microbes play significant roles in our lives, and
the following are a few of the many reasons to
take a microbiology course and to learn about
microbes:
We have, living on and in our bodies (e.g.,
on our skin and in our mouths and intestinal
tract), approximately 10 times as many
microbes as the total number of cells (i.e.,
epithelial cells, nerve cells, muscle cells)
that make up our bodies (10 trillion cells ×
10 = 100 trillion microbes).
• It has been estimated that perhaps as many as
500 to 1,000 different species of microbes are
known as our indigenous micro biota (or human
micro biome) and, for the most part, they are of
benefit to us.
For example, the indigenous microbiota inhibit
the growth of pathogens in those areas of the
body where they live by occupying space,
depleting the food supply, and secreting
materials (waste products, toxins, antibiotics,
etc.) that may prevent or reduce the growth of
pathogens.
Some of the microbes that colonize (inhabit) our
bodies are known as opportunistic pathogens
(or opportunists). Although these microbes
usually do not cause us any problems, they
have the potential to cause infections if they
gain access to a part of our anatomy where
they do not belong.
• For example, a bacterium called Escherichia
coli lives in our intestinal tracts. This
organism does not cause us any harm as
long as it remains in our intestinal tract, but
can cause disease if it gains access to our
urinary bladder, bloodstream, or a wound.
• Microbes are essential for life on this planet as
we know it. For example, some microbes
produce oxygen by the process known as
photosynthesis .
• Actually, microbes contribute more oxygen to our
atmosphere than do plants. Thus, organisms that
require oxygen—humans, for example—owe a
debt of gratitude to the algae and cyanobacteria
(a group of photosynthetic bacteria) that produce
oxygen.
• Many microbes are involved in the
decomposition of dead organisms and the waste
products of living organisms. Collectively, these
microbes are referred to as decomposers or
saprophytes.
• Saprophytes aid in fertilization by returning
inorganic nutrients to the soil. They break down
dead and dying organic materials (plants and
animals) into nitrates, phosphates, and other
chemicals necessary for the growth of plants.
• Some microbes are capable of decomposing
industrial wastes (oil spills, for example). Thus,
we can use microbes—genetically engineered
microbes, in some cases—to clean up the
environment. The use of microbes in this
manner is called bioremediation.
• Many microbes are involved in elemental
cycles, such as the carbon, nitrogen, oxygen,
sulfur, and phosphorous cycles.
VARIOUS CATEGORIES OF MICROBES
• The various categories of microbes are viruses,
bacteria, archaea, protozoa, and certain types of
algae and fungi
• Because most scientists do not consider viruses to
be living organisms, they are often referred to as
―acellular microbes‖ or ―infectious particles‖ rather
than microorganisms.
• Many microbes are essential in various food
and beverage industries, whereas others are
used to produce certain enzymes and
chemicals.
• The use of living organisms or their
derivatives to make or modify useful products
or processes is called biotechnology.
• For many years, microbes have been used
as ―cell models.‖ The more the scientists
learned about the structure and functions of
microbial cells, the more they learned about
cells in general.
• The intestinal bacterium E. coli is one of the
most studied of all microbes. By studying E.
coli, scientists have learned a great deal
about the composition and inner workings of
cells, including human cells.
Microbes cause two categories of diseases:
Infectious diseases - results when a pathogen
colonizes the body and subsequently causes
disease.
Microbial intoxication - results when a person
ingests a toxin (poisonous substance) that has
been produced by a microbe
FIRST MICROORGANISMS ON EARTH
• Fossils of primitive microbes (as many as 11
different types) found in ancient sandstone
formations in northwestern Australia date back
about 3.5 billion years ago. Candidates for the first
microbes on Earth are archaea and cyanobacteria
Cyanobacteria
Archaea
Brief History of Microbiology
Bacteria and protozoa were the first microbes to be
observed by humans. It then took about 200 years before a
connection was established between microbes and
infectious diseases.
Among the most significant events in the early history of
microbiology were the development of microscopes,
bacterial staining procedures, techniques that enabled
microorganisms to be cultured (grown) in the laboratory,
and steps that could be taken to prove that specific
microbes were responsible for causing specific infectious
diseases.
Spontaneous generation theory
The Greek philosopher Aristotle (384–322 BC) was
one of the earliest recorded scholars to articulate the
theory of spontaneous generation, the notion that life
can arise from nonliving matter.
Aristotle proposed that life arose from nonliving
material if the material contained pneuma (―vital
heat‖). As evidence, he noted several instances of the
appearance of animals from environments previously
devoid of such animals, such as the seemingly sudden
appearance of fish in a new puddle of water.1
DEVELOPMENT OF MICROBIOLOGY
1590: Hans and Zacharias Jansen (Dutch
lens grinders) mounted two lenses in a tube to
produce the first compound microscope
1660: Robert Hooke (1635-1703) compound
light microscope; discovered cells
Anton van Leeuwenhoek (1632–1723)
Not a trained scientist.
At various times in his
life, he was a fabric
merchant, a surveyor, a
wine assayer, and a
minor city official in
Delft, Holland.
―Father of Microbiology,‖
As a hobby, he ground tiny glass lenses, which he
mounted in small metal frames, thus creating what today
are known as single-lens microscopes or simple
microscopes. During his lifetime, he made more than
500 of these microscopes.
Apparently, Leeuwenhoek had an unquenchable curiosity,
as he used his microscopes to examine almost anything he
could get his hands on ,
examined scrapings from his teeth
water from ditches and ponds,
water in which he had soaked peppercorns, blood,
sperm, and even his own diarrheal stools.
In many of these specimens, he observed various
tiny living creatures, which he called
“animalcules.” He recorded his observations in
the form of letters, which he sent to the Royal
Society of London.
Leeuwenhoek’s letters finally convinced scientists
of the late 17th century of the existence of
microbes. He never speculated on their origin,
nor did he associate them with the cause of
disease.
1668: Francesco Redi (1626-1678). Redi was
an Italian physician who refuted the idea of
spontaneous generation by showing that rotting
meat carefully kept from flies will not
spontaneously produce maggots.
1745: John Needham (1713-1781). Needham,
an English clergyman, was an advocate for
spontaneous generation. He boiled chicken
broth, put it into a flask sealed it, and waited-
microorganisms grew.
Lazzaro Spallanzani (1729-1799). Spallanzani,
an Italian priest, suggested that
microorganisms had entered from the air after
the broth was boiled, but before it was sealed.
He placed broth in flask, sealed it, and then
boiled it. No organisms grew. Proponents of
spontaneous generation argued that air was
needed for spontaneous generation to occur.
1861: Louis Pasteur (1822-1895). Pasteur's experiment was
a variation of the methods of Needham and Spallanzani.
Air could enter the flask, but
airborne microorganisms could
not - they would settle by gravity
in the neck. No microorganisms
grew. When flask was tilted so
broth came into contact with
area where airborne particles
settled, the broth became
cloudy. Pasteur disproved the
theory of spontaneous
generation and showed
microorganisms are everywhere.
Proof that microbes cause
disease:
Louis Pasteur (1822–1895)
A French chemist, made
numerous contributions to
the newly emerging field of
microbiology, and, in fact,
his contributions are
considered by many
people to be the foundation
of the science of
microbiology and a
cornerstone of modern
medicine.
Contributions of Louis Pasteur
Fermentation - Pasteur discovered what occurs during
alcoholic fermentation . He also demonstrated that
different types of microbes produce different
fermentation products. For example, yeasts convert the
glucose in grapes to ethyl alcohol (ethanol) by
fermentation, but certain contaminating bacteria, such as
Acetobacter, convert glucose to acetic acid (vinegar) by
fermentation, thus ruining the taste of the wine.
Pasteur discovered forms of life that could exist
in the absence of oxygen. He introduced the
terms “aerobes” (organisms that require
oxygen) and “anaerobes” (organisms that do
not require oxygen).
Pasteurization - to kill microbes by heating liquids to
63°C to 65°C for 30 minutes or to 73°C to 75°C for 15
seconds. It should be noted that pasteurization does not
kill all of the microbes in liquids—just the pathogens.
Pasteur made significant contributions to the
―Germ theory of disease”—the theory that
specific microbes cause specific infectious
diseases.
Ex:
anthrax is caused by a specific
bacterium (Bacillus anthracis), whereas
tuberculosis is caused by a different
bacterium (Mycobacterium tuberculosis).
Pasteur developed vaccines to prevent chicken
cholera, anthrax, and swine erysipelas (a skin
disease). It was the development of these
vaccines that made him famous in France.
Before the vaccines, these diseases were
decimating chickens, sheep, cattle, and pigs in
that country—a serious economic problem.
Pasteur developed a vaccine to prevent rabies
in dogs and successfully used the vaccine to
treat human rabies.
Pasteur Institute was created in Paris in 1888.
- Became a clinic for rabies treatment, a
research center for infectious diseases, and
a teaching center.
1546: Girolamo Fracastoro (1478-1553) an Italian
physician was credited with the first written
allusions to the germ theory of disease. He
wrote about the "seeds of disease" which can
pass from one person to another.
1847: Ignaz Semmelweiss (1818-1865) was a
Hungarian physician who decided that doctors
in Vienna hospital were spreading childbed
fever while delivering babies He started forcing
doctors under his supervision to wash their
hands before touching patients.
1867: Joseph Lister (1827-1912) an English
physician developed a system of sterile surgery
designed to prevent microorganisms from
entering wounds; his patients had fewer
postoperative infections.
Robert Koch (1843–1910)
A German physician, made numerous
contributions to the science of microbiology.
Koch’s Postulates
Koch made many significant contributions to the
germ theory of disease. For example, he proved
that the anthrax bacillus (B. anthracis), which had
been discovered earlier by other scientists, was
truly the causative agent of anthrax. He
accomplished this using a series of scientific steps
that he and his colleagues had developed;
Koch discovered that B. anthracis produces
spores, capable of resisting adverse conditions.
Koch developed methods of fixing, staining, and
photographing bacteria.
Koch developed methods of cultivating bacteria
on solid media. One of Koch’s colleagues, R.J.
Petri, invented a flat glass dish (now known as a
Petri dish) in which to culture bacteria on solid
media.
Koch discovered the bacterium (M. tuberculosis)
that causes tuberculosis and the bacterium
(Vibrio cholerae) that causes cholera.
Koch’s work on tuberculin (a protein derived
from M. tuberculosis) ultimately led to the
development of a skin test valuable in
diagnosing tuberculosis.
CAREERS IN MICROBIOLOGY
Microbiologist - is a scientist who studies
microbes. He or she might have a
bachelor’s, master’s, or doctoral degree in
microbiology.
There are many career fields within the science
of microbiology. For example, a person may
specialize in the study of just one particular
category of microbes.
Bacteriologist is a scientist who specializes in
bacteriology —the study of the structures,
functions, and activities of bacteria.
Phycologist study the various types of algae
Protozoologists explore the area of
protozoology—the study of protozoa and their
activities.
Mycologists- those who specialize in the study of
fungi or Mycology
Virologist- those specialize in the study of
viruses and their effects on living cells of all
types or those specialize in virology .
Other career fields in microbiology pertain more
to applied microbiology, that is, how a
knowledge of microbiology can be applied to
different aspects of society, medicine, and
industry. The scope of microbiology has broad,
far-reaching effects on humans and their
environment.
Medical and Clinical Microbiology
The field of medical microbiology involves the
study of pathogens, the diseases they cause, and
the body’s defenses against disease.
This field is concerned with epidemiology,
transmission of pathogens, disease-prevention
measures, aseptic techniques, treatment of
infectious diseases, immunology, and the
production of vaccines to protect people and
animals against infectious diseases.
Branch of medical microbiology,
Clinical microbiology or diagnostic
microbiology, is concerned with the laboratory
diagnosis of infectious diseases of humans.
This is an excellent career field for individuals
with interests in laboratory sciences and
microbiology.
Thanks for listening
