INTRODUCTION TO
MICROBIOLOGY
LESSON OBJECTIVES
1 WHAT IS MICROBIOLOGY?
2 WHY STUDY MICROBIOLOGY?
3 FIRST MICROORGANISMS ON EARTH
4 EARLIEST KNOWN INFECTIOUS DISEASES
5 PIONEERS IN THE SCIENCE OF MICROBIOLOGY
6 CAREERS IN MICROBIOLOGY
MICRO- BIOLOGY
a prefix derived from the the scientific study of life
Greek word mikros, meaning and living organisms
"small" or "tiny"
WHAT IS MICROBIOLOGY
ALL ABOUT?
is the study of certain microscopic
nonliving entities as well as certain
living organisms, collectively called as
microbes
can be defined as the study of
microbes
WHAT IS MICROBIOLOGY
ALL ABOUT?
The two major categories of microbes
are called acellular microbes and
cellular microbes.
ACELLULAR
INFECTIOUS AGENTS
MICROBES
also called infectious
particles
include viruses and prions
CELLULAR
MICROORGANISMS
MICROBES
also called
microorganisms
include the less complex
procaryotes (archaea and
bacteria) and the more
complex eucaryotes
(algae, protozoa, and
fungi)
PATHOGENS
disease-causing microbes
only about 3% of known microbes
are pathogenic (“microbial enemies”)
NONPATHOGENS
microbes that do not cause disease
vast majority of known microbes
are nonpathogens
some nonpathogens are beneficial
(“microbial allies”) to us, whereas
others have no effect on us at all
OPPORTUNISTIC PATHOGENS
microbes that normally inhabit our bodies without
causing harm but can cause disease under certain
conditions.
they can cause infections if they enter parts of the
body where they don't belong; and,
attack when a person's immune system is
weakened, stressed, or debilitated by other diseases
or conditions.
WHY DO WE STUDY MICROBIOLOGY?
Although they are very small, microbes play significant roles in our lives.
Listed in the following slides are a few of the many reasons to take a
microbiology course and to learn about microbes:
WHY DO WE STUDY MICROBIOLOGY?
Indigenous Microflora
living on and in our bodies (e.g., on our skin and in our mouths and intes
tinal tract) is approximately 10 times as many microbes as the total
number of cells
these microbes are known as our indigenous microflora (or indigenous
microbiota)
they inhibit the growth of pathogens in those areas of the body where
they live by occupying space, depleting the food supply, and secreting
materials
WHY DO WE STUDY MICROBIOLOGY?
Photosynthetic Bacteria
microbes are essential for life on this planet as we know it with some
producing oxygen by the process known as photosynthesis
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
WHY DO WE STUDY MICROBIOLOGY?
Decomposers or Saprophytes
many microbes are involved in the decomposition of dead organisms
and the waste products of living organisms, collectively referred to as
decomposers or saprophytes
they aid in fertilization by breaking down dead and dying organic
materials and returning them as inorganic nutrients to the soil
WHY DO WE STUDY MICROBIOLOGY?
WHY DO WE STUDY MICROBIOLOGY?
WHY DO WE STUDY MICROBIOLOGY?
Bioremediation
some microbes are capable of decomposing industrial wastes (oil spills,
for example).
we can use microbes—genetically engineered microbes, in some cases—to
clean up after ourselves, called bioremediation
WHY DO WE STUDY MICROBIOLOGY?
Elemental Cycles
many microbes are involved in elemental cycles, such as the carbon,
nitrogen, oxygen, sulfur, and phosphorous cycles
knowledge of these microbes is important to farmers who practice crop
rotation to replenish nutrients in their fields and to gardeners who keep
compost pits as a source of natural fertilizer
the study of the relationships between microbes and the environment is
called microbial ecology
WHY DO WE STUDY MICROBIOLOGY?
Food Chains
algae and bacteria serve as food for tiny animals. Then, larger animals eat
the smaller creatures, and so on. Thus, microbes serve as important links
in food chains
microscopic organisms in the ocean, collectively referred to as plankton,
serve as the starting point of many food chains.
tiny marine plants and algae are called phytoplankton, whereas tiny
marine animals are called zooplankton
WHY DO WE STUDY MICROBIOLOGY?
Digestion and Production of Subtances
some microbes live in the intestinal tracts of animals, where they aid in
the digestion of food and, in some cases, produce substances that are
of value to the host animal
the E. coli bacteria that live in the human intestinal tract produce
vitamins K and B1, which are absorbed and used by the human body
termites have cellulose-eating protozoa in their intestinal tracts that
break down the wood that the termites consume into smaller molecules
that the termites can use as nutrients
WHY DO WE STUDY MICROBIOLOGY?
WHY DO WE STUDY MICROBIOLOGY?
WHY DO WE STUDY MICROBIOLOGY?
Biotechnology
many microbes are essential in various food and bever age industries,
whereas others are used to produce certain enzymes and chemicals
some bacteria and fungi produce antibiotics that are used to treat
patients with infectious diseases by effectively killing or inhibiting the
growth of other microbes.
the use of living organisms or their derivatives to make or modify useful
products or processes is called biotechnology
WHY DO WE STUDY MICROBIOLOGY?
Genetic Engeneering
microbiologists have engineered bacteria and yeasts to produce a
variety of useful substances, such as insulin, various types of growth
hormones, interferons, and materials for use as vaccines
a gene or genes from one organism (e.g., from a bacterium, a
human, an animal, or a plant) is/are inserted into a bacterial or yeast
cell; the cell that receives a new gene can now produce whatever
product is coded for by that gene; so too can all of the cells that arise
from the original cell
WHY DO WE STUDY MICROBIOLOGY?
Cell Models
microbes have been used as “cell models”; the more that 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;
scientists have learned a great deal about the composition and inner
workings of cells, including human cells
WHY DO WE STUDY MICROBIOLOGY?
Diseases
microbes cause two categories of diseases: infectious diseases and
microbial intoxications
infectious disease - a pathogen colonizes the body and subsequently
causes disease
microbial intoxication - a person ingests a toxin (poisonous substance)
that has been produced by a microbe
worldwide, infectious diseases cause about 50,000 deaths per day, with
the majority of deaths occuring in developing countries
WHY DO WE STUDY MICROBIOLOGY?
FIRST MICROORGANISMS ON EARTH
scientists tell us that the Earth was formed about 4.5 billion years ago and,
for the first 800 million to 1 billion years of Earth’s existence, there was no
life on this planet
fossils of primitive microbes (as many as 11 differ ent types) found in
ancient rock formations in northwestern Australia date back to about 3.5
billion years ago
candidates for the first microbes on Earth are archaea and cyanobacteria
EARLIEST KNOWN INFECTIOUS DISEASES
human pathogens have existed for thousands of years because
damage caused by them has been observed in the bones and internal
organs of mummies and early human fossils
bacterial diseases, such as tuberculosis and syphilis, and parasitic worm
infections, such as schistosomiasis, dracunculiasis (guinea worm
infection), and tapeworm infections, have been around for a very long
time
EARLIEST KNOWN INFECTIOUS DISEASES
3180 BC: The earliest account of a "pestilence" in Egypt, possibly the first
recorded epidemic
1900 BC: Near the end of the Trojan War, the Greek army experienced an
epidemic, likely bubonic plague
1500 BC: The Ebers papyrus, describing epidemic fevers, was written and
later discovered in Thebes, Egypt
1122 BC: A disease thought to be smallpox occurred in China
790, 710, 640 BC: Epidemics of plague in Rome
430 BC: Epidemics of plague in Greece
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Microbial Observations & Advances in Microbiology:
Bacteria and protozoa were the first microbes observed by humans.
It took about 200 years to establish a connection between microbes and
infectious diseases.
Significant events in early microbiology include:
Development of microscopes
Bacterial staining procedures
Techniques to culture microorganisms in the laboratory
Proof that specific microbes cause specific infectious diseases
Over the past 400 years, numerous individuals have contributed to our
understanding of microbes, with three early microbiologists highlighted.
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Anton van Leeuwenhoek is often referred to
as the "Father of Microbiology," "Father
of Bacteriology," and "Father of
Protozoology"
He was the first person to see live
bacteria and protozoa, calling them as
“animalcules” (tiny living creatures).
Leeuwenhoek ground tiny glass lenses as a
hobby, creating over 500 single-lens
ANTON VAN LEEUWENHOEK (1632–1723) microscopes that magnified objects 200-
300 times.
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
His work laid the foundation for
modern microbiology and greatly
advanced our understanding of
microorganisms.
He convinced scientists of the late 17th
century of the existence of microbes.
He did not speculate on their origins or
link them to diseases. Such connections
were later established by Louis Pasteur
ANTON VAN LEEUWENHOEK (1632–1723)
and Robert Koch in the late 19th century.
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Leeuwenhoek’s groundbreaking work
pioneered a discovery, the hidden world
of microscopic life forms, impacting
our understanding of disease and biology
profoundly.
ANTON VAN LEEUWENHOEK (1632–1723)
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
After scientists acknowledged the existence of microscopic creatures, they
began speculating on their origins.
Many believed in the theory of spontaneous generation (abiogenesis),
which suggested life could develop from nonliving materials. This
theory was debated and tested from 1650 to 1850.
Louis Pasteur and John Tyndall eventually disproved spontaneous
generation, proving instead that life arises from preexisting life, known
as the theory of biogenesis, first proposed by Rudolf Virchow in 1858.
The theory of biogenesis does not address the ultimate origin of life, a
ANTON VAN LEEUWENHOEK (1632–1723)
topic still debated.
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Alcoholic Fermentation: Discovered
what happens during fermentation and
how different microbes produce different
products (e.g., yeast converting glucose to
ethanol, bacteria converting glucose to
acetic acid).
Disproving Spontaneous Generation:
Through experiments, he debunked the
theory of spontaneous generation.
LOUIS PASTEUR (1822–1895)
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Anaerobes and Aerobes: Identified life
forms that can exist without oxygen and
introduced the terms "aerobes" and
"anaerobes."
Pasteurization: Developed the
pasteurization process to kill microbes
causing spoilage in liquids, such as wine
and milk.
LOUIS PASTEUR (1822–1895)
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Silkworm Disease: Discovered the
infectious agents causing silkworm
diseases and found ways to prevent
them.
Germ Theory of Disease: Contributed
significantly to the germ theory, proving
that specific microbes cause specific
diseases.
LOUIS PASTEUR (1822–1895)
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Hospital Practices: Advocated for
changes in hospital practices to reduce
disease spread.
Vaccines: Developed vaccines for chicken
cholera, anthrax, swine erysipelas, and
rabies.
LOUIS PASTEUR (1822–1895)
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
The Pasteur Institute was established in
Paris in 1888 to honor his work, focusing
on rabies treatment, infectious disease
research, and teaching. Scientists trained
under Pasteur made further important
discoveries, forming a global network of
Pasteur Institutes.
LOUIS PASTEUR (1822–1895)
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Germ Theory of Disease: Proved that
Bacillus anthracis causes anthrax using
scientific steps later known as Koch's
Postulates.
Spore Formation: Discovered that
Bacillus anthracis produces spores that
can resist adverse conditions.
Bacterial Methods: Developed methods
for fixing, staining, and photographing
ROBERT KOCH (1843–1910)
bacteria.
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Cultivating Bacteria: Created methods
for cultivating bacteria on solid media,
leading to the invention of the Petri dish
and the use of agar as a solidifying
agent, enabling the growth of pure
cultures.
Disease Discovery: Identified
Mycobacterium tuberculosis as the cause
of tuberculosis and Vibrio cholerae as the
ROBERT KOCH (1843–1910)
cause of cholera.
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Koch’s Postulates
Koch’s Postulates: Established by Robert
Koch and colleagues in the mid- to late-
1800s, published in 1884, to prove that a
specific microbe causes a specific
infectious disease (germ theory of
disease). The postulates include:
ROBERT KOCH (1843–1910)
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Koch’s Postulates
The postulates include:
A particular microbe must be found in all
cases of the disease and not in healthy
animals or humans.
The microbe must be isolated from the
diseased animal or human and grown in
pure culture in the laboratory.
ROBERT KOCH (1843–1910)
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Koch’s Postulates
The postulates include:
The same disease must be produced
when microbes from the pure culture are
inoculated into healthy, susceptible
laboratory animals.
The same microbe must be recovered
from the experimentally infected animals
and grown again in pure culture.
ROBERT KOCH (1843–1910)
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
ROBERT KOCH (1843–1910)
PIONEERS IN THE SCIENCE OF MICROBIOLOGY
Koch’s Postulates were pivotal in proving
the germ theory of disease and
advancing microbiology by emphasizing
the importance of laboratory culture and
identification of microbes.
Not all diseases are caused by
microbes; some are result from dietary
de ficiencies, while others are inherited
because of an abnormality in the
ROBERT KOCH (1843–1910)
chromosomes.
CAREERS IN MICROBIOLOGY
A microbiologist studies microbes and may hold a bachelor's, master's, or doctoral
degree in microbiology. There are various specializations within the field:
Bacteriologist: Studies the structure, functions, and activities of bacteria.
Phycologist (Algologist): Studies various types of algae.
Protozoologist: Focuses on the study of protozoa.
Mycologist: Specializes in the study of fungi.
Virologist: Studies viruses and their effects on living cells, and may also work
as a genetic engineer, transferring DNA between cell types. Virologists may also
study prions and viroids, smaller than viruses.
Microbiologists can also work in applied fields, applying their knowledge to society,
medicine, and industry, with broad impacts on humans and the environment.
CAREERS IN MICROBIOLOGY
Medical Microbiology
Focuses on the study of pathogens, the diseases they cause, and the body’s defenses
against these diseases. Key areas include:
Epidemiology
Transmission of pathogens
Disease prevention measures
Aseptic techniques
Treatment of infectious diseases
Immunology
Vaccine production
The field has contributed to the near-eradication of diseases like smallpox and polio,
the safety of modern surgery, and the successful treatment of infectious diseases.
CAREERS IN MICROBIOLOGY
Clinical Microbiology
A subfield, Clinical Microbiology (Diagnostic Microbiology), deals with the laboratory
diagnosis of infectious diseases in humans. This field is ideal for those interested in
laboratory sciences and microbiology, providing crucial support for the medical
industry.
