1. Fundamentals of Microbiology
Development of Microbiology
Significance of Studying Microbiology
Prokaryotic and Eukaryotic cell structure
Bacterial cell Structure
Bacterial Nutrition and Growth
• Upon completion of this unit of instruction, the student will be able
Discuss the historical background of Microbiology
Discuss the significance of studying Microbiology
Classify medically-significant bacteria according to their
phenotype and genotype
Identify external and internal structural components of bacteria
Discuss bacterial genetics
CHAPTER I: INTRODUCTION
• is a subject which deals with living organisms that are
individually too small to be seen with the naked eye.
• It considers the microscopic forms of life and deals about their
• Reproduction and physiology
• participation in the process of nature
• helpful and harmful relationship with other living things
• significance in science and industry
Subdivisions of Microbiology
Sub divisions of microbiology
Bacteriology – which deals with bacteria
Mycology- which deals with fungi
Phycology - Which deals with Algae.
Protozoology – which deals with Protozoa.
Helminthology –which deals with worms
Virology -studies about viruses
It involves the study of pathogens, the disease caused by them,
and the body’s defenses against disease.
• It is also concerned with
• Epidemiology, transmission of pathogens
• disease prevention measures, and
• aseptic techniques and treatment of infectious diseases
• Immunology and production of vaccines.
Man kind has always been affected by diseases which were
originally believed to be visitations by the gods and meant to punish
• father of medicine
• observed that ill health resulted due to changes in air, winds,
water, climate, food, nature of soil and habits of people.
• Varro (117-26 BC) : formulated a theory that
• diseases were caused by animated particles invisible to
• which were carried in the air and acquired via the mouth
and nose into the body.
• Fracastoro (1478–1553 G.c):
proposed that the agent of communicable diseases were
Could be transmitted by direct contact with humans and
Indirectly by objects
But no proofs due to lack of experimental evidence.
• Antony van leeuwehoek ( 1632-1723 G.c)
Father of microbiology, observed “animalcules” using
simple microscope with one lense.
He was the first who properly described the different
shapes of bacteria.
Question raised - where did they originate?
Leeuwenhoek was not concerned about the origin of Mos.
many other scientists were searching for an explanation for
spontaneous appearance of living things from
fermenting grains and infected wounds
• On the bases of this observation, two major theories
1. Theory of Abiogenesis
2. Theory of Biogenesis
Theory of Abiogenesis:
• Theory of Abiogenesis:
• deals with the theory of spontaneous generation
• stating that living things originated “spontaneously” from non-
• Aristotle (384-322 BC):
• The founder of a theory spontaneous generation.
• He observed spontaneous existence of fishes from dried ponds,
when the pond was filled with rain.
Theory of Biogenesis:
• Theory of Biogenesis:
• States that life comes from pre-existing life.
• Francesco Redi (1626-1697):
• He is the scientist who first tried to set an experiment to
disprove spontaneous generation.
• Utilized jars containing meat.
• Some were covered, some were not.
Theory of Biogenesis…
• He observed that the flies laid eggs on uncovered jar from
which the maggots developed but not from covered jars.
• He said maggots did not developed from meat but from flies
• Results not accepted for microscopic organisms.
• Introduced experimental procedure to disproof spontaneous
• The controversy on spontaneous generation took 200 years.
Theories of …
• John Needham (1749)-Utilized infusion broth prepared by
boiling meat, grain, etc. to extract nutrients.
• Lazzaro Spallanzani (1776)- used boiled broth
• Turbidity indicated growth.
• Louis pasture (1822- 1895) :
• He was the scientist who disproved the theory of abiogenesis
once and for all.
• In his experiment he filtered air through cotton plug.
• He placed plug in infusion broth, broth became cloudy -
organisms present in the air.
• He designed
a large curved flask or
pasture goose neck flask and placed a sterile infusion
• Flasks remained sterile unless tilted or neck broken.
Luis Pasteur’s experiment
In ‘A’ air freely moved through the tube, but dust particles were trapped in the curved portion of
the flask. And no microbial growth was observed
Therefore, Pasteur proved that microorganisms entered to the
broth with the air and micro organisms did not evolve
Other major contribution of Louis Pasteur
1. Microbial theory of fermentation
2. Principles and practices of sterilization and
3. Control of disease of silk worm
4. Development of vaccines against anthrax and rabies
5. Discovery of streptococci.
The Germ Theory of diseases
• Robert Koch
• He established an experimental procedure to prove the germ
theory of disease in 1876.
• The theory states that specific disease is caused by specific
• The scientific procedure is known as Koch’s Postulate.
proof of germ theory of disease.
A Mo can be accepted as a causative agent of an infectious
disease only if the following conditions are satisfied.
1. The specific causative agent must be found in every case of
the disease but absent from health organism.
2. The suspected micro-organism must be isolated and grown
in pure culture.
3. Inoculation of a sample of the culture into a healthy
organism, susceptible animal must produce the same disease.
Exceptions to Koch’s postulate
• Many healthy people carry pathogens but do not exhibit symptoms
of the disease.
• Some microbes are very difficult or impossible to grow in vitro (in
the laboratory) in artificial media. E.g. Treponema pallidum.
• Many pathogens are species specific. E.g. Brucella abortus cause
abortion in animals but not in humans.
• Certain diseases develop only when an opportunistic pathogen
invades imuno-compromised host.
Major achievements of Robert Koch
• use of solid medium in bacteriology
• Discovery of causative agents of
tuberculosis and cholera
• Koch’s postulate
• Luis Pasture has also developed the germ
theory of diseases.
Significance of Studying Microbiology
• WHY STUDY MICROBIOLOGY?
• MOs have a tremendous impact on all life
• They are physical and chemical makeup of our planet.
• Microorganisms have a close association with humans.
• They are in us, on us, and nearly everywhere around us.
• One reason for studying microbiology is that MOs are part of the
human environment and are therefore important to human health.
• MOs are essential to the web of life in every environment.
capture energy from sunlight
decompose dead organisms, waste material, and even some
kinds of industrial wastes.
make nitrogen available to plants
maintain the balance of nature
synthesize antibiotics, vaccines
are the major tools of genetic engineering
certain microbes cause disease.
Studying microbiology is provides insight into life processes in all
• In general, Microorganisms are part of the human environment
and are therefore important to human health and activities.
• The study of microorganisms provides insight into life
processes in all forms of life.