Introduction of microbiology

Introduction to the science of microbiology


• Biogenesis and spontaneous generation

• Discovery of microscope

• Louis Pasteur and his contributions

• Robert Koch and his contributions

• Introduction of aseptic methods

• Alexander Flemming and discovery of penicilllin

Learning objectives

At the end of this lecture student will be able to

• Outline the developments in microbiology

• Describe the contributions made by notable microbiologists

• Explain the difference between biogenesis and abiogenesis

• List the Koch postulates


• The study of living organisms that are too small for us to
see without a microscope – Microbes or Microorganisms

• Form the basis for all life on earth

• For nearly three quarters of the history of earth,
microbes were the only living things on earth


• Microorganism: refers to any organism that is too small to
be seen by the unaided eye

• It also includes some macroscopic forms like some fungi
and most of the algae

• Most microorganisms are unicellular

• If multicellular, they lack highly differentiated tissues
and organs

Origin of
microbial life on earth

• About 3.5 billion years ago, fossil evidence of microbes

• Some of the oldest cells on Earth are single-cell
organisms called archaea and bacteria. 

• Some began making their own food using carbon dioxide in
the atmosphere and energy they harvested from the sun. 

• This process produced enough oxygen to change Earth’s

• New oxygen-breathing life forms came onto the scene

History of

• Ancient Egyptians develop method of embalming

• Ancient Romans develop ideas about contagious particles

600 A.D Mayans
make fermented beverage from cacao

1348 A.D Black
Kills 1/3 of European population

1590 Janssen
develops compound microscope

1665 Robert Hooke
views cork through the microscope, coins the term ‘cell’

1668 Franscesco
performs the first documented controlled scientific experiments

– Covers meat with cheese cloth, and leaves other pieces of
meet uncovered. 

– Uncovered meat, exposed to flies, develops maggots. 

– Covered meat does not develop maggots. 

– Redi concludes that adult flies are necessary for the
production of maggots. 

– This is the first major blow to the theory of spontaneous

1674 Anton von
becomes first person to view living microorganisms.  This marks the beginning of Microbiology.

• 1735 Linnaeus
develops a taxonomy and a naming system binomial nomenclature) for organisms.

• 1745 John Needham
shows that boiled broth that cools down overnight becomes richly contaminated
with microorganisms. He forcefully argues the microbes must be borne from the broth.
He publishes a formal presentation of the Theory of Spontaneous Generation.

Theory of
spontaneous generation

• Spontaneous generation, an obsolete theory that states
that living organisms can originate from inanimate objects

• Dust creates fleas

• Maggots arise from rotting meat 

• Bread or wheat left in a dark corner produces mice

• 1767 Lazzaro
performs experiments with boiled and unboiled gravy. 

– He shows that boiled gravy will only spoil if exposed to

– He concludes that spontaneous generation cannot be

• 1798 Edward Jenner
performs the first vaccinations against smallpox. 

• He collects the pus from cowpox blisters on the hands of

• He contaminates a lance with this pus and then cuts the
skin of children.

1835 Agostino Bassi
proves that a fungus is the cause of silkworm disease.

• 1840 Ignaz
puts forth the revolutionary idea that   physicians should wash their hands when
assisting in childbirth.

• 1854 John Snow
identifies contaminated water as the cause of a cholera epidemic in England

• 1857 Louis Pasteur determines that
yeast cause fermentation of wine and develops the process of pasteurization
that saves the French wine industry. 

• This marks the beginning of the Golden Age of

period of explosive growth of knowledge of microbes (1857-1914).

• 1861 Louis Pasteur provides the final disproof of the
theory of spontaneous generation. 

• He maintains boiled broth in a swannecked flask, open to the
air, for many days without contamination.

• 1861 Louis Pasteur,
studying fermentation by yeast, coins the terms ‘aerobic’ and ‘anaerobic’

• 1866 Given the discovery of microscopic organisms, Ernst
Haeckel proposes a third Kingdom of Life: The Protista.

1867 Joseph Lister
uses phenol (carbolic acid) to treat surgical wounds. This reduced infection
from surgery dramatically and served as proof that surgical infections are
caused by microorganisms.

• 1876 Robert Koch,
studying the disease, anthrax, validates the Germ Theory of Disease–the idea
that diseases are caused by infectious agents (not by other forces such as evil

• This is also the first use of the rigorous steps in
pathogen identification known as Koch’s Postulates.

• 1879 Neisser
identifies the causative agent of gonorrhea (Neisseria gonorrhoeae).

• This may be the first case where a microbe is implicated
as the cause of a chronic disease.

• 1880 Pasteur
develops a vaccine for chicken cholera. 
This is the first attenuated vaccine.

• 1881 Koch
develops the concept of achieving pure cultures using solid media.

• 1882 Hess’
working in Koch’s lab, develops agar as a solid medium.

• 1882 Koch
identifies Mycobacterium tuberculosis as the causative agent of tuberculosis.

• 1883 Koch
identifies Vibrio cholerae as the causative agent of cholera.

• 1884 Koch
formalizes Koch’s Postulates- -the set of steps required to identify the
causative agent of a disease.


1. Bacteria can be found in all people with the disease

2. Bacteria can be isolated from the infected site

3. The pure culture inoculated into a susceptible individual
produces the symptom of disease

4. The same bacterium can be re-isolated from the intentionally
infected animal or human

• 1884 Hans Christian
develops the Gram Stain

• 1884 Escherich
identifies Escherichia coli

• 1884 Elie
describes phagocytosis (ingestion of solid materials by cells)

• 1885 Pasteur
develops a vaccine for rabies

• 1887 Petri
develops the petri plate for use with solid culture media

• 1929 Alexander
discovers the first antibiotic, penicillin.

• Fleming makes this discovery by

• He is searching for antimicrobial
chemicals and uses Staphylococcus cultures to test these chemicals. 

• He leaves some of these bacterial
cultures on the lab bench when he goes on vacation. 

• Upon returning, he sees that some
of his cultures are contaminated with a fungus called Penicillium. 

• He notices that there are no
bacteria growing near Penicillium.


• Microorganism: refers to any organism that is too small to
be seen by the unaided eye

• Microbiology is the study of microorganisms

• Anton von Leeuwenhoek becomes first person to view living

• Edward Jenner – small pox vaccine

• Robert Koch – laboratory cultivation of organisms, Koch

• Pasteur – theory of biogenesis, rabies and anthrax
vaccine, pasteurization

• Hans Christian Gram develops the Gram Stain

• Alexander Fleming discovers the first antibiotic,

• 1857 Pasteur-Fermentation

• 1861 Pasteur-Disproved spontaneous generation

• 1864 Pasteur-Pasteurization

• 1867 Lister-Aseptic surgery

• 1876 ‘Koch-Germ theory of disease

• 1879 Neisser-Neisseria gonorrhoeae

• 1881 ‘Koch-Pure cultures; Finley-Yellow fever

• 1882 ‘ Koch-Mycobacterium tuberculosis; Hess-Agar (solid)

• 1883 ‘ Koch-Vibrio cholerae

• 1884 ‘Metchnikoff-Phagocytosis; Gram-Gram’s staining
procedure; Escherich-Escherichia coli

• 1887 Petri-Petri dish

• 1889 Kitasato-Clostridium tetani

• 1890 Von Behring-Diphtheria antitoxin; ‘ Ehrlich-Theory of

• 1892 Winogradsky-Sullur cycle

• 1898 Shiga-Shigella dysenteriae

• 1908 Ehrlich-Syphilis; Chagas-Trypanosoma cruzi

• 1911 Rous-Tumor-causing virus (1966 Nobel Prize)

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