1. HISTORY AND SCOPE OF
MICROBIOLOGY
Dr. Saji Mariam George
Associate Professor,
Assumption College, Autonomous
Changanacherry

2. MICROBIOLOGY
 Study of Microbes –
too small to be
seen with naked
eye.
 Less than 1mm in
diameter.
 Some are visible to
the naked eye –
e.g.Bacterium
Epulopiscium,
filamentous algae,
bread mould, mush
rooms etc.
Image : https://alchetron.com/Epulopiscium-fishelsoni

3. MICROBES
 Extremely diverse group
• Bacteria ( Study of Bacteria -Bacteriology)
• Algae( Study of Algae - Phycology)
• Fungi ( Study of Fungi - Mycology)
• Viruses (Study of Viruses - Virology)
• Protozoa ( Study of Protozoa - Protozoology)

4. TYPES OF MICROBIOLOGY
 Theoretical or Pure Microbiology
 Practical or Applied Microbiology

5. THEORETICAL(PURE) MICROBIOLOGY
• Study of occurrence
• Form
• Structure
• Classification
• Physiology
• Reproduction
• Heredity
• Variation and Evolution of microbes

6. APPLIED MICROBIOLOGY
Exploitation of beneficial microbes
Control the activities of harmful microbes
Types:
• Medical Microbiology – Study of role of
microbes in human & animal diseases.
• Agricultural Microbiology – Role of microbes
in plant diseases, soil fertility and spoilage of
agricultural products.

7. • Industrial Microbiology - Utilisation of
microbes for the production of alcoholic
beverages, antibiotics, amino acids, organic
acids –acetic acid, lactic acid, citric acid etc.
• Food Microbiology – Role of microbes in
food spoilage, their prevention and to
increase the shelf life of various food
products ; production of cheese, butter,
fermented milk etc.

8. HISTORY OF MICROBIOLOGY
• Microbes – discovered
in the late 17th century.
• First observed by Anton
van Leeuwenhoek –
Father of Microbiology.
• A Dutch draper - Hobby
was lens grinding and
microscope making.
• Made 550 crude single
lens microscopes with
magnification of 50x –
300 x.

9. Anton van Leeuwenhoek’s
Microscope
Images: https://commons.wikimedia.org/
https://yalepress.tumblr.com/

10. Anton van Leeuwenhoek’s observation of microbes
Image: https://delftschoolmicrobiology.weblog.tudelft.nl/

11. • Leeuwenhoek examined rain water, saliva,
pepper decoctions, cork, leaves of plants ,
seminal fluid, scrappings of teeth etc.
• Portrayed several microorganisms and called
them ‘Animal cules’.
• Conveyed his findings in a series of letters to
the British Royal Society, London during the
mid 1670’s.

12. • Leeuwenhoek outlined the structural details
of Paramecium, Amoeba, certain filamentous
fungi, algae , bacteria etc.
• Scientists considered microbes only as
‘Curiosities of Nature’.
• Controversy regarding Spontaneous
generation (Abiogenesis) drew scientists to
explore the origin and nature of living things.

13. • Spontaneous generation(Abiogenesis)
A belief in ancient times that living organisms
could develop from non – living matter.
• Theory of Biogenesis – Living organisms arise
only from preexisting organisms.

14. Experiments to disprove Abiogenesis
Redi’s Experiment (1688):
(Francesco Redi 1626
– 1697, Italian Physician)
Carried out a series of
experiments on decaying
meat and its ability to
produce maggots
spontaneously.
Image
https://fineartamerica.com/fe

15. Redi placed meat in 3 jars
Jar 1 : Left open.
Flies laid eggs on meat -
which developed into
maggots .
Image http://faculty.sdmiramar.edu/

16. Jar-2 : Covered with netting
• Flies laid eggs on the
netting – developed into
maggots on the netting.
• Image http://faculty.sdmiramar.edu/

17. Jar-3 : Sealed
• No maggots developed
on meat.
• This experiment proved
that the maggots
developed from fly
eggs , not from meat .
• Thus Redi disproved
the theory of
spontaneous
generation
(Abiogenesis). Image http://faculty.sdmiramar.edu/

18. Experiment of Louis Pasteur
• Experiments in Swan –neck flasks - Disproved
the theory of Abiogenesis.
• Boiled the flasks of broth – then left them open
to the air and any of ‘life force’ — Life appears.
• The broth in Swan –neck flasks when left open
in air and any of ‘life force’ — no life appears
because the S- shaped curvature trapped the
microbes.

19. Image https://courses.lumenlearning.com/

20. • In 1800s, the scientists
believed that the infectious
diseases were spread by an
entity ‘miasms’- an altered
chemical quality of
atmosphere.
• Agostino Bassi (1773 –
1856) in 1835
demonstrated that a silk
worm disease was due to a
fungal infection – the first
report that a
microorganism could cause
disease.
Image: https://sciencecommunication425.wordpress.com/2

21. • Edward Jenner in
1796, had used
vaccination with
materials from cow
pox lesions to
protect people
against small pox.
Edward Jenner
Image : https://www.theschoolrun.com/

22. 1860 – 1910 : Golden age of
Microbiology
• Many research works were
conducted by Louis Pasteur
(1822 – 1895), Robert
Koch(1843 – 1910) and
others.
• Many branches of
Microbiology were
established.
Robert Koch
Image : https://en.wikipedia.org/

23. • A series of discoveries , mostly
involving identification of
agents of diseases.
• Developed an awareness that
infectious diseases were
caused by microorganisms and
the chain of transmission could
be broken → led to sterilization
practices in hospitals (Lister,
1867), pasteurization of milk,
purification of water, control of
insects, care in the preparation
of food for consumption etc.
Joseph Lister
Image : https://www.wired.com/

24. • Construction of a
bacterial filter by
Charles
Chamberland
(1884) made
possible the
discovery of
viruses and their
role in diseases.
Image : https://en.wikipedia.org/

25. • Dmitri Iwanowski
(1892) discovered
Tobacco Mosaic
Virus (TMV) – the
first viral
pathogen studied.
Image: https://en.wikipedia.org/

26. • Microbiology contributed
significantly to the
development of
Biochemistry – the
discovery of cell free
alcoholic fermentation by
Buchner(1897) provided
the key to chemical
analysis of energy yielding
processes. Image : https://en.wikipedia.org/

27. Contributions of Louis Pasteur-
Father of Industrial Microbiology
• Put an end to the theory
of Abiogenesis.
• First demonstrated that
air contain microbes.
• Discovered anaerobic life.
• Introduced the terms
aerobic and anaerobic.
• Established the Germ
theory of fermentation-
chemical changes like
fermentation are vital
processes brought about
by the activity of microbes
like yeasts and bacteria.
Image https://www.biography.com/scientist/louis-pasteur

28. • Established germ theory of disease –
microorganisms are responsible for infectious
diseases.
• Developed various methods of sterilization-
steam sterilization, hot air oven, autoclave.
• Coined the term vaccine.
• Developed vaccines for anthrax and rabies.

29. Contributions of F.J. Cohn
• Discovered binary
fission – the common
method of
multiplication in
bacteria.
• Discovered endospores
– certain bacteria form
extremely resistant
spores – Bacillus
subtilis, Clostridium
botulinum etc.
Image : https://en.wikipedia.org/

30. Contributions of Robert Koch
(1843 – 1910)
Father of Medical
Microbiology
• First to relate a specific
organism to a specific
disease – the
bacterium Bacillus
anthracis causes
anthrax.
• Also discovered Bacillus
of tuberculosis
(Mycobacterium
tuberculosis ) and the
Cholera vibrio.
Image : https://en.wikipedia.org

31. KOCH’S POSTULATES
• Robert Koch developed a series of
procedures by which a specific organism
could be related to a specific disease. These
steps are called Koch’s postulates.
i) The microorganism must be present in every
case of the disease but absent from healthy
organisms.
ii) The suspected microorganism must be
isolated and grown in a pure culture.

32. iii) The same disease must result when the
isolated microorganism is inoculated into a
healthy host.
iv) The same micro organism must be isolated
again from the diseased host.
By these procedures, a specific organism could
be related to a specific disease.
• Also developed many staining methods for
bacteria.

33. • Developed pure culture techniques
• Use of solid culture medium to grow
bacteria.

34. • In the last decade of the 19 th century,
microbiologist’s interests were concentrated on
the role of microbes as agents of infectious
diseases.
• Many of the important pathogenic organisms
have been discovered and their casual roles
established.
• The students of Pasteur, Koch and others
discovered in rapid succession a group of
bacteria capable of causing specific diseases ,
techniques and laboratory procedures.

35. • During the last decade of the
19th century, Microbiology
became an established
discipline with a distinct set of
concepts and techniques.
• During the early part of 20 th
century, Microbiology
developed independently of
other biological disciplines.
• Discovery of Electron
microscope (1934) , Tissue
culture technique etc.
Ernst Ruska & Max Knoll
Electron microscope
Image : https://i.pinimg.com/

36. • Development of drugs or
chemicals which could
kill infectious agents
while being non-toxic to
the host.
• In 1929 ,Sir Alexander
Fleming discovered the
antibiotic Penicillin from
Penicillium notatum,
which destroys
Staphylococci – the first
antibiotic produced from
microorganisms.
Many antibiotics are
produced from microbes. Image : https://www.tbat.co.uk/

37. • Microbiology established a
closer relationship with other
disciplines in 1940s.
• The first important
connection between Genetics
and Microbiology is the work
of Beadle and Tatum (1941).
They succeeded in isolating
biochemical mutants in
Neurospora crassa → one
gene – one enzyme
hypothesis.
Use of microbes to produce
valuable products→Industrial
Microbiology.
Image : https://bacterialsex.com/

38. • Development of rDNA technology (Gene
cloning or Genetic Engineering).
• Genetically modified microbes that can be
used as factory cells for the synthesis of
valuable pharmaceutical products like human
insulin, hormones, vaccines etc.

39. • Space Microbiology ( a branch of Exobiology-
investigating the possibility of extraterrestrial
life and the effects of extraterrestrial
environments on living organisms from the
earth. ) investigates the possibility of using
microbes as sources of food and oxygen.

40. Modern Microbiology is a well
developed discipline with established
concepts and techniques.

41. SCOPE OF MICROBIOLOGY
Many microbiologists focus on a specific group
of microorganisms.
• Virologists – on Viruses
• Bacteriologists – on Bacteria
• Phycologists – on Algae
• Mycologists – on Fungi
• Protozoologists –on Protozoa.

42. Different fields :
• Microbial Morphology
• Microbial Physiology
• Microbial Cytology
• Microbial Ecology
• Microbial Genetics & Molecular Biology
• Microbial Taxonomy
• Medical Microbiology

43. • Public health Microbiology
• Food Microbiology
• Dairy Microbiology
• Immunology

44. Microbes - Extremely useful as experimental
materials.
• Simple
• Grow rapidly
• Can culture in large quantities in test tubes,
flasks, require less space and maintenance
than large plants and animals.
• Easy – to – work –with material for studying
complex processes of metabolism.

45. • Metabolic processes – similar to higher plants
and animals
• Microbes can be used to study synthesis of
antibiotics ,toxins, energy production,
survival mechanism in harsh environmental
conditions, microbial nitrogen fixation etc.

46. THANK YOU