This section includes the history of microbiology.

1. What time is it?
What is today’s date?
Inventor of watch:Peter Henlein

2. History of medical microbiology
Objectives: after studying this class students will be able to;
1. Define microbes
2. Explain the theory of spontaneous generation
3. Enlist the contributions of Anton Van Leeuwenhoek
4. Enlist the contributions of Louis Pasteur
5. Enlist the contributions of Robert Koch
6. Explain how the life originated in earth
7. Enlist the major inventions in microbiology done by different
scientists
8. Describe law of attenuation
9. Enlist and explain Koch’s Postulates
10. Explain how the first antibiotic penicillin was discovered.

3. Contd…
• Medical microbiology is the study of
microbes, that infect humans, the disease they
cause, and their diagnosis, prevention and
treatment.
• As microbes are invisible to the naked eye, an
instrument (microscope) was needed through
which microorganisms could be observed.

5. a. Early years of microbiology
• The credit of first observing and reporting
bacteria goes to Anton van Leeuwenhoek
(1632–1723)
• his hobby was to grind lenses and observe
diverse materials through them.

6. Contd…
• Before Van
Leeuwenhoek’s
discovery of
microorganisms in 1675,
it had been a mystery
why grapes could be
turned into wine, milk
into cheese, or why food
would spoil.

7. Contribution of Anton Van
leeuwenhoek
• Descriptions of Protozoa, basic types of bacteria, yeasts
and algae.
• In 1676, he observed and described microorganisms
such as bacteria and protozoa as “Animalcules”.
• Described different morphological forms of bacteria
• 1st to record observations of muscle fibers, bacteria,
spermatozoa and blood flow in capillaries (small blood
vessels).
• The term microbe is used by Sedillot in 1878.

9. Robert Hooke [1678]:
• Developed Compound
microscope
• 1st to coin the term ‘Cell’

10. Theory of Spontaneous Generation
• Spontaneous generation is the belief that, on
a daily basis, living things arise from nonliving
material, and this idea was firmly established
throughout most of recorded history.

11. Aristotle's Thoughts on Spontaneous
Generation
• Aristotle was one of the first to record his
conclusions on the possible transition
from nonliving to living.
• According to Aristotle, it was readily
observable that aphids arise from the dew
on plants, fleas from putrid matter, and
mice from dirty hay (straw type grass); and
this belief remained unchallenged for
more than two thousand years.

12. Investigation of Microbial Life
• Microscope, pioneered by Robert Hooke
and Antonie van Leeuwenhoek, enabled
scientific investigators to observe tiny living
organisms that were previously unknown.
• Where did these tiny microbes come from?
Did they generate spontaneously from
nonliving material, or did microbes and other
living organisms only arise from other living
organisms?

13. Contd…
• The invention and refinement of
microscopes raised the debate over
spontaneous generation, and open the door
of research uncontrollably (violently), over the
next 200 years, that would finally put an end
to this idea.

14. Contd…
• Francesco Redi demonstrated that maggots
come from flies, not from putrid material.

15. Contd…
• Lazzaro Spallazani revealed that microbes
could be eliminated from broth that was
placed in sealed containers and heated to high
temperatures.

16. History contd…
• Finally, Louis Pasteur
(father of microbiology),
the French chemist and all
around scientific
overachiever, performed
several experiments which
demonstrated conclusively
that life arose only from
living predecessors.

17. Pasteur’s Swan Neck Flask Experiment
• In his famous experiment, Louis Pasteur used a
special flask whose neck was shaped like an S
or the neck of a swan, hence the name “Swan
Neck Flask.”
• He put a nutrient rich broth in the flask, which
he called the “infusion.”
• He then boiled the infusion killing any
microorganisms which were already present.
Then he allowed the infusion (broth) to sit.

18. Pasteur’s Swan Neck Flask Experiment
Contd…
• Because of the shape of the flask, the infusion
was exposed to air. However, dust particles
and other things in the air never made it into
the infusion.
• Because they were trapped in the curve of the
Swan Neck Flask. No matter how long he
allowed the flask to sit, microorganisms never
appeared in the infusion.

20. Pasteur’s Swan Neck Flask Experiment
contd…
• However, if he tipped the flask and allowed the
things trapped in the neck to get into the
infusion then microorgranisms began to appear
in the infusion and multiply rapidly.
• This demonstrates that microorganisms do not
appear as a result of Spontaneous Generation.
• Instead, they are introduced into food through
dust particles and other things that happen to
land on the food.

21. What Is Abiogenesis?
• Spontaneous generation was not a theory that
addressed the origin of life, but instead, had been
based on the belief that living things commonly
emerge from nonliving matter.
• Although science ultimately established that
living things arise from other living things, the
question remained…”Where did the first living
thing come from?”
• Abiogenesis is the theory that addresses the
actual origins of life on Earth.

22. Abiogenesis and Nucleic Acids
• All living things have genetic instructions
made of organic molecules called nucleic
acids.
• These nucleic acids are essentially the
blueprint for each living thing.
• Therefore the question of how life on Earth
originated, the investigation of abiogenesis,
focuses on how the first nucleic acids came
into being.

23. Oparin's Origin of Life
• Fossil evidence and molecular biomarkers,
such as carbon isotopes, show that microbes
existed on earth 3.5 billion years ago.
• These cellular microbes were complete living
cells, so the origin of genetic chemicals had to
precede these live forms.

24. Contd…
• But there was no solid theory on abiogenesis until
1924, when Aleksandr Ivanovich Oparin, a
Russian biochemist, presented his ideas in his
publication The Origin of Life.
• Oparin proposed a theory that life on Earth
developed through gradual chemical evolution of
carbon-based molecules within a primordial soup.
• Since Oparin’s significant contribution, scientists
continue to investigate the specific sequence of
chemical events that led to organization of the
first nucleic acids.

25. b. Golden age of microbiology
• From the late 1800s to early 1900s is known
to be the golden age of microbiology.
• Invention of microscope make able to observe
minute partcles and this led to the start of the
golden era of Microbiology.
• The two main scientists who contributed a lot
to this field were Louis Pasteur and Robert
Koch.

26. Contribution of louis Pasteur
• He coined the term “microbiology”, aerobic, anaerobic.
• Disproved the theory of spontaneous generation.
• Developed the concept of fermentation.
• He developed live attenuated vaccine for the disease.
• Invention of vaccine for rabies and anthrax
• Invention of pasteurization technique for sterilization of milk,
wine
• Introduction of sterilization techniques: development of steam
sterilizer, autoclave and hot-air oven
• He was the director of the Pasteur Institute, established in 1887
• Pasteur demonstrated diseases of silkworm was due to a
protozoan parasite.

27. Law of attenuation

29. Contd…
• Louis pasteur attenuated anthrax bacillus by
incubation at high temperatures (42ᵒC-43ᵒC) and
proved that inoculation of such bacilli in animals
introduced protection against anthrax
• He coined the term ‘Vaccine’ for such
prophylactic preparations.
• While working on rabies, he could not isolate any
microorganism from dog and man but suggested
that causative agent of rabies was too small to be
seen by microscope.

30. John Tyndall (1820 - 1893)
• He discovered highly resistant bacterial
structure, later known as endospore.
• Prolonged boiling or intermittent heating was
necessary to kill these spores, to make the
infusion completely sterilized, a process
known as Tyndallisation.

31. Lord Joseph Lister (1827-1912)
• He is the father of antiseptic surgery.
• Lister concluded that wound infections too
were due to microorganisms.
• He also devised a method to destroy
microorganisms in the operation theatre by
spraying a fine mist of carbolic acid into the
air.

32. Contribution of Robert Koch
• Father of morden
bacteriology
• he identified the specific
causative agents
of tuberculosis (koch
bacilli;Mycobacterium
tuberculosis), cholera
(Vibrio cholerae),
and anthrax (Bacillus
anthracis).

33. Contd…
• Gave Koch Postulates (a series of four generalized
principles linking specific microorganisms to specific
diseases that remain today the "gold standard" in
medical microbiology)
• Koch pioneered the use of agar as a base for culture
media.
• He also introduced methods for isolation of bacteria in
pure culture.
• He described hanging drop method for testing motility.
• He introduced staining techniques by using aniline dye.

34. Contd…
• Robert Koch used gelatin to prepare solid media
but it was not an ideal because
(i) Since gelatin is a protein, it is digested by many
bacteria capable of producing a proteolytic
exoenzyme gelatinase that hydrolyses the protein
to amino acids.
(ii) It melts when the temperature rises above 25°C.
• Agar is better than gelatin because of its higher
melting pointing (96°c) and solidifying (40 –
45°c)points.

35. “To teach is to learn”

37. Limitations of Koch postulates
• Viruses were not yet able to be cultured .
• The third postulate says that the experimental host
“should” exhibit disease, not “must”. This is because
asymptomatic carriers, immunity, and genetic resistance
are possible.
• Koch’s Postulates do not account for prion diseases and
other agents that cannot be grown in culture.
• Most of the human bacterial pathogens satisfy Koch’s
postulates except for those of Mycobacterium
leprae and Treponema pallidum, the causative agent of
leprosy and syphilis, respectively. Both these bacteria
are yet to be grown in cell-free culture media.

38. c. Modern age of microbiology
• Modern microbiology began with the
discovery of microbes, and the scope and
scale of the field continues to expand today.
• The modern microbiology in relation to the
molecular biology focus on the detection of
microbes on the basis of genetics.
• In such tests the genetic material of the
microbes are analyzed.
• It may includes PCR, DNA hybridization, DNA
probe tests, recombinant DNA technology etc.

39. • Richard Petri (1887)
• He developed the Petri dish (plate), a
container used for solid culture media.
• Edward Jenner (1749-1823)
• First to prevent small pox.
• He discovered the technique of vaccination.
• Alexander Flemming
• He discovered the penicillin from penicillium
notatum that destroy several pathogenic
bacteria.

41. IMPORTANT DISCOVERIES:
• Bacteria:
• Hansen (1874) – Leprosy bacllus
• Neisser (1879) – Gonococcus
• Ogston (1881) – Staphylococcus
• Loeffler (1884) – Diphtheria bacillus
• Roux and Yersin – Diphtheria toxin

42. Contd…
• Viruses:
• Beijerinck (1898) - Coined the term Virus for
filterable
• infectious agents.
• Pasteur developed Rabies vaccine.
• GoodPasteur - Cultivation of viruses on chick
embryos.
• Charles Chamberland, one of Pasteur’s associates
• constructed a porcelain bacterial filter.
• Twort and d’Herelle - Bacteriophages.
• Edward Jenner - Vaccination for Smallpox

43. MODERN ERA:
• Nobel Laureates
• Years Nobel laureates Contribution
• 1901 Von behring Diptheria antitoxin
• 1902 Ronald Ross Malaria
• 1905 Robert koch Tb
• 1908 Metchnikoff Phagocytosis
• 1945 Flemming Penicillin
• 1962 Watson,Crick Structur DNA
• 1968 Holley,Khorana Genetic code
• 1997 Pruisner Prions
• 2002 Brenner, Hervitz Genetic regulation of organ
development &cell death