lecture for mbbs students. Microbiology is the study of microorganisms usually less than 1mm in diameter which requires some form of magnification to be seen clearly Examples: Viruses Bacteria Fungi Algae Protozoans

1. INTRODUCTION
TO
MEDICAL MICROBIOLOGY

2. What is Microbiology ?
 Micro - too small to be seen with the naked eye
 Bio – life
 ology - study of

3. • Microbiology is the study of microorganisms usually less than
1mm in diameter which requires some form of magnification to
be seen clearly
• Examples:
• Viruses
• Bacteria
• Fungi
• Algae
• Protozoans

4. Cellular Acellular
Prokaryotes Eukaryotes Viruses
Bacteria and
archaea
Fungi,algae,protozoa,
helminths
Viruses and
bacteriophage
s
Types of Microbes
(b) VirusTypes
Bacterial virus
AIDS virus
Envelope
Capsid
Nucleic
acid
(a) Cell Types
Prokaryotic
Chromosome
Ribosomes
Flagellum
Cellwall Cell
membrane
Eukaryotic
Flagellum
Mitochondria
Ribosomes
Cell membrane
Nucleus
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5. Branches of Microbiology
Largest and most complex area of biological
sciences
 Agricultural microbiology
 Biotechnology
 Food, dairy, and aquatic microbiology
 Genetic engineering and recombinant DNA
technology
 Public health microbiology and epidemiology
 Immunology
 Many, many more

6. Sub-Disciplines of Microbiology
• Microbiologists are sometimes referred to by the type
of microbial system that they study
• Bacteriology: Study of prokaryotes
• Mycology: Study of fungi
• Phycology: Study of algae
• Protozoology: Study of protozoa
• Virology: Study of viruses
• Beijerinck, NE: discovered intracellular reproduction of TMV; coined
the term “virus” (1899)
• Immunology: Study of the immune system
• Edward Jenner, UK: developed vaccination (1798)
• Metchnikoff, RU: discovered phagocytes (1884)
• Paul Ehrlich, DE: theory of immunity (1890)

8. Importance of Microbes
• The study of microbiology is relevant to our everyday life in
many different ways.
1.Microbes are the earliest organisms found in the fossil
record (survival, adaptation and evolution)
2.Microbes are ubiquitous (found nearly everyway)
3.They perform essential reactions in the environment
4.Microbes can be harnessed to work for us
5.They sometimes cause infectious diseases

9. Microbes Benefit Humans
1.Bacteria are primary decomposers - recycle nutrients back
into the environment (sewage treatment plants)
2. Microbes produce various food products
• cheese, pickles, sauerkraut, green olives
• yogurt, soy sauce, vinegar, bread
• Beer, Wine, Alcohol

10. 3. Microbes are used to produce Antibiotics
• Penicillin
• Mold
• Penicillium notatum
• 1928 Alexander
Fleming

11. Microbes do benefit us, but they are also capable of causing many
diseases
• Pneumonia Whooping Cough
• Botulism Typhoid Fever Measles
• Cholera Scarlet Fever Mumps
• Syphilis Gonorrhea Herpes 1
• Chlamydia Tuberculosis Herpes 2
• Meningitis Tetanus RMSV
• Strep Throat Lyme Disease AIDS
• Black Plague Diarrhea Gangrene

12. 12

13. HISTORICAL EVOLUTION OF MICROBIOLOGY
“
Scienceisinterdependent andnewdiscoveriesdependupon
earliercontributions frommanyotherscientists
„

15. 15
ANCIENT HISTORY OF MICROBIOLOGY
• 600 BC Romans had built aqueducts and had a “Water
Commissioner”
• Contamination of water supplies (presumably by
microbes) was punishable by death in Rome.
• Fermentation was used by ancient Egyptians to brew
beer
• Isolation of people with leprosy to prevent spread (Leper
colonies)

16.  The belief in the spontaneous
generation of life from
nonliving matter was introduced
by Aristotle, who lived around
350 BC.
 According to Aristotle, it was:
“readily observable that aphids arise from the
dew which falls on plants, fleas from putrid
matter, mice from dirty hay.”
 This belief remained
unchallenged for more than
2000 years.
 Until…
Aristotle: 384 – 322 B.C.

17. Robert Hooke
• 1664
• English naturalist
and architect
• May have been the first
to see microorganisms
• Coined the word “cell”
to describe what he saw
while viewing tree bark
from a cork oak.

18. Antony van Leeuwenhoek
- 1st person to actually see living microorganisms

19. Antony van Leeuwenhoek (1632-1723)
• 1684
• Dutch fabric merchant
• First person to accurately
describe living microbes
• Used a simple microscope
(magnifying glass)
• Made and reported many
detailed observations
“wee animalcules”

22. Reproduction of Leeuwenhoek's microscope
Figure 1.2

23. The Discovery of Microbes
• People have long been
aware of the effects of
microbial growth
• Spoilage, disease,
decomposition
• Microbes are too small to be
seen even with hand lenses
• Microscopes changed that.

24. Pasteur designed special “swan-necked
flasks” with a boiled meat infusion

25. Robert Koch
Figure 1.15

26. • Koch’s Contributions
• Simple staining techniques
• First photomicrograph of bacteria
• First photomicrograph of bacteria in diseased tissue
• Techniques for estimating CFU/ml
• Use of steam to sterilize media
• Use of Petri dishes
• Techniques to transfer bacteria
• Bacteria as distinct species

27. The Pure Cultures and Isolation of Single Colonies
Koch :
Observation: Slices of potato when
exposed to air, will generate large
number of bacteria (colonies) of
different sizes, colours and forms
Colonies

28. Bacterial colonies on agar
Figure 1.16

29. Problem: Not all bacteria could grow on potatoes!
Solution :
Koch used gelatin as a
means for solidification of rich
culture media.
He formulated various culture
media

30. Disadvantages of Gelatin
• Gelatin liquefaction: It is digested by various
microorganisms eg. gelatinase positive enterococci and
streptomyces
• Low melting temperature: It is in the liquid state above
the temperature of 28oC.

31. Agar
• Polysaccharide derived from
the cell walls of a red algae
(Rhodophyta)
• A polysaccharide polymer that
contains 3,6-anhydrogalactose, 2-
O-methyl-α-l-galactopyranose and
6-O-methyl agarobiose
• Solid at >37oC.
• Melts at 100oC.
• Not digested by most bacteria
Gracilaria (red seaweeds)

32. Kochs postulates

33. Koch’s postulates

34. • Koch’s Postulates
• Suspected causative agent must be found in every
case of the disease and be absent from healthy hosts
• Agent must be isolated and grown outside the host
• When agent is introduced into a healthy, susceptible
host, the host must get the disease
• Same agent must be found in the diseased
experimental host

35. Development of Vaccines and Antisera
• Edward Jenner in 1796 discovered that cowpox
(vaccinia) induced protection against human
smallpox
• Called procedure vaccination

37. Thank you