Introduction to Microbiology
Topics Covered
 Scope of Microbiology
 Importance of Microorganisms
 Characteristics of Microorganisms
 History of Microbiology
Microbiology
The word “Microbiology ”comes from the Greek word
“Mikros” , “Bios” and “Logos” .
Here,
* “Mikros” means small
* “ Bios” means life,
* “Logos” means discourse.
So,Microbiology is the study of living organisms of
microscopic size.
Microorganisms:
 Microorganisms are beings things too small to be seen
clearly by unaided eye .
 Examples:
1. Bacteria,
2.Viruses,
3.Fungi,
4.Algae and
5.Protozoa.
Branches of Study
 Bacteriology
study of bacteria
 Mycology
study of fungi and yeast
 Virology
study of viruses
 Parasitology study of parasitic protozoans and
helminths
 Immunology
study of the humoral and cellular
immune response to disease
agents and allergens
Specializations in Microbiology
 Epidemiology and Public Health Microbiology
distribution and spread of diseases and their control and prevention
 Food Microbiology
use of microbes in the production of food products and drinks
 Agricultural and Veterinary Microbiology
use of microbes to increase crop and livestock yield and control of plant
pests and animal diseases
 Environmental Microbiology
study of the beneficial and harmful effects of microbes on the
environment
Importance of Microbiology
 First bacteria
 Photosynthesis and decomposition
 Human use of microorganisms
The Progenote
Evolutionary Timeline: Bacteria appeared 3.5 billion years ago
Photosynthetic Microbes
Microbes are involved in photosynthesis and accounts for
>50% of earth’s oxygen.
Also involved in decomposition and nutrient recycling.
Beneficial Uses of Microbes
Extraction of copper from ore
Beneficial Uses of Microbes
Synthesis of drugs, hormones and enzymes
Beneficial Uses of Microbes
Bioremediation is the use of microbes to degrade organic
matter in sewage and detoxify pollutants such as oil spills.
Modern Uses of Microbes
 Biotechnology, the use of microbes as miniature
biochemical factories to produce food and chemicals is
centuries old.
 Genetic engineering makes use of molecular biology and
recombinant DNA techniques as new tools for
biotechnology.
 Gene therapy replaces missing or defective genes in
human cells through genetic engineering.
 Genetically modified bacteria are used to protect crops
from pests and freezing.
Size of Microbes
Microbes vary in size ranging
from 10 nm (nanometers) to 100
mu (micrometers) to the
macroscopic.
Viruses in nm = 10-9 m (meter)
Bacteria in um = 10-6 m
Helminths in mm = 10-3 m
Prokaryotic
cells
 Nucleus and other membrane-bound
organelles – Absent
 Cell size- Smaller than eukaryotic cells,
usually between 1 to 10 µm
 Reproduction- Asexual, usually by
binary fission
 DNA Content- low. Plasmid DNA is
Common.
 Ribosome- slower ribosome
sedimentation (70 S) and evenly
dispersed in the cytoplasm
 Example- Bacteria and Archaea
Fig 1. A Prokaryotic cell
(Bacterial cell)
Nucleus and other membrane-bound
organelles- Present
Cell size- Much larger than prokaryotes.
Usually 10-100um
Reproduction- Sexual (Meiosis and mitosis)
Nuclear material- Linear DNA, ‘wound’ around
histone (a type of basic protein)
Diploid genome (more than one copy of each
gene)
Cell wall- Chemically simple; cellulose (in
plants) and chitin (in fungi)
Usually multicellular
DNA content- High. Plasmid DNA is not
common.
Ribosome- Faster ribosomes sedimentation
(80S); Large ribosome in Cytosol or nucleus,
small ribosomes in organelles.
Example- Animal and plant cells.
Fig 2. A Eukaryotic cell
(Plant cell)
Brief History of Microbiology
 The Microscope
 Spontaneous Generation
 Germ Theory
History of Microbiology
 Discovering organisms
First microbes were observed in 1673

Robert Hooke- In 1665 reported that living things were
composed of little boxes or cells


devised the compound microscope and illumination
system
Antoni van Leeuwenhoek- (1632-1723)



He is considered the father of bacteriology
Made simple microscopes and began observing with
them (1674)
Discovered bacteria (he called them animalcules)
History of Microbiology: The
Theories
 Spontaneous Generation
 Many believed in spontaneous generation:
 Aristotle synthesized the hypothesis which stated that
some vital force contained in given organic matter can
create living organisms from inanimate objects.
 In basic terms spontaneous generation stated that
living organisms arise from non living matter.
History of Microbiology: The Theories
Spontaneous Generation

Spontaneous generation was disproved in 1668 by Italian Scientist, Francesco Redi.
Redi’s Experiment:

Redi’s question: Where do maggots come from?

Hypothesized: Redi suspected that flies landing on the meat laid eggs that eventually
grew into maggots

Experiment: Placed meat in three separate jars
History of Microbiology: The Theories
Disproving Spontaneous Generation: Redi’s
Experiment
Jar #1
•
•
•
Left open
Maggots developed
Flies were observed
laying eggs on the
meat in the open jar
Jar #2
•
•
•
Covered with netting
Maggots appeared on
the netting
Flies were observed
laying eggs on the
netting
Jar #3
•
•
Sealed
No maggots
developed
History of Microbiology: The Theories
Spontaneous Generation
 The Question: What causes tiny living things to appear in decaying
broth?
 John Needham- revived the theory of
spontaneous generation in 1745
 Needham theorized that if he took chicken broth and heated
it, all living things in it would die.
 After heating some broth, he let a flask cool and sit at a
constant temperature. The development of a thick turbid
solution of microorganisms in the flask was strong proof to
Needham of the existence of spontaneous generation.
History of Microbiology: The Theories
Spontaneous Generation
The Question: What causes tiny living things to appear in decaying
broth?
 Lazzaro Spallanzani (1729-1799)
 In 1776 he demonstrated that microorganisms were
already in the solution, the container, or the air
 He took solutions which he knew would "breed"
organisms and boiled them for up to an hour. The
flasks were hermetically sealed to keep out
contaminated air.
History of Microbiology: The Theories
Biogenesis
 In 1858 German scientist, Rudolf Virchow
challenged spontaneous generation with his
concept of biogenesis
 Living organisms arise from pre-existing life
 Virchow presented his idea to the scientific
community, but could not back it up with a
convincing experiment
Settlement of Spontaneous Generation
 In 1861, a French scientist by the name of Louis
Pasteur demonstrated where microorganisms
came from

Father of Medical Microbiology

Demonstrated the microorganisms exist in the air and could
contaminate sterile solutions by passing air through cotton filters

The filter trapped tiny particles floating in the air
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Louis Pasteur’s Swan neck
flask experiment
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French
chemist
Louis
Pasteur’s
design of
this experiment settled
the argument.
Louis Pasteur’s experiments
 Louis Pasteur performed numerous experiments to
discover why wine and dairy products became sour
 He found that bacteria were to blame (lactic acid
fermentation)
 Pasteur called attention to the importance of
microorganisms in everyday life and stirred scientists
to think that if bacteria could make the wine “sick,”
then perhaps they could cause human illness.
 In 1864, Louis Pasteur established Pasteursation.
Germ Theory of Disease
 1876 - Robert Koch
provided proof that a
bacterium causes anthrax
using experimental steps
now called the Koch’s
Postulates
 He was the first to use agar
as solid culture medium in
bacteriology.
Koch’s Postulates
 The microbe must always be present in every case
of the disease
 It must be isolated in pure culture on artificial
media
 When inoculated into healthy animal host it
should produce the same disease
 It must be isolated from the diseased animal again
Whittaker’s Five Kingdom Concept
 In 1969 R.H Whittaker proposed five kingdom
concept.
 Monera.
 Protista.
 Plantae.
 Fungi.
 Animalia.
The Scope And Application of
Microbiology In Human Welfare
 Produce Antibiotics.
 Produce Food.
 Agricultural Activities.
 Bioremediation.
 Sewage Treatment.
 Decompose Organic Matter
 Recycling Vital Elements
 Insect Pest Control
Application of Microbiology in
Medical Sector
 Produce Antibiotics
 Produce Vaccines.
 Use microbes in Diagnostic procedures.
 Preventive measures.
 Prevent the causative agents.
Application of Microbiology in
Agriculture
 Nitrogen Fixation.
 Sulfur Oxidizing.
 GM Food.
Sanitation and Environmental
Pollution Control
Sanitation and Environmental
pollution control
 Huge number of microorganisms are used to
sanitation and environmental pollution control.
1. Prevent the sewage pollution and degradation of
toxin.
2. Prevent the pollution of ponds ,rivers and oceans
water.
3. Prevent the pollution of air ,water ,soil and on plants
and animals.
4. Control of infections diseases of pathogens.
Application of Microbiology
Dairy Industry
i. Milk
ii. Yogurt
iii. Cheese
iv. Buttermilk
i. Milk
Most milk is treated by pasteurisation.
Method:
1. Heat milk to 72ºC for 15 seconds.
2. Cool quickly to below 10ºC.
3. Pack in bottle, carton or container.
Pasteurised milk will keep for up to
five days in a fridge.
ii. Yogurt
1.
Heat milk to 43oC (helps bacteria grow)
2.
Add 1 teaspoon of starter culture.
3.
Cover with cling film.
4.
Incubate yoghurt at 43oC for 7 hours.
5.
When ready, place yoghurt in fridge for 4
hours.
Food industry
i. Bread
ii. Beer
iii. Salami