Microbiology Lab
Prepared by: Kazhaleh Mohammadi
Knowledge University
2022-2023
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Introduction

Introduction to Microbiology
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Microscopic organisms (microbes) were not seen,
however, until Antony Van Leeuwenhock (1632-1723)
made microscopes with sufficient magnification, then
after, the science of microbiology began.

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• Leeuwenhock observed motile microorganisms taken
from a decayed tooth under the microscope.
• In 1767 and after the convention of compound
microscope, Linnaeus distinguished 6 species of
microbes assigned to one class.
• 600 types of bacteria was figured in 1838.

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Micro + bio + logy
• The biology comes from bios referring to living
organisms and logy means the study of, thus biology is
the study of living organisms.
• Micro means very small, viewed by microscope
• Microbiology is the study of very small living organisms
called microorganisms or microbes, these include
bacteria, algea, protozoa, fungi and viruses.

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• Many bacteria and fungi are Saprophytes.
• Saprophytes break down dead and dying organic materials (plants
and animals) into nitrates, phosphates, carbon dioxide, water and
other chemicals necessary for plant growth.
• Saprophytes also destroy papers, feces and other biodegradable
matters, although they cannot break down most plastics or glass.
• Nitrogen-fixing bacteria, that live in the root nodules of certain plants
called legumes are able to return nitrogen from the air to the soil in
the form of ammonia for use by other plants

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• In 20th century, biological studies of microbes showed that
there are different kinds of microbes, which found in
different ecological niches and have different actions.
• Microbiology then developed into there groups: microbes
responsible for;
• Fermentation: alcoholic fermentation by using grape juice
• Diseases in man, animals and plants
• The cycle of organic matter in the nature

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• Fermentation refers to the microbial decomposition of
vegetable matters which contains mostly
carbohydrates.
• Putrefaction refers to the formation of more unpleasant
products by the decomposition of high protein
materials, such as meat and eggs.

Medical Microbiology
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Medical microbiology concerns the
nature, distribution and activities of
microbes and how they impact on health
and wellbeing, most particularly as
agents of infection.
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• The germ theory of disease:
The contagious diseases are transmitted or
spread by seeds (microbes) either directly or
indirectly (transmitted from diseased to healthy
person).

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• A disease causing microorganisms called pathogens (3% of all
known microbes)
• The others are non pathogenic (97%), the beneficial microbes are
87%
• Microbes live on and in our bodies e.g. skin, in the mouth and
intestine are known as indigenous microflora (or indigenous
microbiota). Some of them cause disease accidentally and known
as opportunistic pathogens (10%)
• Diseases caused by microbes are called infectious disease

Pharmaceutical Microbiology
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Pharmaceutical microbiologists work in
laboratories and offices, where they conduct
research on the effects of microorganisms
on pharmaceutical products. They also work
with other scientists and engineers to
develop new pharmaceutical products and
processes.
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Classification of bacteria in
microbiology
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• Turn the revolving turret so that the lowest power objective lens (eg.
4x) is clicked into position.
• Place the microscope slide on the stage and fasten it with the stage
clips.
• Look at the objective lens and the stage from the side and turn the
focus knob so the stage moves upward. Move it up as far as it will go
without letting the objective touch the coverslip.
• Look through the eyepiece and move the focus knob until the image
comes into focus.
• Adjust the condenser and light intensity for the greatest amount of
light.
• Move the microscope slide around until the sample is in the center of
the field of view (what you see).
• Use the focus knob to place the sample into focus and readjust the
condenser and light intensity for the clearest image (with low power
objectives you might need to reduce the light intensity or shut the
condenser).
• When finished, lower the stage, click the low-power lens into position
and remove the slide.

Diphtheria Bacilli
Typhoid bacillus
Rhodospirillum
Vibrio Cholerae
Staphylococcus Streptococcus pyogenes Streptococcus
Salmonella enteritidis
Bacilli( Rods) Spiral
Coccus