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Microbiology is the science that deals
with the study of too small organism
(micro-organisms) that are invisible to the
naked eye
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Laboratory Rules
and Safety
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Instructions and Rules
☠ No eating or drinking.
☠ Lab coat & marker.
☠ Aseptic technique.
☠ Benches must be
disinfected.
☠ Discarded cultures &
infectious materials.
☠ Avoid contamination.
☠ Broken or spilled
living cultures.
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☠ Microscope.
☠ At the end of each lab
check:
Gas tap is turned off.
Water tap is closed
properly.
Microscope lamp is
turned off.
☠ Finally wash your
hands thoroughly.
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Introduction to Microbiological
Equipments and Materials
Medium:❊ An artificial preparation contains the
essential elements and nutrients needed
by the m.o to grow (media)
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Culture media
It may be:
 Liquid (broth)
 Solid (containing agar)
 Semisolid (containing low conc. of agar)
❊
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Introduction to Microbiological
Equipments and Materials
Inoculation: Culturing of sterile media with
m.o [Inoculation loop].
Incubation: Placing the culture into the
incubator at optimum temperature for
growth.
Sterile: Free from any living
microorganism
Contamination: Introduction of undesirable
m.o.
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Identification of Bacteria
Microscopical Examination:
• Examination of wet mount preparation.
• Examination of stained preparation.
Macroscopical Examination:
• Characters of colonies.
• Hemolysis on blood agar.
• Pigment production.
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Identification of Bacteria
Biochemical Tests.
Additional Tests:
• such as seriological tests
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Colony vs. Cell
Colonies
Cells
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Colony vs. Cell
Colonies
Cells
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The Microscope
The microscope is the most important tool used
for examination and identification of
microorganisms.
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History
Robert Hooke: Lived
from 1635 – 1703.
– Invented a microscope he
used to observe slices of
cork.
– Used the term “cell” to
describe the box structure
of the cork plant.
– “Father of Microscopy”
The Microscope
Uses of microscope:
1. Identification of microbial groups.
(Bacterial, Fungi, Protozoa)
2. Morphological studies of m.o
(size, shape, arrangement…..)
3. Physiological studies
(motility and reproduction….)
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The Microscope
Types of microscopes:
1. Optical microscope:


Use light beams and lenses
The most common one used in the lab
2. Electronic microscope:


Use electron beams and magnetic fields
Used for examination of viruses and sections
of bacteria
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Optical microscope vs.
Electronic microscope
Optical microscope
Electronic microscope
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Optical microscope vs.
Electronic microscope
Optical microscope
Electronic microscope
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Optical microscope vs.
Electronic microscope
Optical microscope
Electronic microscope
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Electronic microscope
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The Microscope
Optical microscope:
 There are two types
a- Simple microscope: single system
of lenses
b- Compound microscope: has two
lens system, the ocular lens and the
objective lens
 The two lenses system give greater
magnification
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Components of the compound
microscope
Ocular lens
Objective lens
Stage
Iris diaphram
Lamp box
Slide movement knob
Fine adjustment
Coarse
adjustment
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The Eyepiece is Commonly
Described as the Ocular
lens.
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Theoretical principles of
microscopy
Magnification:
It means enlargement of the linear
diameter of an object.
It is the function of two lens system
[the ocular and the objective lens]
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Theoretical principles of
microscopy
Total magnification =
mag. power of ocular lens X mag. power of
objective lens used
1.
2.
3.
4.
Objective lens
mag. Power
Scanning lens
4×
Low power objective lens
10×
High power objective lens
40×
Oil immersion lens
100×
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Theoretical principles of
microscopy
The magnification power of ocular lens
(eye piece) is 10×
The total magnification will be 40, 100,
400, 1000 times.
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Theoretical principles of
microscopy
Working distance:
It is the distance between the objective
lens and the slide.
General rule, as the magnification of
the lens increase the working
distance decrease.
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Theoretical principles of
microscopy
Resolution:
It is the ability of a lens to reveal two
closely adjacent points as separate and
distance.
The resolving power of the oil immersion
lens depends on the addition of special oil
(Ceder wood oil) between the specimen
slide and the objective lens.
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Which image is least resolved?
Resolution:
Higher Resolution;
note the “Sharpness”
of the Image.
Lower Resolution; it
is less sharp.
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Oil Immersion Increases Resolution
Air has a different Index of
Refraction from water (so light
bends).
Air has a different Index of
Refraction from glass (so
light bends).
The Mineral Oil has the
same Index of
Refraction as glass (so
light does not bend).
Objective
lens
Saved light
Lost light
oil
specimen
Light source
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Examination of wet mount
preparation.
Examination of living bacteria for motility
(Hanging drop technique)
In stained slide preparation the cells are
heat-killed prior to staining. Thus the
motility in not observable .
Direct observation of a drop from a liquid
containing bacteria is an excellent method
of studying motility as in hanging drop
preparations
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(Hanging drop technique)
True motility:- it is the active movement
of the organism from place to place.
Brownian movement:- is a vibratory
movement of the cells due to their
bombardment by water molecules in
the suspension
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(Hanging drop technique)
Materials:–Culture of Proteus vulgaris
–Plasticine, slide, cover slip
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