Download ex: Gram stain

Kingdom: Monera
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Division: Eubacteriophyta
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Class: Bacteria
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They are prokaryotic organisms:
(they Don’t have organized nucleus
surrounded by nuclear membrane and
the DNA found free in the cytoplasm).
organisms made up of just one cell.
capable
of
multiplying
by
themselves, as they have the power
to divide , this is called ( binary
fission).
some bacteria can cause diseases.
BACILLUS
SPIRILLUM
COCCUS
vibrio
Aggregation of coccus shape:
monococcus
Staphylococci
Aggregation of Bacillus shape
monobacillus
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Is a mixture of various nutrients which
are suitable for the growth of
microorganisms
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At least 500 different types
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Solid or liquid
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Inoculated by loops, needles, pipettes,
and swabs
Types of media
Based on the physical state
 Liquid medium:
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Solid medium:
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Without agar.
for the proliferation of bacteria.
1.5-2.5% agar.
for the isolation and identification of bacteria
e.g., slant, Petri dishes.
Semisolid medium:
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0.3-0.5% agar.
for the observation of bacterial motility and
preservation of bacteria.
Semisolid
media
Liquid
media
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1.
2.
3.
4.
5.
6.
We can isolate bacteria from any source:
Air
Water
Dust
Human body ex.“skin, mouth and nails”
Foods
Any other sources
Bacterial growth on culture media
 Shape of
colony
 Edge
 Elevation
Staining of Bacteria
Bacterial cells are almost colorless and
transparent
A staining technique is often applied to
the cells to color them →
Their shape and size can be easily
determined under the microscope.
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Staining may be a simple stain ( use
only one type of stain ex: methylene
blue) or complex stain ( ex: Gram stain)
Smear Preparation:
Preparation and Fixation of Bacteria for
Staining.
Objective:
To kill the microorganism & fix them to
the slide to prevent them from being
washed out during the process of
staining.
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Flame the loop and let it to cool.
Put the bacterial suspension on a
clean slide.
Fix the bacterial suspension by flam
(avoid overheating).
Gram Stain:
It is the most important
differential stain used in
bacteriology because:
it classified bacteria into
two major groups:
a)Gram positive:
Appears violet after
Gram’s stain
b) Gram negative:
Appears red after Gram’s
stain
Procedure:
Crystal violet
(30-60 sec)
↓wash with water
Iodine
(2 min)
↓ wash with water
Alcohol
(10 sec)
↓ wash with water
Safranin
(1 min)
wash with water, dry and examine with
oil lens
Shape: Cocci
Aggregation: irregular clusters
Colour: Violet
Gram’s reaction: Gram’s +ve
Gram positive Staphylococci
Shape: Bacilli
Aggregation: Single
Colour: red
Gram’s reaction: Gram’s –ve
Gram negative monobacilli