1. Classification of bacteria
Kingdom: Monera
Division: Eubacteriophyta
Class: Bacteria

2. What is bacteria?
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.

3. Common Shapes of Bacteria
BACILLUS
COCCUS
vibrio
SPIRILLUM

4. Aggregation of coccus shape:
monococcus
Staphylococci

5. Aggregation of Bacillus shape
monobacillus

6. Culture medium
Is a mixture of various nutrients which are suitable for the growth of microorganisms
At least 500 different types
Solid or liquid
Inoculated by loops, needles, pipettes, and swabs

7. Types of media Semisolid medium: Based on the physical state
Liquid medium:
Without agar.
for the proliferation of bacteria.
Solid medium:
% agar.
for the isolation and identification of bacteria
e.g., slant, Petri dishes.
Semisolid medium:
% agar.
for the observation of bacterial motility and preservation of bacteria.

8. Semisolid media
Liquid media

9. Where we can find and isolate Bacteria?
We can isolate bacteria from any source:
Air
Water
Dust
Human body ex.“skin, mouth and nails”
Foods
Any other sources

10. Bacterial growth on culture media

11. Bacterial growth in culture medium

12. Colony morphology
Shape of colony
Edge
Elevation

13. 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.
Staining may be a simple stain ( use only one type of stain ex: methylene blue) or complex stain ( ex: Gram stain)

14. Preparation and Fixation of Bacteria for Staining.
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.

15. Smear preparation Flame the loop and let it to cool.
Put the bacterial suspension on a clean slide.
Fix the bacterial suspension by flam (avoid overheating).

16. Appears violet after Gram’s stain
Gram Stain:
It is the most important differential stain used in bacteriology because:
it classified bacteria into two major groups:
Gram positive:
Appears violet after Gram’s stain
b) Gram negative:
Appears red after Gram’s stain

17. wash with water, dry and examine with oil lens
Procedure:
Crystal violet
(30-60 sec)
↓wash with water
Iodine
(2 min)
↓ wash with water
Alcohol
(10 sec)
Safranin
(1 min)
wash with water, dry and examine with oil lens

18. Gram Staining Procedure

19. Results: Gram positive Staphylococci Shape: Cocci
Aggregation: irregular clusters
Colour: Violet
Gram’s reaction: Gram’s +ve
Gram positive Staphylococci

20. Results: Gram negative monobacilli Shape: Bacilli Aggregation: Single
Colour: red
Gram’s reaction: Gram’s –ve
Gram negative monobacilli

21. Thank You