General Microbiology PDF

# General Microbiology ## Examination of Bacterial Cells - By using some equipment, such as: - Isolation loop - Test tube has 9 ml St. Dis. H2O - Glass slides with their covers. - By using some devices: - Flame - Microscope - By using some chemicals or reagents: This is accordi...

# General Microbiology ## Examination of Bacterial Cells - By using some equipment, such as: - Isolation loop - Test tube has 9 ml St. Dis. H2O - Glass slides with their covers. - By using some devices: - Flame - Microscope - By using some chemicals or reagents: This is according to the type of staining method. ## Examination: - **Living cells:** By Hanging drop - **Fixed cells.** - **Fixed Bacterial cells** - Means, the bacterial cells have no ability to move, but they are still alive. It is used to study the size and morphology (shape) of bacterial cells. - **By using chemicals**: It is not preferable due to chemicals making deformation and abnormalities in bacterial cell, shape. - **By use flame**: It is known as preparation of bacterial film (or) bacterial smear. ## Bacterial film (or) Smear: ### Procedures: 1. Prepare bacterial suspension 2. Bring clean glass slide 3. Take a drop of bacterial suspension on (1/3 part) of clean glass slide 4. Dry the suspension or put it on the heat of the flame. Until the suspension dries. ## Gram Stain: - Distinguish between gram positive and gram-negative bacteria (G+ve, G-ve) ### Procedures: 1. Prepare bacterial film/smear 2. Put crystal violet on it, let it for 1 min. 3. Wash the slide by tap water, to remove the excess of crystal violet. 4. Put iodine on the smear, let it to stand for 1 min. 5. Wash with tap water, to remove the excess of stain. 6. Wash with (ethanol 70%), drop by drop to remove the excess stain. 7. Wash again with tap water. 8. Put Safranin and let it to stand for 45 sec. 9. Wash with tap water drop by drop. 10. Dry the slide by using dry filter paper and then examine it by using oil immersion lens. ## Observation: - G+ve bacteria have violet color of crystal violet. - G-ve bacteria have red color of Safranin. ## Notes: - **Primary stain:** Crystal violet. - **Counter stain:** Safranin. - **Mordant:** Iodine. - **Alcohol**: Lipid hydrolysis, dehydrating agent, decolorizing agent. ## Comment: | | G+ve | G-ve | |----------------------|------|------| | Chemical Structure of the cell wall | | | | My ribonucleate | | | | Lipid Content of the cell wall | Small | Large | | Mg-ribonucleate | | | | | CV | CV | | | | CVIZ | | MgRNA CW IZ Complex | | | | MgRNAIZ | Simple | | | | | | | | ethand | Safranine | | | | CUIZ | | | | | | lipid | Safranin | lipid | | | | content | - **Violet of CV** - **Red of Safranin**