Microbiology Lab - Gram Staining & Bacterial Characteristics PDF

## Gram Staining ### Procedure 1. **Crystal violet** 2. **Iodine** 3. **Alcohol** 4. **Safranin or Fuchsine** ### Gram-Positive Bacteria * **S. aureus** * **Color:** Violet * **Shape:** Cocci * **Examples:** *Micrococcus luteus* ### Gram-Negative Bacteria * **Color:** Pink *...

## Gram Staining ### Procedure 1. **Crystal violet** 2. **Iodine** 3. **Alcohol** 4. **Safranin or Fuchsine** ### Gram-Positive Bacteria * **S. aureus** * **Color:** Violet * **Shape:** Cocci * **Examples:** *Micrococcus luteus* ### Gram-Negative Bacteria * **Color:** Pink * **Shape:** Various - Cocci, bacilli, spirals. * **Examples:** *E. coli* ### Schaeffer-Fulton Staining * **Color:** Green * **Purpose:** To stain endospores * **Examples:** * *Bacillus* * *Clostridium* ### Cell Wall Composition of Gram-Positive Bacteria * **Thick peptidoglycan layer:** * Approximately 30% of dry weight * Composed of teichoic acids and lipoteichoic acids * More susceptible to antibiotics ### Cell Wall Composition of Gram-Negative Bacteria * **Thin peptidoglycan layer:** * Approximately 10% of dry weight * Lipopolysaccharide (LPS) layer * Outer membrane ### Culturing of Bacteria | Growth medium | Growth characteristics | Example |---|---|---| | **Liquid (TSB)** | *Growth in suspension* * *Pellet formation at the bottom:* * *Saccharomyces cerevisiae* * *Turbidity* * *E. coli* * *Surface film:* * *Bacillus subtilis* | **Solid (Sabouraud)** | *Colonies:* * *Flat: spreading, smooth* * *Raised: round, dome-shaped* * *Convex* * *Filamentous* * *Irregular* * *Rough* * *Moist:* * *E. coli* * *Dry:* * *Bacillus subtilis* | **Kligler's Iron Agar** | *H2S production:* * *Black precipitate* * *Urease production:* * *Alkaline slant, acid butt (red slant, yellow butt)* * *Gas production:* * *Gas bubbles* * *CO2 Production:* * *Yellow butt* | ### Bacterial Characteristics | Characteristic | Example |---|---| | *Slime production* | *Pseudomonas* | *Pigment production* | *Staphylococcus aureus* | *Colony morphology: spreading colonies* | *Proteus* | *Rapid multiplication* | *E. coli*