Practical 1. Differentiation of Bacteria and the Induction of Bacterial Gene Expression During Infection Flashcards
Gram Positive Bacteria
- Rod/Coccus shaped
- Thick peptidoglycan cell wall
- No outer lipid membrane
- No O specific side chains
- Wall teichoic acids
- Lipoteichoic acids
- Capsular protein
Gram Negative bacteria
- Thin peptidoglycan cell wall
- Spherical, rod-shaped or spiral shaped
- Lipopolysaccharide
- Outer lipid membrane
- O specific side chains
- Periplasm
- Outer membrane protein
NO teichoic or lipoteichoic acids
Potassium hydroxide (K-OH) test
- Differentiate bacteria
- The weaker cell envelope/wall of gram negative bacteria will be destroyed by K-OH
- Gram positive stay intact
Purple after gram staining
Gram positive bacteria
Gram negative bacteria
Pink/Red colour
Staphylococcus Aureus
Coccus shaped
Acinetobacter baumannii
Coccoid/Coccobacillus shaped
Escheria coli (E.coli)
Rod shaped
Mycobacterium Tuberculosis
Rod Shaped
Vibrio cholera
Comma Shaped
Oxidase Production
-Differentiate Bacteria
- N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) as
a redox indicator
- Blue: Oxidase-positive
- Colourless: Oxidase-negative
- Pseudomonas as positive control
Oxidative-Fermentative (O/F) Test
- Bacterial growth in the presence (oxidative) or absence of oxygen (fermentative)
- Positive = Yellow
- Negative = Purple
- Paraffin seal
Catalase Production Test
- Differentiate Bacteria
- Catalase: positive or negative
- Catalase converts: Toxic hydrogen peroxide to water and oxygen
- Bacteria onto slide (sterile loop method), add drops of hydrogen bacteria
- BUBBLES of OXYGEN = CATALASE POSITIVE
Hydrogen peroxide + Bacteria = Oxygen BUBBLES
Catalase presence
The “Oxidative fermentative test” tests:
If bacteria can grow in the presence or absence of oxygen
