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- 1. Serial Dilution: Principle, Method,and Applications A Practical Approach in Microbiology Dr. Sweta Naik Department of Applied Microbiology Fakir Mohan University
- 2. Introduction • • Definitionof serial dilution • • Importance in microbiology (e.g., estimating bacterial concentration)
- 3. Principle of SerialDilution • • Stepwise dilution of a substance in solution • • Constant dilution factor (e.g., 10-fold) • • Reduces dense culture to countable concentration
- 4. Types of SerialDilution • 1. Simple Serial Dilution • 2. Compound Serial Dilution • 3. Double Dilution (two-step)
- 5. Calculating Dilutions • •Final dilution = Volume transferred / Total volume • • C₁V₁ = C₂V₂ • • Example calculations
- 6. Serial Dilution Procedure •1. Label dilution tubes • 2. Add equal volumes of diluent • 3. Transfer a measured volume to next tube • 4. Mix thoroughly • 5. Plate appropriate dilutions
- 7. Diagram of SerialDilution • • Show steps: 10⁰ → 10⁻¹ → 10⁻² → 10⁻³ ... • • Include volume steps (e.g., 1 mL into 9 mL)
- 8. Example: CFU/mL Calculation •• 150 colonies on 10⁻⁴ dilution plate • • CFU/mL = 150 × 10⁴ = 1.5 × 10⁶ CFU/mL
- 9. Applications of SerialDilution • • Microbial count (CFU/mL) • • Antibiotic sensitivity testing • • Phage titration • • Biochemical assays • • Environmental sample testing
- 10. Common Mistakes &Precautions • • Not mixing well between dilutions • • Incorrect pipetting volumes • • Skipping tubes or cross-contamination
- 11. Summary • • Essentialfor quantifying microbes • • Accurate technique ensures reliable results • • Used in clinical, food, and research labs
- 12. Quiz/Activity • • Whatis the dilution factor if you transfer 1 mL into 9 mL? • • How many CFU/mL if 80 colonies on 10⁻³ plate?
- 13. References • • Cappuccino& Sherman: Microbiology: A Laboratory Manual • • Atlas: Handbook of Microbiological Media • • ASM online learning portal