Required Practical: Growing Bacterial Cultures

🧪 Required Practical: Growing Bacterial Cultures

Safety Considerations

• Temperature: Grow cultures at 25°C (not 37°C) to reduce risk of growing harmful pathogens
• Sterilisation: All equipment must be sterilised to prevent contamination
• Personal protection: Wear goggles, gloves, and work near a Bunsen burner flame
• Disposal: Autoclave cultures before disposal
• Sealed plates: Tape petri dishes shut but don't completely seal (allows gas exchange)

Investigating Antibacterial Substances

1. Preparation: Sterilise petri dishes and nutrient agar
2. Inoculation: Spread bacteria evenly across agar surface (bacterial lawn)
3. Treatment: Place paper discs soaked in different antibacterial substances
4. Control: Include disc soaked in water (negative control)
5. Incubation: Leave at 25°C for 24-48 hours
6. Measurement: Measure diameter of clear zones around each disc

Results Interpretation

• Clear zones: Areas where bacteria have been killed or inhibited
• Larger zones: More effective antibacterial substance
• No zone: Substance has no antibacterial effect
• Control importance: Shows that the disc itself doesn't kill bacteria