Infection & ResponseRequired Practical
Required Practical: Growing Bacterial Cultures
Part of Pathogens and Disease Transmission — GCSE Biology
This required practical covers Required Practical: Growing Bacterial Cultures within Pathogens and Disease Transmission for GCSE Biology. Types of pathogens, how diseases spread, transmission methods, and prevention strategies It is section 10 of 19 in this topic. Revise both the method and the reason for each step, because practical questions often test understanding rather than pure recall.
Topic position
Section 10 of 19
Practice
18 questions
Recall
20 flashcards
🧪 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
- Preparation: Sterilise petri dishes and nutrient agar
- Inoculation: Spread bacteria evenly across agar surface (bacterial lawn)
- Treatment: Place paper discs soaked in different antibacterial substances
- Control: Include disc soaked in water (negative control)
- Incubation: Leave at 25°C for 24-48 hours
- 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