Microbiology - GCSE Science Required Practical (Triple)

Summary

Dr. Becks guides students through a practical microbiology experiment involving E. coli, a safe strain of bacteria. The lesson emphasizes proper lab protocols to maintain sterile conditions while handling bacterial cultures. Students learn to prepare agar plates, inoculate them with E. coli, and apply different substances—streptomycin, tea tree oil, and antiseptic—to test their antibacterial effects. The experiment concludes by observing bacterial growth inhibition, comparing results, and discussing the real-world implications of these findings. Dr. Becks also highlights training resources for teachers and technicians in practical science education.

Takeaways

• 🧫 This microbiology practical involves working with a safe strain of E. coli to ensure real-world lab experience while maintaining strict sterile conditions.
• 🧪 Students must set up their equipment, thoroughly wash hands, and work within a sterile area created by the Bunsen burner to avoid contamination.
• 🔬 The agar plate is divided into three sections and labeled with E. coli, the date, and student initials to track the experiment's progress.
• 🧴 Proper sterilization of all tools, including pipettes and spreaders, is critical to maintain a sterile environment and prevent contamination of the bacterial culture.
• 🔥 The Bunsen burner is set to a blue flame to create a sterile working zone, especially important during the inoculation and spreading of the bacterial culture on the agar plate.
• 💊 The experiment includes testing three substances: an antibiotic (streptomycin), tea tree oil, and a commercial antiseptic to observe their effects on bacterial growth.
• 🧫 After inoculation, the bacterial culture is spread evenly across the agar plate to form a 'lawn' of bacteria, allowing the effects of the substances to be observed.
• 🧪 The effectiveness of each substance is determined by the clear rings around the disks, indicating areas where bacterial growth was inhibited.
• 📏 Measuring the diameter of these clear areas provides a way to compare the effectiveness of the antibiotic, tea tree oil, and antiseptic in killing bacteria.
• 📊 The practical highlights considerations about the accuracy of the test, including differences in how substances spread or diffuse, which may affect results.

Q & A

What type of bacterial culture is being used in this microbiology practical?

The bacterial culture being used is a strain of E. coli, which is safe and does not cause sickness.

Why is it important to handle the bacterial culture as though it were dangerous?

Even though the strain of E. coli is safe, all procedures should be followed as though handling a dangerous microbe to prevent contamination and ensure proper lab practices.

What precautions should be taken before handling the agar plates?

Before handling the agar plates, students should wash their hands thoroughly, remove their work mat from the sterilizing solution, and ensure they handle the plates in a sterile area near the Bunsen burner.

Why is it essential to label the bottom of the agar plate instead of the lid?

Labeling the bottom of the agar plate (where the gel is) ensures that the label remains intact even when the lid is removed, preventing any mix-up of samples.

What is the purpose of using the Bunsen burner during the practical?

The Bunsen burner creates a sterile environment by producing a sterile area around the workstation to minimize contamination when handling the bacterial culture.

How is the bacterial culture inoculated onto the agar plate?

The bacterial culture is inoculated using a sterile pipette. After flaming the bottle lid, the culture is drawn into the pipette and then carefully squirted onto the agar plate, which is briefly opened to avoid contamination.

What is the role of the glass spreader in the practical?

The glass spreader, which is sterilized by heat, is used to evenly spread the bacterial culture across the surface of the agar plate, ensuring uniform growth.

What is the purpose of adding antibiotic and antiseptic discs to the agar plate?

The antibiotic and antiseptic discs are added to test their effectiveness in killing or inhibiting bacterial growth. The clear zones around the discs indicate areas where bacteria were killed.

Why is it important not to seal the agar plate completely with tape?

Sealing the agar plate completely would prevent oxygen from entering, which is necessary for the growth of E. coli. However, leaving the plate slightly unsealed ensures oxygen can get in while preventing contamination.

How can the effectiveness of the antibiotic and antiseptic treatments be compared?

The effectiveness of the treatments can be compared by measuring the diameter of the clear zones around each disc. A larger clear zone indicates more effective bacterial inhibition.