RPA 2 - Culturing microorganisms

Preparation for practical

1. First sterilise all petri dishes, bacterial nutrient broth and agar which kills any unwanted microorganisms and prevents contamination

2. Sterilise the inoculating loop by passing it through a flame

3. Next attach the lid of the petri dish using adhesive tape. This stops the lid from falling off and unwanted microorganisms entering

4. Then place the agar plate upside down into an incubator. This stops moisture from dripping down onto the bacteria and disrupting the colonies.

Inoculating loop

How bacteria are transferred into the culture

Temperature to incubate bacteria and why

Normally 25 which reduces the chance that harmful bacteria will grow

Method

1. Clean bench with disinfectant solution

2. Sterilise an inoculating loop

3. Open a sterile agar gel plate near a bunsen burner flame which kills the bacteria

4. Now use the loop to spread the chosen bacteria evenly over the plate

5. Place sterile filter paper discs containing antibiotic onto the plate

6. Incubate at 25 degrees

Zone of inhibition

Region where bacteria has not grown