Culturing Microorganisms

• What substance can bacteria be grown in?

  Culture medium
• What can a culture medium be?

  • Nutrient broth solution
  • Agar jelly
• How does bacteria grow on an agar plate?

  It forms visible colonies on the surface of the jelly
• What tool is used to transfer bacteria to the culture medium?

  An inoculating loop
• What temperature must cultures be kept at in school?

  25 degrees celsius
• Why is there a temperature limit for cultures in school?

  In order to prevent the growth of harmful pathogens at higher temperatures
• How do you test antibiotics on an agar plate?

  • Place paper discs soaked in different antibiotics on an agar plate covered in bacteria
  • Non-resistant bacteria will die leaving a clear area
  • Use a control that has been soaked in water in order to ensure that any effect is from the antibiotic itself
  • Leave the plate for 48 hours at 25 degrees elsius
  • The greater the clear area, the greater the effectiveness of the antibiotic
• What is the clear area caused by antibiotics on an agar plate called?

  An inhibition zone
• How do you avoid contamination in a petri dish?

  • Sterilise the petri dishes and culture mediums to kill any microorganisms that are unwanted
  • Sterilise the inoculating loop
  • Lightly tape the lid of the petri dish after transferring the bacteria
  • Petri dish should be stored upside down to stop condensation falling on the agar surface
• How can you sterilise a petri dish and culture medium?

  Heating to a high temperature
• How can you sterilise an inoculating loop?

  Pass it through a hot flame