Culturing microorganisms

• Bacteria multiply by simple cell division (binary fission) as often as once every 20 minutes if they have enough nutrients and a suitable temperature
• Bacteria can be grown in a nutrient broth solution or as colonies on an agar gel plate
• Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants and antibiotics
• How to prepare an uncontaminated culture using aseptic technique

  1. Sterilise petri dish
  2. Pass inoculating loop through flame
  3. using inoculating loop to transfer bacteria on the petri dish
  4. Attach petri dish lid using adhesive tape
  5. place agar plate upside down into incubator
• • Petri dish must be sterilised before use to kill any unwanted microorganisms
  • inoculating loop is passed through a flame to sterilise the loop
  • Petri dish lid is attached using an adhesive tape to stop microorganisms in the air getting in
  • Agar plate is placed upside down to stop condensation
  • we incubate bacteria at 25 degrees in school to reduce chance of harmful bacteria growing
• Binary fission

  number of bacteria= 2 to the power of number of rounds of division