culturing microorganisms

• what would a solution look like if it contains large amounts of bacteria? cloudy
• what does an agar gel plate contain? nutrient broth but turned into a jelly using a chemical called agar
• how to prevent agar gel plates to be contaminated

  sterilise all petri dishes, bacterial nutrient broth and agar

  sterilise inoculating loop by passing it through a bunsen burner

  cleaning surfaces with disinfectant

  washing hands with antiseptic

  bunsen burner on the bench to kill airborne microorganisms
• how would sterilising all petri dishes, nutrient broth and agar prevent contamination? it will kill all bacteria
• steps to carry out culturing microorganism R.P

  1. sterilise equipment- say how to
  2. use the loop to spread the chosen bacteria evenly over the plate
  3. place sterile filter paper discs containing antibiotic onto the plate
  4. incubate plate at 25 degrees
  5. calculate area of zone of inhibition
• why do school laboratories incubate bacteria at 25 degrees?

  reduces the chances that harmful bacteria will grow
• what to expect for the results of the effects of antibiotics on bacterial growth?

  layer of bacteria formed all over the plate around the antibiotic discs theres a region where bacteria hasn't grown = zone of inhibition - can find area of zone inhibition = pie radius^2
• 4 Conditions needed for bacterial growth

  temperature - most bacteria grow fastest in warm environments

  nutrient availability - bacteria need a good supply of nutrients in order to grow rapidly

  moisture - most bacteria grow fastest in moist conditions

  oxygen - different types of bacteria either need the presence or absence of oxygen for growth
• Why is the Petri dish lid only partially lifted?

  To prevent the entry of microorganisms from the air
• What is the term for the procedures used to prevent contamination when culturing microorganisms?


  Aseptic techniques