culturing microorganisms

• independent variable - types of antibiotic
• dependent variable - area of the inhibition zone of each anitobiotics
• control variables - same growing time
• 1. wash handdis
  2. infect the working area
  3. work near a Bunsen burner - prevent contamination
  4. sterilise agar plate in an autoclave
• agar is used to make plates because it solidifies at room temperature, allows bacteria to grow on its surface, prevents bacterial growth from spreading into liquid medium.
• sterile technique is important when making agar plates as any contaminants will cause unwanted growth.
• step 1 - sterilise the inoculating loop at the Bunsen Burner (hottest place)
• step 2 - take the liquid culture mouth and flame the mouth - prevent bacteria
• step 3 - dip into the bacteria culture
• step 4 - flame the mouth of the bottle again
• step 5 - transfer to the agar plate - scrape in zigzag motion (use the lid as a shield while doing that)
• step 6 - place antibiotic paper disc
• step 7 - lid needs to get secure by tape - bacteria can't get in or out, growing aerobic bacteria instead of anaerobic bacteria
• step 8 - put the agar plate upside down - prevent condensation
• step 9 - put it in an incubator (around 2 days, 25 degree within school)
• Bacteria population increase exponentially by binary fission.
• The population stop increase and decrease due to lack of food and space.
• Inhibition zone is calculated by the area of the circle
• binary fission is to replicate nucleoid and plasmids (DNA), split into two and form two identical daughter cells
• bacteria division = x * 2^n
• x = initial population
• n = how many times it divided
• inhibition zone = radius^2 * pi
• the larger the inhibition zone, the more effective the antibiotic is