Practical 6

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  • Practical 6
    • Aseptic techniques
      • Washing hands and disinfecting/sterilising surfaces to kill any pathogens
      • Flame the sterilising inoculating loop
      • Flaming the neck of the culture tube
      • Lifting the petri dish a small amount to prevent contamination
      • Streaking the plate quickly with the inoculating loop
      • Aseptic techniques are needed to avoid contamination which could affect results and potentially harm someone
        • Water can be used as a control as it will not kill any bacteria, showing any bacteria that is killed is due to the antibiotic
    • Inhabitation zones
      • = where bacteria cannot grow due to the antibiotic
      • The larger the zone, the more bacteria killed
      • If there is no zone, that means the bacteria is resistant to the antibiotic, as it was able to grow
        • Bacteria can become resistant to an antibiotic due to a random mutation, resulting in a new allele being formed
          • The resistant bacteria survive, and the non-resistant bacteria are killed off, resulting in a strain of bacteria resistant to a certain antibiotic
    • The antibiotic diffuses through the agar, so needs time to do so. As it diffuses through, it kills any bacteria
    • Bacteria is spread onto the agar via the inoculating loop, which is then spread. Soak a paper disc in different antibiotics and place onto the agar plate. Tape the lid on and lightly incubate at 25 degrees for 48 hours. All aseptic techniques should be used


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