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I/GCSE Biology: Keeping things sterile

Keeping things sterile

· biology,igcsse biology,sterile,gcse biology

Growing Bacteria

In I/GCSE Biology, growing bacteria is about...

  • Nutrients needs to grow and reproduce B and Fungi
  • Nutrients often supplied to the microorganisms in a gel called agar (agal bati lol)
  • Agar = growth/culture medium
  • Agar melts at 98°C and can be poured into a Petri dish. Solidifies at 44°C
  • Agar cannot be digested by microbes, so the agar is not used up
  • Microbes need nutrients, temperature between 25 and 45 °C
  • Pathogens grow less at low temperatures (school lab – 25°C, set in incubator)

Why do we need to keep things sterile?

  • Sterile = free from bacteria or living microorganisms
  • Large no. of bacterial cells grown when culturing microorganisms in a lab
  • Safety procedures need to be followed so that harmful microbes don’t enter the strain you are growing and reproduce. (greater health risk if a single cell)
  • Uncontaminated cultures are prepared by using sterile or aseptic equipment
  • Pressurised steam used to serialise glassware and culture media in an auto clave – 121°C for 15min
  • Petri dishes sterilised – ultraviolet, ionising radiation
  • Until lid is opened, Petri dishes remain sterilised

Safety first

  • Follow safety procedures (e.g. avoid hand to face contact while culturing)
  • Risk of airborne microbes fallen into culture plates is minimised by upward movement of air around the Bunsen burner

Inoculation

In I/GCSE Biology, inoculation is about...

  • The process of transferring microbes to the culture medium
  • Inoculation loop used for solid agar
  • Step 1 – Pour the plate
  • Step 2 – Sterilise inoculation loop in flame
  • Step 3 – Collect microbes from pure culture
  • Step 4 – Inoculate Petri dish by sweeping loop back and forth across agar surface
  • Step 5 – Seal Petri Dish and write details
  • Before incubation, Petri dishes sealed with adhesive tape
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