January 17, 2022
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
You finish on this topic!