Growing and Investigating Bacteria Biology GCSE AQA
- Created by: Caitlinyx
- Created on: 24-04-13 17:54
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- Growing and Investigating Bacteria
- Growing Micro-organisms in the lab
- To culture micro-organisms you need to provide them with everything they need, so they are put in a liquid/gel which contains nutrients - a culture medium
- This contains carbohydrates for an energy source along with other minerals and sometimes chemicals
- You can provide the nutrients in agar jelly. Hot agar jelly is poured into a petri dish and left to cool before adding micro-organisms
- You have to be careful when growing micro-organisms. You may want to grow harmless bacteria, but it can mutate into something more dangerous
- You want to keep the strains of bacteria away from other pathogens
- Contamination may come from your skin, the air, the soil or the water
- Investigation needs uncontaminated cultures of micro-organisms
- To culture micro-organisms you need to provide them with everything they need, so they are put in a liquid/gel which contains nutrients - a culture medium
- Growing Useful Organisms
- Petri dishes on which you culture the micro organisms, and the agar jelly, needs to be sterilised before use, to kill all unwanted pathogens
- Oven called autoclave sterilises by using high pressure steam
- Petri dishes often bought ready sterilized
- UV or Gamma radiation used to kill bacteria
- Next step is to innoculate the sterile agar with the micro-organisms you want to grow
- Sterilise innoculating loop by heating it until it is red hot in the bunsen burner and then beave it to cool
- Dip the sterised loop in the bacteria and use it to make zig-zag streakes on the surface of the agar. Replace the lid quickly to avoid contamination
- Seal the lid of the Petri dish with tape to prevent micro-organisms in the air from contaminating the petri dish, or micro-organisms from escaping. Do not seal all the way so oxygen can get in and anaerobic bacteria does not grow
- They need to be incubated for a few days so the micro-organisms can grow
- Schools and colleges do not keep them over 25.C because it reduces the chance of harmful bacteria growing
- In industrial conditions bacterial cultures are kept at higher temperatures so they can grow at higher rates
- Petri dishes on which you culture the micro organisms, and the agar jelly, needs to be sterilised before use, to kill all unwanted pathogens
- Growing Micro-organisms in the lab
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