B6 - Bacteria

GCSE OCR Gateway science, Biology, B6 - Beyond the Microscope, Bateria

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  • Created by: Lucy :)
  • Created on: 08-06-13 10:37

Bacteria info

  • cell wall keeps shape + stops bursting
  • strand of DNA in cytoplasm
  • ^ controls cell's activities + replication
  • sometimes several loops of DNA = plasmids
  • sometimes have a flagellum to help them move
  • come in 4 shapes: rods, curved rods, spheres + spirals
  • dif can survive in dif habitats as some comsume range of organic nutrients from their surroundings others produce their own
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Bacteria reproduction

  • asexual reproduction
  • each is a clone
  • binary fission = process in which they reproduce
  • they reproduce very quickly
  • ^ how sometimes you get ill as body can't respond quick enough
  • reproduce quicker when warm + good source of nutrients
  • ^ = need to store food carefully
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Culturing bacteria and aseptic technique

You can culture (grow) bacteria on an agar plate - a Petri dish containing agar jelly. Bacteria can be transferred to the plate from a sample using a wire inoculation loop.

It's important to use aseptic techniqye to protect yourself from infection and stop the agar from being contaminated by other microbes.

  • Wear gloves + keep long hair tied back
  • Sterilising equipment before + after use ( pass through bunsen burner)
  • Sealing the dish once you've transferred the bacteria onto it
  • Disposing of cultures safely after use - usually done by pressure sterilising in an autoclave
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Usefully using bacteria

How to make yoghurt:

  • sterilise equipment to kill off any unwanted microorganisms
  • pasterurise the milk (heat up to 72oC for 15 secs) - to kill "
  • let the milk cool
  • add a starter culture of Lactobacillus bacteria
  • incubate the mixture (heat to about 40oC) in a fermenter
  • The bacteria break down the lactose sugar in the milk into lactic acid
  • lactic acid causes the milk to clot + solidify into yoghurt
  • a sample is taken to see if it's the right consistency
  • flavours + colours are then sometimes added
  • then the yoghurt is packaged
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