M.luteus or E.coli

Discussion in 'Supporting Biology' started by Vitreous Humour, May 16, 2019.

  1. Hi

    Micrococcus luteus and Escherichia coli (the K12 strain). Both of these are suggested to be used in the practical 'Effects of Antibiotics on Bacteria'. Do you find there is a better result using one of these over the other?

    Thank you
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  2. I tend to use E.coli - for some reason we get the B strain but it still works. I find it reliably subcultures into broth and it goes nice and cloudy quickly. Always useful for last minute requests! The practical we do calls for 3 different discs so I usually give 2 different strengths of penicillin and a streptomycin. You tend to see consistently different size zones clear around the discs so you can tell which antibiotic works best (not that i can remember at the moment whether this was penicillin or streptomycin).
    Vitreous Humour likes this.
  3. I prefer M. Luteus a lot easier for the students to see
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  4. E.coli B tends to be used for studying phage sensitivity, restriction-modification, and protein expression.;)
  5. agree, nice & yellow, zones of inhibition easy to see.
  6. Nice answers.

    Also, how long should a bacteria be left to grow in the nutrient broth before I can use it to lawn an agar plate?

    Thank you
  7. I personally like B Megaterium if it's just antispetic zones of inhibition you're looking for. Very reliable, quick growing, creates a nice even lawn.
  8. I put it in overnight usually and this works
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  9. Ah ok that's good because I only transferred it 24 hours ago. I was told elsewhere the introduction of the bacteria to the broth has to be 4 days prior to the lawning so it has enough time to grow so the students can see enough of the bacterium in the broth.
  10. 4 days is far too long the culure, if Gram -ve will have been in the death phase and if Gram+ve will enter the sporulation phase.:);) This growth curve is for Bacillus.
    Vitreous Humour likes this.
  11. yeah George is right...you need it to be in the log phase of growth which is about 18 - 24 hours after innoculation....
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