M.luteus or E.coli

Discussion in 'Supporting Biology' started by Vitreous Humour, May 16, 2019 at 11:09 AM.

  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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