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Understanding antibiotic resistance
Understanding antibiotic resistance

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7.1 Back to the soil

Recent technological advances and innovations have allowed a much wider range of microbes to be cultured and novel species and new metabolites to be identified. For example, Activity 7 reveals how teixobactin was discovered in 2015 by a team of scientists in the USA who managed to isolate and culture a previously unidentified soil bacterium. Teixobactin is a new class of antibiotic which is active against Gram-negative but not Gram-positive bacteria (Ling et al., 2015).

Activity 7 Discovering teixobactin

Timing: Allow about 15 minutes

First, listen to the interview with Dr Kim Lewis, leader of the research team who discovered teixobactin.

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Audio 2 Discovery of teixobactin.
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Now put the steps below in the correct order to match the culturing technique described by Dr Lewis.

Using the following two lists, match each numbered item with the correct letter.

  1. Collect soil sample

  2. Mix diluted soil sample with agar

  3. Sandwich sample between semi-permeable membranes

  4. Place diffusion chamber in soil

  5. Remove diffusion chamber from soil

  6. Select colonies and grow in a Petri dish

  7. Screen for ability to make antibiotics

  8. Assess compounds for efficacy and usefulness

  • a.First

  • b.Fifth

  • c.Second

  • d.Fourth

  • e.Third

  • f.Eighth

  • g.Seventh

  • h.Sixth

The correct answers are:
  • 1 = a
  • 2 = c
  • 3 = e
  • 4 = d
  • 5 = b
  • 6 = h
  • 7 = g
  • 8 = f

What are the advantages of this new technique?


It re-creates the normal growing conditions of the bacteria, allowing them to be successfully cultivated. The recovery rate by this method is 50% compared with only 1% of cells from soil samples cultured on a Petri dish (Ling et al., 2015).