Correct.

Now practice calculating titres by using the data for the 42 minute samples:

Sample: 10-1 10-2 10-3 10-4 10-5 10-6
Free p.f.u: 140 plaques 15 plaques 1 plaque No plaques No plaques No plaques
Total p.f.u: Confluent phage plaques 330 plaques 34 plaques 8 plaques 3 plaques No plaques

Express your answer in terms of 'plaque forming units (pfu)/ml'
(i.e. number of plaques x dilution factor x 10).

Click on the correct answer below:

  1. FREE: 1.4 x 103 p.f.u. ml-1
    TOTAL: 3.3 x 104 p.f.u. ml-1

  2. FREE: 2.8 x 103 p.f.u. ml-1
    TOTAL: 6.6 x 104 p.f.u. ml-1

  3. FREE: 1.4 x 104 p.f.u. ml-1
    TOTAL: 3.3 x 105 p.f.u. ml-1

  4. FREE: 2.8 x 104 p.f.u. ml-1
    TOTAL: 6.6 x 105 p.f.u. ml-1

  5. FREE: 1.4 x 105 p.f.u. ml-1
    TOTAL: 3.3 x 106 p.f.u. ml-1

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