A student heats an inoculating loop until it is red hot. The student immediately uses the loop to transfer bacteria to sterile agar. No colonies grow.
Which change would best address the likely cause while maintaining aseptic conditions?
Dip the loop into unsterilised water before collecting the bacterial sample.
Collect the bacterial sample before heating the loop until red hot.
Allow the loop to cool without touching anything before collecting bacteria.
Leave the culture dish uncovered while the loop cools after transfer.
45 exam-style questions on Edexcel GCSE Biology 5.3 Immune system and medicines, covering 5.3.1 The specific immune system, 5.3.2 Response to immunisation, 5.3.3 Advantages and disadvantages of immunisation, 5.3.4 Antibiotics and bacterial infections, 5.3.5 Aseptic techniques in culturing, 5.3.6 Cross-sectional areas of cultures, 5.3.7 Stages of developing new medicines, and 5.3.8 Production of monoclonal antibodies. Each one has a worked solution and a mark scheme showing where the marks go.