Marine microbiologists are investigating the efficacy of three newly synthesized antimicrobial peptides (AP-1, AP-2, and AP-3) designed to combat a pathogenic strain of Vibrio harveyi in commercial shrimp hatcheries.
They inoculated an agar plate with V. harveyi and placed paper discs containing equal concentrations of the peptides onto the agar. They also included a control paper disc, labeled C-0, containing only sterile saline solution.
The plate was incubated, and the results are shown in the diagram below:
What is the purpose of the control paper disc C-0 in this investigation?
The diameter of the clear zone of inhibition around antimicrobial disc AP-1 is 26 mm.
Calculate the area of this zone of inhibition.
Use the equation:
Area=πr2 \text{Area} = \pi r^2 Area=πr2Take π≈3.142\pi \approx 3.142π≈3.142. Give your answer to 3 significant figures.
Following widespread prophylactic use of peptide AP-1 in shrimp farms over the next eighteen months, a new strain of V. harveyi emerged that was completely unaffected by AP-1. Suggest why peptide AP-1 no longer had an effect.