Distinguish growth inhibition from bacterial killing, interpret antibiotic experiments and explain treatment of bacterial disease and effects on gut flora using marked questions.
Aquaculture is the controlled cultivation of aquatic organisms such as fish, shellfish and plants. It is an important source of food in many countries of the world. The photograph shows freshwater aquaculture ponds in Africa.
Vibrio are bacteria that are common in aquatic habitats. They cause diarrhoea and cholera and are also pathogenic to shellfish. The resistance of Vibrio to antibiotics and to heavy metals in aquaculture ponds in Nigeria was investigated.
The samples of Vibrio taken from each pond were spread on agar containing different antibiotics.
Some of the antibiotics used were bacteriostatic and some were bactericidal. State the difference between a bacteriostatic antibiotic and a bactericidal antibiotic.
The method did not distinguish between bacteriostatic and bactericidal antibiotics because no colonies grew. Suggest how the method would need to be modified to show which antibiotics were bacteriostatic and which were bactericidal. Give a reason for your answer.