RP6- Bacteria culture + antibodies

Question 1

Explain the purpose of boiling the agar. (1)

Answer 1

prevents contamination

Question 2

Explain the purpose of transferring the same volume of liquid culture onto each agar plate. (1)

Answer 2

same no. of bacteria –> allows comparison

Question 3

The oxidation of ammonia by nitrifying bacteria involves the enzyme ammonia monooxygenase. Each species of nitrifying bacteria has its own specific amoA gene that codes for production of ammonia monooxygenase.
In a second investigation, the scientists determined the expression of the amoA gene in two species of bacteria, S and T. Species S was from acid soil and species T was from soil with a neutral pH.
The scientists grew cultures of each species separately in soils of different pH.
They determined the amount of mRNA from the amoA gene in each culture.
The scientists set up their cultures in sterile glass bottles.
Suggest one suitable method for sterilising the bottles and explain why it was necessary to sterilise them. (2)

Answer 3

• steam/ wash in disinfectant/ alcohol
• kill other bacteria that might break down ammonia
• x flaming!!!

Question 4

A student investigated the effect of two antibiotics on the growth of a bacterium.
The bacterium is not resistant to chloramphenicol.
Suggest two reaons why the bacteria were able to grow in the culture containing chloramphenicol. (2)

Answer 4

1. too dilute
2. contamination w/ other (resistant) bacteria
3. mutation occurred