Barry is a student beginning his Honours year and needs to decide how to conduct a preliminary experiment on differentiating different strains of bacteria in a clinical sample.

a. What kind of media should Barry grow his cultures on? Include a rationale for your choice. (2)

b. Suggest a simple method of how Barry should separate strains of bacteria and produce pure cultures to study in this sample. (3)

c. Barry used a Gram stain to stain two distinctly different cultures in his pure incubated samples. Under the microscope one culture is pink whilst the other is purple; what does this indicate for Barry’s cultures, why does the same stain stain differently? (1+3)