2. To determine if the type of agar affects bacterial growth, a scientist cultures E. coli on four different types of agar. Five petri dishes are set up to collect results: One with nutrient agar and E. coli One with mannitol-salt agar and E.coli One with MacConkey agar and E.coli I One with LB agar and E. coli One with nutrient agar but NO E. coll . a. Independent Variable: b. Dependent Variable: c. Controls: MBAPO