The best method to isolate single colonies is the plate, and the best method to count colonies is the plate
a. streak, pour
b. defined, complex
c. complex, defined
d. spread, streak
e. pour, streak

option a. streak, pour

Explanation:

The best method to isolate single bacterial colonies is the "streak-plating" method.

The "streak-plate" procedure is used to isolate pure cultures of bacteria or also colonies, from mixed populations by mechanical separation. Millions of cells form a colony, they grow in a cluster on an agar plate. With this method, a mixture of cells is spread over the surface of a agar-based nutrient in a petri dish, that makes that less bacterial cells are deposited at widely separated point on the surface and, after incubation, they develop into colonies.

On the other hand, the best method to count colonies is the pour plate method. It helps to enumerate bacterial cells in a mixed sample, often used to count the number of microorganisms in those samples, which are added to a molten agar medium before its solidification occur. The result is colonies uniformly distributed throughout the solid medium when the appropriate sample dilution is plated.

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