What are the external factors that affect microbial growth and describe how is each factor is used to classify microbes?

Cultivation of microbes is the basic technique in Microbiology that enables the growth of microbes in culture. Growing microbes in culture allow Microbiologists to study the colony morphology, isolate a pure culture, and to understand the growth characteristics of an organism. For this discussion post, students are expected to write a minimum 250 word essay on the factors that affect the growth of bacteria. In your essay, address the following topics

What are the external factors that affect microbial growth and describe how is each factor is used to classify microbes? (For example, microbes that grow in acidic pH are called acidophiles)
What are selective and differential media? Give 2 examples for each. Explain in detail how selective and differential media can be used to diagnose and identify microbes.
What are the various techniques used to isolate pure cultures of bacteria? Explain in detail.