Step 1: Understanding the Concept:
Microorganisms are classified by their preferred temperature range into psychrophiles, mesophiles and thermophiles, and mesophiles are the moderate-temperature group that includes most bacteria relevant to human disease.
Step 2: Key Concept or Approach:
Place each temperature range on the psychrophile to thermophile scale and pick the one that matches a moderate range, since that is what mesophile means.
Step 3: Detailed Explanation:
15 to 20 °C is on the cool end, closer to psychrophilic organisms, not mesophiles.
40 to 50 °C and 50 to 60 °C both sit in the warm to hot range associated with thermophiles, well above what mesophiles need for their fastest growth.
25 to 40 °C sits right in the moderate zone, covering both typical room temperature and the human body temperature of about 37 °C, which is exactly where mesophiles, including many pathogens that infect humans, grow the fastest.
Step 4: Final Answer:
The optimum temperature range for rapid mesophile growth is 25 to 40 °C.