Question

The optimum temperature for rapid growth of mesophiles is:

• A. \( 40^\circ C \text{ to } 50^\circ C \)
• B. \( 50^\circ C \text{ to } 60^\circ C \)
• C. \( 15^\circ C \text{ to } 20^\circ C \)
• D. \( 25^\circ C \text{ to } 40^\circ C \)

Hint:

Microorganisms are classified by their optimum growth temperatures: 
- Psychrophiles: \( -5^\circ C \) to \( 15^\circ C \). 
- Mesophiles: \( 20^\circ C \) to \( 45^\circ C \). 
- Thermophiles: \( 45^\circ C \) to \( 80^\circ C \). 
Understanding these classifications helps in microbiology and industrial processes.

Answer 1

The Correct Option is D

Microbes are grouped into three broad temperature classes based on where they grow best, cold-loving, moderate, and heat-loving. Placing mesophiles correctly among these classes points to the right range.

1. \( 40^{\circ}C \) to \( 50^{\circ}C \): Already edging into the warmer end reserved for heat-tolerant organisms rather than typical moderate-temperature microbes.
2. \( 50^{\circ}C \) to \( 60^{\circ}C \): A clearly thermophilic range, suited to organisms found in hot springs and compost piles, not mesophiles.
3. \( 15^{\circ}C \) to \( 20^{\circ}C \): Sits in psychrophile territory, the cold-adapted group, too low for mesophiles to grow at their best rate.
4. \( 25^{\circ}C \) to \( 40^{\circ}C \): The moderate band that gives mesophiles, including most bacteria found in soil, water, and the human body, their fastest growth, since it comfortably includes body temperature around \( 37^{\circ}C \).

Since mesophiles are the "moderate temperature" class by definition, sitting between the cold-loving and heat-loving groups, their optimum growth range has to be the 25 to 40 degree Celsius band. The correct answer is \( 25^{\circ}C \) to \( 40^{\circ}C \).