Some bacteria remain metabolically active in hot springs at temperatures above $60°C$. These bacteria are best classified as which type based on temperature requirements for growth?

• A. Psychrophiles
• B. Mesophiles
• C. Obligate anaerobes
• D. Thermophiles

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the temperature ranges associated with different bacterial classifications based on their optimal growth temperatures. Psychrophiles thrive in cold environments, typically below 15°C.
2. Step 2: Recognize that mesophiles prefer moderate temperatures, usually between 20°C and 45°C, which is typical for many human pathogens.
3. Step 3: Note that obligate anaerobes are classified based on oxygen requirements, not temperature, so this category is unrelated to temperature-based classification.
4. Step 4: Identify that bacteria thriving at temperatures above 60°C are classified as thermophiles, which are adapted to high-temperature environments such as hot springs.
5. Step 5: Conclude that since the bacteria remain metabolically active above 60°C, they fit the definition of thermophiles based on their temperature requirements for growth.