Which organisms thrive between 4°C and 25°C?

• A. Psychrophiles
• B. Psychrotrophs
• C. Mesophiles
• D. Halophiles

Answer: (B)

Temperature defines microbial growth groups, and psychrotrophs are the ones that fit this cool-to-mild range best. They can grow at refrigeration-like temperatures and also at moderate temperatures, with an optimum around room temperature (roughly 20–30°C). That flexibility lets them thrive in a window from about 4°C up to 25°C, which is exactly the range given.

Psychrophiles, by contrast, prefer consistently cold environments and struggle as temperatures rise toward 25°C. Mesophiles grow best at moderate temperatures and usually need temperatures a bit higher than 4°C, so 4°C is not ideal for them, even though they can handle around 25°C. Halophiles are defined by their salt tolerance, not their temperature range, so they aren’t defined by thriving specifically in this 4–25°C window.