What is the optimal growth temperature for Yersinia pseudotuberculosis?

• A. 4-8°C
• B. 25-30°C
• C. 37°C
• D. 42°C

Answer: (B)

The organism that’s being tested grows best at moderate temperatures, where its enzymes work most efficiently and membranes maintain proper fluidity. Yersinia pseudotuberculosis is adapted to environmental and animal hosts rather than human fever conditions, so its optimal replication occurs around 25–30°C. At this range, metabolic processes proceed rapidly enough to support robust growth.

At very cold temperatures (4–8°C), metabolism slows dramatically, so growth is minimal. At human body temperature (37°C), growth can occur but is not as vigorous because some enzymes and overall cellular processes are not optimized for that heat. At even higher temperatures (like 42°C), proteins can begin to denature and growth is inhibited.

Thus, 25–30°C provides the conditions that maximize growth for this organism in culture, making it the best choice.