Most human pathogens are ______ with regard to temperature range of tolerance for optimum growth.
A. thermophiles
B. mesophiles
C. psychrophiles
D. xerophiles
The correct answer and explanation is :
The correct answer is B. mesophiles.
Explanation:
Human pathogens are most commonly classified as mesophiles because they thrive in moderate temperature ranges, typically between 20°C and 45°C. This temperature range closely matches the human body temperature, which is approximately 37°C. These pathogens have adapted to live and proliferate in environments that are within the normal human body temperature or slightly below it, making mesophiles the dominant group of microorganisms responsible for causing diseases in humans.
Temperature Classification of Microorganisms:
- Thermophiles (A): These organisms thrive in high-temperature environments, typically between 45°C and 80°C. Thermophiles are often found in hot springs, compost piles, and other high-heat environments. They do not typically pose a risk to humans since their optimal growth temperature is much higher than the human body temperature.
- Mesophiles (B): These are organisms that grow best at moderate temperatures, usually ranging from 20°C to 45°C. Human pathogens fall into this category because they are adapted to the average body temperature of humans (around 37°C). Many bacteria, viruses, fungi, and other microorganisms that infect humans are mesophilic. This is why mesophiles are most commonly associated with causing infectious diseases in humans.
- Psychrophiles (C): These organisms grow best at low temperatures, typically between -5°C and 20°C. Psychrophiles are often found in cold environments, such as the Arctic or deep ocean waters. They are not typically associated with human infections, as their preferred growth temperature is much lower than the human body temperature.
- Xerophiles (D): These microorganisms are adapted to survive in dry environments, not necessarily based on temperature. They can tolerate low water availability and can survive in places like dry deserts or salted environments. While they are interesting from an environmental adaptation perspective, they are not the main category of pathogens that affect humans.
Given this information, mesophiles are the correct category for human pathogens as they are adapted to the temperature range that matches the human body’s conditions.
Comparison of the different temperature classifications of microorganisms.
Here is the diagram illustrating the different temperature classifications of microorganisms. It highlights the optimal temperature ranges for thermophiles, mesophiles, psychrophiles, and xerophiles. As mentioned earlier, mesophiles, which thrive around human body temperature (37°C), are the most common category of pathogens that affect humans.