In what environments might the following organisms be found?

1. hyperthermophile
2. thermophile
3. mesophile
4. psychrophile

1. hyperthermophile – deep sea vents heated by volcanic activity
2. thermophile – compost piles
3. mesophiles – most environments, e.g., human body, soil water systems
4. psychrophile – super cooled waters of the Arctic and Antarctic

Differentiate between psychrophile and psychrotroph

Psychrophiles grow best at low temperatures whereas psychrotrophs are mesophiles that are capable of growth at lower (e.g., refrigerator) temperatures.

Why are psychrotrophic bacteria of concern to those in the food-service industry?

Refrigeration is used to control spoilage microbes in food but psychrotrophs, such as Pseudomonas , are still capable of growth at these temperatures.

What is the optimum growth temperature for most human pathogens? Explain.

Most human pathogens grow best at 37°C, which is body temperature.

Name three cellular components involved in metabolism that are influenced by temperature changes, and explain the changes that occur to those components

Temperature affects metabolism by influencing enzymes, cell membranes, and ribosomes. Elevated temperatures denature proteins, disrupt membranes, and inhibit ribosome function.

Which has a greater impact on the survival of an organism, temperatures above its maximum temperature or temperatures below its minimum temperature? Explain why and how this relates to typical methods used to control microbial growth.

Elevated temperatures have the greatest impact because of destruction of essential molecules and function. Low temperatures are actually used to preserve microbial cultures. Low temperatures slow metabolism and are used to control growth.