Question

Which of the following types of bacteria does Pseudomonas belong to?

• A. Mesophilic bacteria
• B. Psychrotrophic bacteria
• C. Thermophilic bacteria
• D. Aerobic spore forming bacteria

Hint:

Whenever you see Pseudomonas in a dairy context, associate it immediately with psychrotropic contamination and post-pasteurization spoilage in refrigerated milk.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Bacteria are classified into different groups based on their optimum, minimum, and maximum growth temperatures. This classification helps identify potential spoilage organisms in cold-stored dairy products.

Step 2: Detailed Explanation:
- Psychrotrophic Bacteria: These organisms can grow and multiply at refrigeration temperatures (\(7^{\circ}\text{C}\) or below), even though their optimum growth temperature is higher (\(20^{\circ}\text{C}\) to \(30^{\circ}\text{C}\)).
- The genus Pseudomonas (specifically Pseudomonas fluorescens and Pseudomonas fragi) is the most common psychrotrophic contaminant in raw milk. These bacteria produce heat-stable enzymes that cause spoilage during cold storage.
- They are not thermophilic (heat-loving), do not form endospores, and their ability to grow at low temperatures distinguishes them from typical mesophiles.

Step 3: Final Answer
The genus Pseudomonas belongs to the category of psychrotrophic bacteria.