Question

Which one of the following statements is not true about the heat resistance of vegetative cells of bacteria?

• A. Thermophiles are more resistant to heat.
• B. Bacteria forming clumps or capsules are more difficult to kill.
• C. Bacterial cells high in lipid are harder to kill.
• D. Rods are usually more resistant to heat than cocci.

Hint:

Among non-spore-forming vegetative pathogens, the coccus Staphylococcus aureus exhibits higher heat tolerance than many rod-shaped vegetative bacteria.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The heat resistance of vegetative bacterial cells is influenced by cell morphology, lipid content, clustering, and physiological temperature classification.

Step 2: Detailed Explanation:
- Statement (A) is true: Thermophilic bacteria are adapted to high temperatures and have high vegetative heat resistance.
- Statement (B) is true: Clumping or capsule formation provides physical protection, making cells harder to kill.
- Statement (C) is true: Intracellular lipids provide insulation, increasing heat resistance.
- Statement (D) is false: Generally, spherical bacteria (cocci) are more resistant to heat than non-spore-forming rod-shaped bacteria (rods) due to their smaller surface-to-volume ratio and dense cell wall structures. Therefore, statement (D) is not true.

Step 3: Final Answer:
The incorrect statement is that rods are more resistant to heat than cocci.