Putrefying bacteria act upon:

a. Fats

b. Carbohydrates

c. Protein

d. Starch

Role of Putrefying Bacteria in Decomposition

• Putrefying bacteria act on proteins, using them as their primary energy source.
• They break down dead organic matter through an anaerobic pathway, releasing toxic gases that contribute to the degradation of the body parts of dead organisms.

Nitrogen Cycle Connection

• During decomposition, putrefying bacteria release ammonium ions (NH₄⁺).
• These ammonium ions are converted into nitrates (NO₃⁻) by specialized microbes called nitrifying bacteria.
• Plants then absorb these nitrates as nutrients.
• In this way, nitrogen from dead matter is recycled back into the environment, ensuring the continuity of the nitrogen cycle.

Thus, putrefying bacteria play a dual role: breaking down dead matter and enabling the recycling of nitrogen through collaboration with nitrifying bacteria.

So, the correct answer is option (C).