Bacteria which often live in damp soil and convert nitrates into nitrogen gas are called?

• A. Nitrogen Fixing Bacteria
• B. Nitrification
• C. Denitrifying Bacteria
• D. Biodiversity

Answer: (C)

Denitrification is the process at work here. In damp, low-oxygen soils, certain bacteria use nitrate as an alternative to oxygen in their respiration and convert nitrate (NO3−) into nitrogen gas (N2) or nitrous oxide (N2O), which then escapes to the atmosphere. This is how nitrates are removed from soil or water and returned to air in the nitrogen cycle. That description specifically points to denitrifying bacteria.

Nitrogen-fixing bacteria, by contrast, convert atmospheric N2 into ammonia that organisms can use. Nitrification is the stepwise oxidation of ammonia to nitrite and then to nitrate. Biodiversity is a broad term about variety of life, not a microbial process.