Which organisms carry out denitrification in the nitrogen cycle?

Denitrifying bacteria, including species from genera like Pseudomonas, Thiobacillus, and Clostridium, perform denitrification in the nitrogen cycle. These specialized microorganisms convert nitrates (NO₃⁻) and nitrites (NO₂⁻) in soil back into atmospheric nitrogen gas (N₂), completing the nitrogen cycle. Denitrification primarily occurs in oxygen-poor (anaerobic) conditions, such as waterlogged soils, wetlands, and aquatic sediments. While this process is essential for preventing excessive nitrate accumulation in ecosystems, it can also reduce soil fertility in agricultural systems by removing nitrogen that plants need. Understanding denitrification is crucial for managing agricultural practices, treating wastewater, and maintaining healthy aquatic ecosystems where nitrogen pollution can cause serious problems like algal blooms.