Bacteria play a crucial role in the nitrogen cycle by participating in various processes that convert nitrogen into forms usable by living organisms. Key roles include nitrogen fixation, where certain bacteria convert atmospheric nitrogen (N2) into ammonia (NH3), making it accessible for plants. Additionally, bacteria are involved in nitrification, converting ammonia into nitrates, and denitrification, returning nitrogen to the atmosphere. These microbial processes enhance soil fertility and maintain ecosystem health, making bacteria essential for sustaining life on Earth and supporting agricultural productivity.