Final answer:
Nitrite helps confirm the presence of gram-negative bacteria and is involved in the nitrogen cycle.
Step-by-step explanation:
Nitrite helps confirm the presence of gram-negative bacteria. Gram-negative bacteria metabolize nitrate into nitrite, and the presence of nitrite in the urine is indirect evidence of infection. Additionally, nitrifying bacteria, such as those in the genus Nitrosomonas, oxidize ammonia to nitrite as part of the nitrogen cycle.