Definition of: nitrobacterium

(nī′trō·bak·tir′ē·əm) noun plural ·ri·a (-ē·ə)
Any of various soil bacteria involved in the process of nitrification, especially the nitrous group (genus Nitrosomonas), which converts ammonia into nitrites, and the nitric group (genus Nitrobacter), which oxidizes nitrites into nitrates. Also nitric or nitrous bacterium.