Nitrosomonadales

The Nitrosomonadales are a small order of Proteobacteria. Like all Proteobacteria, they are Gram-negative. They include Nitrosomonas, Nitrosospira, Gallionella (iron bacteria), and Spirillum. Members of the genus Nitrosomonas oxidize ammonia into nitrite, a process called nitrification. They are important in the nitrogen cycle. The species Spirillum minus causes rat-bite fever.