Nitrifying Proteobacteria

Nitrifying Proteobacteria

This group comprises aerobic Gram-negative chemolithoautotrophs that derive their energy from the oxidation of inorganic nitrogen compounds (either ammonia or nitrite), and their carbon from CO2. The nitrifying bacteria are represented in both the Î±- and Î²-Proteobacteria.

The oxidation of ammonia through to nitrate is a two-stage process, with specific bacteria carrying out each stage (ammonia to nitrite and nitrite to nitrate). This is reflected in the generic names of the bacteria, bearing the prefix Nitroso- or Nitro-according to whether they carry out the first or second reaction. Nitrifying bacteria play an essential role in the cycling of nitrogen in terrestrial, marine and freshwater habitats. Nitrite, which is toxic to many forms of life, rarely accumulates in the environment, due to the activity of the Nitrobacteria. As was the case with the purple photosynthetic bacteria, several cell forms are represented among the nitrifiers.

Representative genera: Nitrosomonas (NH4+ âˆ’−−−−→ NO2−)

Nitrobacter  (NO2−−−−−−→NO3−)