N. alkalicus N. hamburgensis N. vulgaris N. winogradskyi Nitrobacter is a genus comprising rod-shaped, gram-negative, and chemoautotrophic bacteria.

[1] Nitrobacter play an important role in the nitrogen cycle by oxidizing nitrite into nitrate in soil and marine systems.

[8] Before 2004, nitrite oxidation was believed to only occur within Pseudomonadota; it is likely that further scientific inquiry will expand the list of known nitrite-oxidizing species.

The production of nitrate (NO3−) by oxidation of nitrite (NO2−) is accomplished by nitrification - the process that produces the inorganic nitrogen that meets much of the demand of marine oxygenic, photosynthetic organisms such as phytoplankton, particularly in areas of upwelling.

For this reason, nitrification supplies much of the nitrogen that fuels planktonic primary production in the world's oceans.

[12] These values indicate that it would be energetically favourable for an organism to carry out complete nitrification from ammonia to nitrate (comammox), rather than conduct only one of the two steps.

In 2015, it was discovered that the species Nitrospira inopinata possesses all the enzymes required for carrying out complete nitrification in one step, suggesting that this reaction does occur.

Chemoorganotroph growth is slow and unbalanced, thus more poly-β-hydroxybutyrate granules are seen that distort the shape and size of the cells.

[1][18] Since all members in the genus Nitrobacter are obligate aerobes, oxygen along with phosphorus tend to be factors that limit their capability to perform nitrite oxidation.

[1] One of the major impacts of nitrifying bacteria such as ammonia-oxidizing Nitrosomonas and nitrite-oxidizing Nitrobacter in both oceanic and terrestrial ecosystems is on the process of eutrophication.

[20] A follow-up study performed by Navarro et al. (1995) showed that various Nitrobacter populations carry two large plasmids.

[19] In conjunction with Schutts’ (1990) study, Navarro et al. (1995) illustrated genomic features that may play crucial roles in determining the distribution and ecological impact of members of the genus Nitrobacter.

[1] In 1890, Ukrainian-Russian microbiologist Sergei Winogradsky isolated the first pure cultures of nitrifying bacteria which are capable of growth in the absence of organic matter and sunlight.

[22] In 1891, English chemist Robert Warington proposed a two-stage mechanism for nitrification, mediated by two distinct genera of bacteria.

[23] Winogradsky named the bacteria responsible for the oxidation of nitrite to nitrate Nitrobacter in his subsequent study on microbial nitrification in 1892.