Nitrite-oxidizing Bacteria: Cultivation, Growth Physiology, and Chemotaxonomy

Abstract

Nitrification is a microbial process that converts ammonia and similar nitrogen compounds into nitrite (NO2−) and then nitrate (NO3−) via two different functional groups of specialized chemolithoautotrophic microorganisms. In an oxygenic environment, nitrification occurs in rivers, lakes, aerated soil, ocean water, sediments, and biological wastewater treatment systems. The nitrite-oxidizing bacteria (NOB) can be divided into two groups: Nitrococcus and Nitrobacter. NOBs are comparatively easy to handle as they are adapted to high nitrite concentrations up to 29 mM. The NOB species are organic/chemoautotrophic bacteria, and most of them are Gram-negative. Due to the poor energy balance, the growth rate of NOBs and conversion of nitrite to nitrate are slow. The NOBs multiply in a broad range of environmental habitats, like terrestrial, marine, and acidic conditions, and they have diverse lifestyles (lithoautotrophic, mixotrophic, and heterotrophic). Nitrite oxidation is a strictly aerobic approach and the C-requirement may be met by the assimilation of CO2. The fatty acid profile will reflect the phylogenetic heterogeneity and studying it is a valuable chemotaxonomy method. Hence, knowing the importance of NOBs, it was necessary to compile all the available information. This chapter encompasses the cultivation, growth physiology, identification, and chemotaxonomy of NOBs.