Isolation of Ammonia Oxidizing Bacteria

Ammonia oxidizing bacteria (AOB) oxidize ammonia to nitrate and play significant role in nitrogen cycle. Isolation and cultivation of AOB poses difficulty due to their complex requirement and slow growth rate, hence, culture independent methods are widely applied to study their presence in various ecosystems. In order to investigate basic physiology and to explore the potential of AOB, batch cultivation in laboratory is also necessary. Techniques for enrichment and isolation of AOB on solid media and in liquid media, like serial dilution method and dilution to extinction method, are discussed in the present chapter. To check the presence of AOB during their growth period, various parameters are monitored like utilization of ammonia, production of nitrate and/or nitrite, and presence of heterotrophs. Methods for their qualitative and quantitative estimation are also incorporated in the chapter.