Complete Nitrifiers of the Genus Nitrospira (Comammox)

Since the first description of nitrifying microbes more than 100 years ago by Sergei Winogradsky nitrification was always thought to be conducted by the joint activity of two groups of microorganisms - the ammonia- and the nitrite-oxidizers. We recently discovered together with the group of Holger Daims that complete nitrifiers exist that can oxidize as single microorganisms ammonia to nitrate. These so-called Comammox (complete ammonia oxidizers) microorganisms are members of the genus Nitrospira and are widespread in terrestrial and freshwater habitats (Daims et al. 2015, Nature). In collaboration with Dr. Elena Lebedeva we obtained a pure culture from our Comammox enrichment and named it Nitrospira inopinata. Kinetic characterization of this comammox strain demonstrated that it has a higher affinity for ammonia than all studied ammonia-oxidizing bacteria (AOB) and most ammonia-oxidizing archaea (AOA). In contrast, its affinity for nitrite is rather low. Excitingly, N. inopinata has the highest biomass yield per mol of substrate oxidized among all nitrifiers analyzed. These results demonstrate that N. inopinata is very well adapted to oligotrophic conditions and that the comammox metabolism is highly efficient (Kits et al. 2017, Nature). In comparison to AOB, N. inopinata forms only very little N₂O at low oxygen conditions and can thus be considered a "green nitrifier" (Kits et al. 2019; Nature Communications). Future research on the fascinating comammox organisms in our team will focus on revealing which environmental parameters select for comammox microbes in agricultural soil and wastewater treatment plants in order to pave the way for targeted manipulation of such nitriying communities. Furthermore, we plan to perform detailed strutural and functional characterization of the very unsusual complexes I and IV in the respiratory chain of comammox microbes in order to better understand the unusual physiology of these microbes.

Now working on this theme: Chris Sedlaceck, Márton Palatinszky, Man-Young Jung (previously Mario Pogoda, Julia Vierheilig, Dimitri Kits, Ping Han)

Collaboration partners: Elena Lebedeva (Russian Academy of Sciences), Mads Albertsen, Per Nielsen (Aalborg University, Denmark), Nico Jehmlich, Martin van Bergen (UFZ, Leipzig, Germany), Bernd Bendinger (TU Hamburg, Germany), Lisa Stein (University of Alberta, Canada)

Selected publications on this theme:

Daims H, Lebedeva EV, Pjevac P, Han P, Herbold C, Albertsen M, Jehmlich N, Palatinszky M, Vierheilig J, Bulaev A, Kirkegaard RH, von Bergen M, Rattei T, Bendinger B, Nielsen PH, Wagner M. 2015. Complete nitrification by Nitrospira bacteria. Nature, 528: 504-509.

Kits KD, Sedlacek CJ, Lebedeva EV, Han P, Bulaev A, Pjevac P, Daebeler A, Romano S, Albertsen M, Stein LY, Daims H, Wagner M. 2017. Kinetic analysis of a complete nitrifier reveals an oligotrophic lifestyle Nature, 549: 269-272.

Kits KD, Jung MY, Vierheilig J, Pjevac P, Sedlacek CJ, Liu S, Herbold C, Stein LY, Richter A, Wissel H, Brüggemann N, Wagner M, Daims H. 2019. Low yield and abiotic origin of N₂O formed by the complete nitrifier Nitrospira inopinata. Nat Commun, 1: 1836.