Ecophysiology of nitrite-oxidizing bacteria

The elusive and still barely studied nitrite-oxidizing bacteria (NOB) catalyze the second step of nitrification and are the Big Unknown of the nitrogen cycle. Our aim is to elucidate the biology and functional roles of NOB in natural environments and engineered systems like wastewater treatment facilities. To achieve this, we analyze their (meta)genomes and validate genome-based hypotheses through laboratory experiments. 

Historically, NOB were viewed as highly specialized with limited metabolic capabilities, but recent findings challenge this perception. Our research has revealed unexpected physiological traits in NOB that extend beyond nitrification, highlighting their diverse ecological functions. For instance, Nitrospira moscoviensis, representing the environmentally most widespread and diverse NOB lineage, can utilize hydrogen gas (H2) as its sole energy source and electron donor through the oxyhydrogen ('Knallgas') reaction. Remarkably, N. moscoviensis can extract atmospheric H2 to fuel its metabolism due to its extremely high affinity for H2. Furthermore, several NOB exhibit remarkable metabolic versatility. They are capable of oxidizing both nitrite and formate, and can use both oxygen and nitrate as terminal electron acceptors.

 

Selected publications on this topic:
  • Leung PM, Daebeler A, Chiri E, Hanchapola I, Gillett DL, Schittenhelm RB, Daims H, Greening C. 2022. A nitrite-oxidising bacterium constitutively consumes atmospheric hydrogen. ISME J. 16: 2213-2219 https://doi.org/10.1038/s41396-022-01265-0
  • Daebeler A, Kitzinger K, Koch H, Herbold CW, Steinfeder M, Schwarz J, Zechmeister T, Karst SM, Albertsen M, Nielsen PH, Wagner M, Daims H. 2020. Exploring the upper pH limits of nitrite oxidation: diversity, ecophysiology, and adaptive traits of haloalkalitolerant Nitrospira. ISME J. 12: 2967-2979 https://doi.org/10.1038/s41396-020-0724-1
  • Daims H, Lücker S, Wagner M. 2016. A new perspective on microbes formerly known as nitrite-oxidizing bacteria. Trends Microbiol. 24: 699-712 https://doi.org/10.1016/j.tim.2016.05.004
  • Koch H, Lücker S, Albertsen M, Kitzinger K, Herbold C, Spieck E, Nielsen PH, Wagner M, Daims H. 2015. Expanded metabolic versatility of ubiquitous nitrite-oxidizing bacteria from the genus Nitrospira. Proc. Natl. Acad. Sci. USA 112: 11371-11376 https://doi.org/10.1073/pnas.1506533112
  • Koch H, Galushko A, Albertsen M, Schintlmeister A, Gruber-Dorninger C, Lücker S, Pelletier E, Le Paslier D, Spieck E, Richter A, Nielsen PH, Wagner M, Daims H. 2014. Growth of nitrite-oxidizing bacteria by aerobic hydrogen oxidation. Science 345: 1052-1054 https://doi.org/10.1126/science.1256985
  • Lücker S, Wagner M, Maixner F, Pelletier E, Koch H, Vacherie B, Rattei T, Sinninghe Damsté JS, Spieck E, Le Paslier D, Daims H. 2010. A Nitrospira metagenome illuminates the physiology and evolution of globally important nitrite-oxidizing bacteria. Proc. Natl. Acad. Sci. USA 107: 13479-13484 https://doi.org/10.1073/pnas.1003860107