Life on N2O: deciphering the ecophysiology of N2O respiring bacterial communities in a continuous culture

• Published in: The ISME Journal 2018-04, Vol.12 (4), p.1142-1153
• Main Authors: Conthe, Monica, Wittorf, Lea, Kuenen, J. Gijs, Kleerebezem, Robbert, van Loosdrecht, Mark C. M., Hallin, Sara
• Format: Article
• Language: English
• Subjects: 14/32; 45/77; 631/326/2565; 631/443; Acetic acid; Bacteria; Biomedical and Life Sciences; Coding; Communities; Community composition; Continuous culture; Culture; Cytotoxicity; Dilution; Ecology; Ecophysiology; Evolutionary Biology; Greenhouse effect; Greenhouse gases; Growth rate; Life Sciences; Microbial Ecology; Microbial Genetics and Genomics; Microbiology; Microorganisms; Mikrobiologi; Nitrous oxide; Phylogeny; Reductase; Reduction
• ISSN: 1751-7362; 1751-7370; 1751-7370
• DOI: 10.1038/s41396-018-0063-7

Reduction of the greenhouse gas N 2 O to N 2 is a trait among denitrifying and non-denitrifying microorganisms having an N 2 O reductase, encoded by nosZ . The nosZ phylogeny has two major clades, I and II, and physiological differences among organisms within the clades may affect N 2 O emissions from ecosystems. To increase our understanding of the ecophysiology of N 2 O reducers, we determined the thermodynamic growth efficiency of N 2 O reduction and the selection of N 2 O reducers under N 2 O- or acetate-limiting conditions in a continuous culture enriched from a natural community with N 2 O as electron acceptor and acetate as electron donor. The biomass yields were higher during N 2 O limitation, irrespective of dilution rate and community composition. The former was corroborated in a continuous culture of Pseudomonas stutzeri and was potentially due to cytotoxic effects of surplus N 2 O. Denitrifiers were favored over non-denitrifying N 2 O reducers under all conditions and Proteobacteria harboring clade I nosZ dominated. The abundance of nosZ clade II increased when allowing for lower growth rates, but bacteria with nosZ clade I had a higher affinity for N 2 O, as defined by μ max / K s . Thus, the specific growth rate is likely a key factor determining the composition of communities living on N 2 O respiration under growth-limited conditions.