My first objective within the NORA network was to perform an isolation project and create a biobank of bacteria involved in nitrogen cycle in soil, covering a wide taxonomic and functional diversity. From the biobank we have chosen strains of contrasting, end-point analysis based phenotypes performing full-fledged denitrification (step-wise nitrate to dinitrogen gas reduction) and those missing the last step of the pathway (nitrous oxide reduction to dinitrogen gas) potentially contributing to N2O emission. We have analyzed DRPs (Denitrification Regulatory Phenotypes ) in response to certain environmental conditions (e.g. nitrate / nitrite / oxygen concentrations, pH) and confronted with genes (denitrification functional genes sequencing) of these organisms. Rhodanobacter sp., a representative of Xanthomonadaceae family, widespread soil organisms carrying nosZ gene encoding nitrous oxide reductase is not able to reduce N2O under low pH conditions. Previous lab experiments with Paracoccus denitrificans, a model organism in denitrification show that nosZ is being transcribed under low pH, but function of the enzyme is missing . Our results are to be in favour, that, although there is a genetic potential for full-fledged denitrification, the environment selects for functions. The mystery of missing N2O reductase activity under low pH conditions will be further investigated…
Waste water adventure
In April / May 2015 we have been hosting Monica Conthe (NORA fellow from TU Delft, NL) and Aline Ramos (NORA fellow from Bioclear, NL) at NMBU in Ås, NO. Both Monica and Aline work with waste water treatment and I had a great pleasure to join the project investigating the fate of N2O in different waste water management systems. Is denitrification in WWT a source for N2O emission or maybe a sink for it? I invite you to read Monica’s summary.
1. Bergaust, L., L.R. Bakken, and A. Frostegard, Denitrification regulatory phenotype, a new term for the characterization of denitrifying bacteria. Biochemical Society Transactions, 2011. 39: p. 207-212.
2. Bergaust, L., et al., Denitrification Response Patterns during the Transition to Anoxic Respiration and Posttranscriptional Effects of Suboptimal pH on Nitrous Oxide Reductase in Paracoccus denitrificans (vol 76, pg 6387, 2010). Applied and Environmental Microbiology, 2010. 76(24): p. 8285-8285.