A common mechanism for efficient N 2 O reduction in diverse isolates of nodule‐forming bradyrhizobia

Mania, D and Woliy, K and Degefu, T and Frostegård, A (2019) A common mechanism for efficient N 2 O reduction in diverse isolates of nodule‐forming bradyrhizobia. Environmental Microbiology (TSI). pp. 1-15. ISSN 1462-2912

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Abstract

Bradyrhizobia are abundant soil bacteria, which can form nitrogen‐fixing symbioses with leguminous plants, including important crops such as soybean, cowpea and peanut. Many bradyrhizobia can denitrify, but studies have hitherto focused on a few model organisms. We screened 39 diverse Bradyrhizobium strains, isolated from legume nodules. Half of them were unable to reduce N2O, making them sources of this greenhouse gas. Most others could denitrify NO3‐ to N2. Time‐resolved gas kinetics and transcription analyses during transition to anaerobic respiration revealed a common regulation of nirK, norCB and nosZ (encoding NO2‐, NO and N2O reductases), and differing regulation of napAB (encoding periplasmic NO3‐ reductase). A prominent feature in all N2‐producing strains was a virtually complete hampering of NO3‐ reduction in presence of N2O. In‐depth analyses suggest that this was due to a competition between electron transport pathways, strongly favouring N2O over NO3‐ reduction. In a natural context, bacteria with this feature would preferentially reduce available N2O, produced by themselves or other soil bacteria, making them powerful sinks for this greenhouse gas. One way to augment such populations in agricultural soils is to develop inoculants for legume crops with dual capabilities of efficient N2‐fixation and efficient N2O reduction.

Item Type:	Article
Divisions:	Research Program : East & Southern Africa
CRP:	UNSPECIFIED
Uncontrolled Keywords:	Bradyrhizobia, N2O reduction, N2‐fixation, soil bacteria, greenhouse gas, Rhizobia
Subjects:	Others > Soil Science
Depositing User:	Mr Ramesh K
Date Deposited:	10 Jul 2019 04:43
Last Modified:	02 Aug 2019 03:34
URI:	http://oar.icrisat.org/id/eprint/11146
Official URL:	https://doi.org/10.1111/1462-2920.14731
Projects:	UNSPECIFIED
Funders:	UNSPECIFIED
Acknowledgement:	We thank Linda Bergaust for the genome sequencing and data treatment. This work was in parts financed by PASUSI within the ERA‐NET Co‐fund Horizon2020 program Leap‐Agri, under the EC Grant agreement No. 727715 and Research Council of Norway project No. 290488. K. Woliy was supported by a grant from the Norwegian State Educational Loan Fund.
Links:	Google Scholar

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