Altering N2O emissions by manipulating wheat root bacterial community

Alla Usyskin-Tonne,Yitzhak Hadar,Dror Minz

doi:10.1038/s41598-019-44124-3

Alla Usyskin-Tonne, Yitzhak Hadar + Show 1 more

Open Access

https://doi.org/10.1038/s41598-019-44124-3

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Abstract

Nitrous oxide (N2O) is a greenhouse gas and a potent ozone-depleting substance in the stratosphere. Agricultural soils are one of the main global sources of N2O emissions, particularly from cereal fields due to their high areal coverage. The aim of this study was to isolate N2O-reducing bacteria able to mitigate N2O emissions from the soil after inoculation. We isolated several bacteria from wheat roots that were capable of N2O reduction in vitro and studied their genetic potential and activity under different environmental conditions. Three of these isolates- all carrying the nitrous oxide reductase-encoding clade I nosZ, able to reduce N2O in vitro, and efficient colonizers of wheat roots- presented different N2O-reduction strategies when growing in the root zone, possibly due to the different conditions in situ and their metabolic preferences. Each isolate seemed to prefer to operate at different altered oxygen levels. Isolate AU243 (related to Agrobacterium/Rhizobium) could reduce both nitrate and N2O and operated better at lower oxygen levels. Isolate AU14 (related to Alcaligenes faecalis), lacking nitrate reductases, operated better under less anoxic conditions. Isolate NT128 (related to Pseudomonas stutzeri) caused slightly increased N2O emissions under both anoxic and ambient conditions. These results therefore emphasize the importance of a deep understanding of soil–plant–microbe interactions when environmental application is being considered.

Highlights

Nitrous oxide (N2O) is a long-lived greenhouse gas that is ca. 300 times more active under absorbing infrared radiation than carbon dioxide per unit mass[1,2], as well as a potent ozone-depleting substance in the stratosphere[3]
Field-scale experiments to examine the possibility of mitigating N2O emissions from soybean were conducted by inoculation of nodules with N2O-reducing Bradyrhizobium diazoefficiens mutants[20], and with a mixed culture of indigenous symbiotic B. diazoefficiens strains[21]
Bacteria were isolated from wheat roots based on their ability to grow under anaerobic conditions, with N2O as sole electron acceptor and three carbon sources

Summary

Introduction

Nitrous oxide (N2O) is a long-lived greenhouse gas that is ca. 300 times more active under absorbing infrared radiation than carbon dioxide per unit mass[1,2], as well as a potent ozone-depleting substance in the stratosphere[3]. Field-scale experiments to examine the possibility of mitigating N2O emissions from soybean were conducted by inoculation of nodules with N2O-reducing Bradyrhizobium diazoefficiens mutants[20], and with a mixed culture of indigenous symbiotic B. diazoefficiens strains[21]. These last two studies concluded that using efficient native strains is more effective than using mutants. N2O emission was measured under both anoxic (nitrogen-flushed) and ambient atmosphere, to mimic a broad spectrum of soil conditions This novel approach to mitigating N2O emission from agricultural soils may provide an additional environmental tool in the fight against these harmful emissions

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