REDUCING EMISSIONS OF THE GREENHOUSE GAS NITROUS OXIDE (N₂O) BY BACTERIA ISOLATED FROM WHEAT RHIZOSPHERE

Microbial dissimilatory nitrogen metabolism processes are among the main factors negatively affecting nitrogen availability to plants. These include nitrate respiration and denitrification, which result in reduction of plant-available N and emission of N₂O, a highly potent greenhouse gas. These activities are strongly enriched in the rhizosphere, stressing their environmental and agricultural importance. One approach to minimize these effects is inoculation of plants with active N₂O reducing bacteria and thus minimizing N₂O emissions from agricultural fields.

In this study, bacteria were isolated from wheat roots under anaerobic atmosphere, enriched with N₂O gas, in the presence and absence of nitrate. All together, five promising isolates were tested while only two of them have shown, higher N₂O reduction ability rather than nitrate reduction in aqueous medium. The two selected isolates were examined for their ability to reduce N₂O emission under anaerobic conditions from inoculated soil and wheat plants in presence of nitrate and combination of three sugars as carbon sources. Inoculation of one of the isolates to soil or soil planted with wheat, in presence of nitrate and carbon sources resulted in reduced release of N₂O to the atmosphere. Treatment with the other isolate, resulted in less pronounced N₂O reduction. This can be explained by the absence of nitrate reducing gene (Nar/Nap) in its genome and having a need for external N₂O for respiration. In the near future, we will validate the possibility to reduce N₂O emission under condition simulating agricultural field by co-inoculation of the two promising isolates. Reducing N₂O emission is a way to combat negative impacts of agricultural practices on the environment.