Nitrous oxide emission potentials of <i>Burkholderia</i> species isolated from the leaves of a boreal peat moss <i>Sphagnum fuscum</i><sup>*</sup>
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Using a culture-based nitrous oxide (N<sub>2</sub>O) emission assay, three active N<sub>2</sub>O emitters were isolated from <i>Sphagnum fuscum</i> leaves and all identified as members of <i>Burkholderia</i>. These isolates showed N<sub>2</sub>O emission in the medium supplemented with but not with , and <i>Burkholderia</i> sp. SF-E2 showed the most efficient N<sub>2</sub>O emission (0.20 μg·vial<sup>−1</sup>·day<sup>−1</sup>) at 1.0 mM KNO<sub>3</sub>. In <i>Burkholderia</i> sp. SF-E2, the optimum pH for N<sub>2</sub>O production was 5.0, close to that of the phyllosphere of <i>Sphagnum</i> mosses, while the optimum temperature was uniquely over 30 °C. The stimulating effect of additional 1.5 mM sucrose on N<sub>2</sub>O emission was ignorable, but <i>Burkholderia</i> sp<i>.</i> SF-E2 upon exposure to 100 mg·L<sup>−1</sup> <i>E</i>-caffeic acid showed uniquely 67-fold higher N<sub>2</sub>O emission. All of the three N<sub>2</sub>O emitters were negative in both acetylene inhibition assay and PCR assay for <i>nosZ</i>-detection, suggesting that N<sub>2</sub>O reductase or the gene itself is missing in the N<sub>2</sub>O-emitting <i>Burkholderia</i>. Upon exposure to <i>E</i>-caffeic acid often contained in <i>Sphagnum</i> mosses, N<sub>2</sub>O emission by <i>Burkholderia</i> sp. SF-E2 that was isolated as an epiphyte of <i>Sphagnum fuscum</i> was highly accelerated.
