To examine the characteristic of denitrification in Frankia, a symbiotic nitrogen-fixing microbe associated with non-leguminous plants, and its role as a N2O source or sink, Casuarina root nodule endophyte Frankia was isolated using sectioning method, which was then purely cultured to investigate the denitrification process under NO3- addition. The results showed that after addition of NO3- to the medium under anaerobic condition, the concentration of NO3- decreased with time, while the concentrations of NO2- and N2O initially increased and then decreased over time. Key denitrification genes and nitrogenase gene were detected at 26 h, 54 h and 98 h during incubation. Abundances of these genes significantly differed among each other, and their dynamics were asynchronous. Redundancy analysis of the effect of NO3-, NO2-, N2O concentrations on abundances of denitrification genes and nitrogenase gene indicated that 81.9% of the total variation in gene abundances could be explained by the first two axes. Frankia had a denitrifying activity under anaerobic condition, with denitrification genes, including nitrous oxide reductase gene (nosZ), being identified. Our results suggested that Frankia possessed a complete denitrification pathway and the ability of N2O reduction under anaerobic condition.
为了解非豆科植物共生固氮菌弗兰克氏菌的反硝化作用特点以及作为N2O源汇的能力,采用切片法分离并纯培养木麻黄根瘤内生弗兰克氏菌,探究NO3-添加下弗兰克氏菌的反硝化作用过程。结果表明:在厌氧培养条件下添加NO3-后,NO3-浓度随时间的增加而降低,26 h后趋于平稳;而NO2-和N2O的浓度随着时间的增加先升高后降低。在培养第26、54和98小时均检测到关键反硝化基因和固氮酶基因。基因之间的丰度差异显著,且随时间的变化不同步。冗余分析表明,以NO3-、NO2-和N2O浓度为解释变量,前2个排序轴总共解释了反硝化及固氮酶基因丰度总变异的81.9%。弗兰克氏菌在厌氧条件下具有反硝化作用,检测到系列反硝化基因,包括N2O还原酶基因(nosZ),表明该弗兰克氏菌具备完全的反硝化途径,具有还原吸收N2O的能力。.
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