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在厌氧条件下,以亚硝酸盐作为电子受体将甲烷氧化的反硝化厌氧甲烷氧化反应(nitrite-dependent anaerobic methane-oxidizing,n-damo)的发现,彻底颠覆了人们对甲烷循环的传统理解.通过分子生物学方法及13C和15N稳定同位素示踪技术,对河北省北澧河附近的旱地农田土壤(0~1 m)中n-damo菌的群落结构、丰度和活性进行了研究,深入探究了n-damo菌的亚硝酸盐底物来源.结果显示,n-damo菌更多存在于旱地浅层土壤中,并且随季节变化分布在不同深度的土壤中.针对其pmo A基因的系统发育分析显示,旱地土壤中n-damo菌的群落结构具有明显的空间异质性,来自土壤0~20 cm和40~60 cm土层的序列完全分开,处于系统发育树不同分枝.针对其16S rRNA基因的实时荧光定量PCR结果显示,n-damo菌丰度随土壤深度的增加而降低,夏季丰度(1.44×10~4~1.02×10~5copies·g~(-1))低于冬季(3.66×104~2.67×105copies·g-1).在浅层土壤(0~20 cm)中,硝化反应和反硝化反应共同为n-damo菌提供亚硝酸盐底物来源;而在深层土壤(60~80 cm)中,亚硝酸盐底物主要来源于硝化反应.n-damo菌的活性(0.18 nmol·g~(-1)·d~(-1),以CO_2计)只能在夏季表层土壤(0~20 cm)中检测到,其余深度均未检测到其活性.在旱地农田土壤中,反硝化厌氧甲烷氧化菌对农田碳循环的影响可能不大.
The discovery of nitrite-dependent anaerobic methane-oxidizing (n-damo) oxidation of methane with nitrite as electron acceptor under anaerobic conditions has revolutionized the tradition of methane cycle It is understood that the community structure, abundance and activity of n-damo bacteria in upland farmlands (0-1 m) near the Beibeihe River in Hebei Province are studied by molecular biological methods and 13C and 15N stable isotope tracing techniques , In-depth exploration of n-damo bacteria nitrite substrate source.The results showed that, n-damo bacteria more in the shallow soil of dry land, and with the seasonal distribution in different depths of soil.For the pmo A gene The phylogenetic analysis showed that the community structure of n-damo in dryland soil had obvious spatial heterogeneity. The sequences from 0-20 cm soil layer and 40-60 cm soil layer in soil were completely separated and located in different branches of phylogenetic tree. The real-time PCR results of 16S rRNA gene showed that the abundance of n-damo decreased with the increase of soil depth, and the abundance of summer (1.44 × 10-4 ~ 1.02 × 10-5 copies · g -1) Lower than that in winter (3.66 × 104-2.67 × 105copies · g-1). In shallow soil (0-2 0 cm), nitrification and denitrification together provided the source of nitrite for n-damo bacteria, whereas in deep soil (60-80 cm), the nitrite substrate mainly came from the nitrification reaction.n- The activity of damo bacteria (0.18 nmol · g -1 · d -1, CO 2) was only detected in summer topsoil (0-20 cm), and no activity was detected in other depths In dry farmland soil, the effect of denitrifying anaerobic methane oxidizing bacteria on farmland carbon cycle may not be significant.