稻田土壤固碳功能微生物群落结构和数量特征

研究不同类型稻田土壤自养微生物数量和多样性差异及其影响因子,对全面认识稻田生态系统的固碳潜力及其机制具有重要意义.鉴于此,本文选取4种典型稻田土壤,通过室内培养实验对具备卡尔文循环途径碳同化微生物进行了研究.利用荧光定量PCR(qPCR)、克隆文库以及末端限制性长度多态性分析(T-RFLP)技术,研究了卡尔文循环关键酶(1,5二磷酸核酮糖羧化酶/加氧酶Rubis CO)的2种编码基因(cbbL和cbbM)的丰度和多样性.结果表明,与培养前相比,培养45 d后碳同化自养微生物数量有所增加,cbbL基因丰度比cbbM基因高3个数量级.不同稻田土壤中碳同化功能微生物优势种群存在差异,且这些微生物大多不能归类到已知的细菌类群中,部分可归类的与变形菌和放线菌有较高相似度.RDA分析结果显示土壤有机碳(SOC)、阳离子交换量(CEC)、pH、黏粒、粉粒和砂粒含量对碳同化功能微生物群落结构有显著影响.本文的研究结果对于理解微生物在碳循环过程中的作用具有一定的科学意义,也可以为稻田土壤肥力科学化管理和构建低碳农业提供科学依据.

Characteristic of Abundances and Diversity of Carbon Dioxide Fixation Microbes in Paddy Soils

To get a better understanding of the microbial autotrophic carbon sequestration potential of paddy fields and its mechanisms, soil incubation experiment was conducted for four representative paddy soils. The molecular biological methodsquantitative PCR (qPCR), clone library and terminal-restriction fragment length polymorphism (T-RFLP) technique] based on cbbL and cbbM genes encoding the key enzymesribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO)] of Calvin cycle were used to determine the abundance and diversity of autotrophic microbes. The results showed that, after 45 days of incubation, carbon dioxide fixation autotrophic microbial abundances were generally increased compared with those before incubation, and cbbL gene abundances were approximately three magnitudes higher than those of cbbM. Dominant microbial populations varied among the four paddy soils, and most of these OTUs were distantly related to known sequences, only part of them could be grouped into Proteobacteria and Actinobacteria. RDA analysis results showed that soil organic carbon (SOC), cation exchange capacity (CEC), pH, clay, silk and sand content had significant effects on the CO₂ fixation microbial community. Consequently, the results of this study provide significant reference to understand the role of microorganisms in carbon cycle process. The results are helpful for providing a scientific basis for scientific management of paddy soil fertility and low carbon agriculture construction.