免耕水稻土固定CO2自养微生物多样性

使用13CO2为标记物,采用稳定性同位素核酸探针(DNA-SIP)技术和微宇宙模拟的方法,对两种南方免耕水稻土中的固定CO2自养微生物群落结构和多样性进行了研究.实验结果表明,经80d的培养后,从13CO2标记处理的土样提取的DNA经氯化铯密度梯度离心后其浮力密度显著区分于12CO2对照组,表明土壤样品中的固定CO2自养微生物对CO2具有同化利用.RT-PCR结果表明两种标记土样DNA密度梯度离心分层的cbbLR基因的拷贝数最高分别为1.36×105拷贝/g干土和2.21×105拷贝/g干土.克隆文库分析和系统发育分析表明两种土壤中的固定CO2自养微生物群落结构具有一定差异.Bradyrhizobium和Rubrivivax是为FG土壤中的主要类群, 占全部克隆数的60.40%和13.86%.而TF土壤的主要类群是Rhodopseudomonas、Rhodospirillum、Methylibium和Variovorax,分别占全部克隆数的20.90%、11.94%、16.42%和10.45%.两种13CO2标记土样的cbbLR基因文库OTU类型、多样性指数均高于12CO2对照文库,其群落结构也有明显的变化.因此,免耕水稻土存在高度多样性的二氧化碳固定自养微生物,在农田土壤碳素循环方面具有重要作用.

Diversities of autotrophic CO2-fixing microbes in no-tillage paddy soils

The aim of the study was to investigate the diversity and community structure of autotrophic carbon dioxide-fixing bacteria by DNA-based stable isotope probing (DNA-SIP) technology and microcosm model method in no-till paddy soil in South China. The total DNAs by CsCl density-gradient centrifugation were separated on the basis of the buoyant density distinguishing after an 80-day incubation as templates, it showed that the carbon dioxide-fixing autotrophic microbes can assimilate and utilize carbon dioxide in soil. The RFLP-PCR showed that the highest copies of the cbbLR gene from two kinds of soil samples were 1.36×105 copies/g dry soil and 2.21×105 copies/g dry soil, respectively. The structure of carbon dioxide-fixing autotrophic microbial communities were significantly different from each other by clone library and phylogenesis analysis. Bradyrhizobium and Rubrivivax were the main microorganisms in soil FG and accounted for 60.40% and 13.86% of all clones, respectively. The community composition of carbon dioxide-fixing bacteria in soil TF was relatively uniform, and Rhodopseudomonas, Bradyrhizobium, Methylibium and Variovorax accounted for 20.92%, 11.94%, 16.42% and 10.45% of the total clones, respectively. The number of OTUs and diversity index of 13C-carbon dioxide stable isotope labeled cbbLR library were higher than these of the 12C-carbon dioxide labelled control library, and the community structure also showed significant differences. Together, we conclude that there are diverse autotrophic bacteria capable of fixing carbon dioxide in the no-tillage paddy soil, and they have an important role in the carbon cycling for farmland soils.