稻虾共作模式下稻田土壤氨氧化微生物丰度和群落结构的特征

Characteristics of ammonia oxidation microbial abundance and community structure in paddy soils of rice–crayfish symbiosis farming system

【目的】研究稻虾共作模式下土壤氨氧化微生物数量、群落多样性及群落结构,深入了解该模式下的土壤微生态环境的演变。【方法】试验点在湖北省荆州市长江大学农学院基地,设置稻虾共作模式(CR)与常规中稻种植模式(MR),借助荧光定量PCR技术与Illumina Miseq高通量测序平台,分析了土壤氨氧化细菌(AOB)与古菌(AOA)丰度、多样性及群落结构。【结果】与MR模式相比,CR模式显著提高了土壤硝态氮、总碳及总氮含量,对土壤p H、碱解氮及土壤碳氮比无显著影响。CR模式土壤AOA与AOB amo A基因拷贝数为3.13×10^5和7.01×10^5 copies/g干土,MR模式土壤AOA、AOB amoA基因拷贝数为1.41×10^5和3.87×10^5 copies/g干土,两个模式土壤AOB的数量均显著高于AOA,CR模式土壤AOA、AOB的数量均显著高于MR模式(P<0.05)。α群落多样性指数表明,相比MR,CR模式显著降低了土壤AOA群落多样性,对AOB群落多样性无显著影响。Venn结果分析,CR模式增加了AOA amoA基因的物种,改变了AOB amoA基因的物种组成,且AOB amoA物种数量下降。在属水平上,norank_c_environmental_samples_p_Thaumarchaeota、unclassified_k_norank_d_Archaea、norank_c_environmental_samples_p_Crenarchaeota、norank_p_environmental_samples_k_norank为AOA的优势类群,相对丰度占AOA amoA基因总序列的99.25%~99.46%,CR模式显著提高了norank_c_environmental_samples_p_Crenarchaeota在AOA群落属水平的相对丰度;unclassified_k_norank_d_Bacteria、norank_f_environmental_samples、norank_o_environmental_samples_c_Betaproteobacteria、unclassified_o_Nitrosomonadales为AOB的优势类群,相对丰度共占97.78%~98.49%,且CR模式显著增加了norank_o_environmental_samples_c_Betaproteobacteria与unclassified_o_Nitrosomonadales在AOB群落属水平的相对丰度。冗余分析(RDA)结果显示,土壤基本理化性质对于土壤AOA、AOB群落结构影响有着相似的趋势,其中对AOA、AOB群落结构影响最大的因子是硝态氮,其次分别为总碳、铵态氮、碱解氮、pH。根据RDA投影距离分析,稻虾共作模式对土壤AOA群落结构的影响大于AOB,且MR与稻虾共作模式土壤AOB的群落结构具有一定的相似度。【结论】稻虾共作模式显著降低了AOA群落多样性,而对AOB群落无显著影响;稻虾共作模式显著增加了AOA与AOB的丰度并显著影响了群落结构组成。土壤硝态氮、总碳、铵态氮、碱解氮、pH含量是导致土壤微生物数量、多样性及群落结构变化的主要原因。

【Objectives】To study the abundance and community structure of ammonia-oxidizing microbes in paddy soil under rice-crayfish farming system,for deeper understanding the changing trend of the microbial ecosystem under the system.【Methods】The study was carried out at the Base of Agricultural College,Yangtze University in Jingzhou,Hubei Province.The comparison of conventional mid-season rice planting model(MR),and rice-crayfish symbiosis farming system(CR)was conducted using the technology of real-time fluorescence quantitative PCR and the platform of Illumina Miseq high-throughput sequencing to study the impact of ricecrayfish farming system on the abundance,diversity and community structure of ammonia oxidation microbes in different soils.【Results】Rice-crayfish farming system significantly increased the content of soil nitrate,total carbon and total nitrogen.However,the effects on soil pH,alkali-hydrolyzable nitrogen,carbon and nitrogen ratio in soil were insignificant.The copy number of AOA amoA gene and AOB amoA gene was 3.13×10^5 and 7.01×10^5/g dry soil)respectively under CR system,while the copy number of AOA amoA gene and AOB amoA gene was 1.41×10^5 and 3.87×10^5/g dry soil,respectively under MR system.The number of soil AOA and AOB was significantly higher in CR system,and the number of AOB was significantly higher than that of AOA in both CR and MR system.Theαcommunity diversity index indicated that CR system significantly decreased the community diversity of soil AOA but did not significantly affect the community diversity of soil AOB.Analysis of Venn results showed that CR system increased the number of species of AOA amoA gene and changed the species composition of AOB amoA gene,accompanied by the decrease in the number of species AOB amoA.At the generic level,norank_c_environmental_samples_p_Thaumarchaeota,unclassified_k_norank_d_Archaea,norank_c_environmental_samples_p_Crenarchaeota,norank_p_environmental_samples_k_norank were the predominant phyla of AOA,and their relative abundance accounted to 99.25%–99.46%of AOA total sequence of amoA gene.Moreover,CR significantly increased relative value of abundance of norank_c_environmental_samples_p_Crenarchaeota at the AOA genus level.unclassified_k_norank_d_Bacteria,norank_f_environmental_samples,norank_o_environmental_samples_c_Betaproteobacteria,unclassified_o_Nitrosomonadales were the main genus group of AOB,and their relative abundance was 97.78%–98.49%.The CR system significantly increased the relative abundance of norank_o_environmental_samples_c_Betaproteobacteria and unclassified_o_Nitrosomonadales at the AOB gene level.Redundancy analysis(RDA)showed that the community structure of soil AOA and AOB was similarly affected by the physical and chemical properties of soil.The most influential factor for community structure of soil AOA and AOB was nitrate nitrogen,followed by total carbon and ammonium nitrogen,alkali-hydrolyzable nitrogen,and pH.Based on the analysis of distance of RDA projecting,the effect of CR system on soil AOA community structure was greater than that of AOB,and MR was similar to CR in terms of the system to the community structure of soil AOB.【Conclusions】Rice-crayfish symbiosis farming system has significantly decreased the diversity of AOA communities,but does not significantly affect AOB communities.Rice-crayfish symbiosis farming system also significantly increases the abundance of AOA and AOB and significantly affects the structure of the community.Soil nitrate nitrogen,total carbon,ammonium nitrogen,alkali-hydrolyzable nitrogen and pH affect soil microbial quantity and diversity,which are the main reasons for community structure changes.