Bacterial communities are crucial for the functioning of wetlands as they play a critical role in energy flows and nutrient transformation.Poyang Lake,the largest freshwater lake in China,forms a large area of wetland due to its great changes in seasonal water levels,which play an important ecological role in the middle and lower reaches of Yangtze River.In this study,surface soils (0-10 cm) covered with typical plants were sampled at five sites from the lake surface to a sloping field in Poyang Lake wetland in November 2014.Chemical parameters measured in the soil included NH4+-N,NO3--N,TN,TP,and SOC.We profiled the bacterial community structure by sequencing the V3-V4 16S rRNA gene on the Illumina Miseq PE300,using 338F (5'-ACTCCTACGGGAGGCAGCA-3') and 806R (5'-GGACTACHVGGGTWTCTAAT-3') primers.A total of 134,223 bacterial sequences were obtained,and a similarity of 97％ was used to identify operational taxonomic units (OTUs),which resulted in a total of 2,072.The phylogenetic affiliation of each 16S rRNA gene sequence was analyzed by an RDP Classifier against the Silva 16S rRNA database.The coverage of all soils was over 99％,indicating a deep sequencing.The bacterial community richness calculated by the Chao1 estimator and the bacterial community diversity calculated by the Shannon index showed the same trend among the five soils covered with different plants:Carex soil ＞ Carex-Phalaris soil ＞ Phragmites soil ＞ mud flat soil ＞ Artemisia soil.The principal component analysis of OTUs showed that the bacterial community structure was more similar among soils that were closer along the transition from the lake surface to the sloping field.The bacterial community structure was similar among Carex-Phalaris soil,Carex soil,and Phragmites soil,but very different between mud flat soil and Artemisia soil.Proteobacteria (30.0％ of total sequences) was the most abundant phylum in Poyang Lake wetland,mainly including Alphaproteobacteria (7.2％),Betaproteobacteria (8.9％),Deltaproteobacteria (10.5％),and Gammaproteobacteria (2.8％).Except for Proteobacteria,other phyla with high abundance were Acidobacteria (16.7％),Chloroflexi (16.5％),Nitrospirae (10.2％),Firmicutes (7.5％),Actinobacteria (4.8％),Gemmatimonadetes (3.8％),and Chlorobi (1.8％).Proteobacteria was the most abundant phylum in Carex,Carex-Phalaris,and Phragmites soils,and the third most abundant phylum in mud flat and Artemisia soils,after Chloroflexi and Nitrospirae (first abundant phylum in mud flat and Artemisia soils,respectively),and Acidobacteria and Chloroflexi (second abundant phylum in mud flat and Artemisia soils,respectively).Most of the phyla's relative abundance had an obvious trend along the transition from the lake surface to the sloping field.Nitrospira (10.2％) was the most abundant genus in this area,and the Nitrospirae abundance was much higher than that in other wetland soils,reflecting the importance of the nitrogen cycle in the ecological system of Poyang Lake wetland.There were many norank or uncultured genera,making it difficult to study their ecological functions.Redundancy analysis of bacterial phyla and chemical parameters in soil showed that TP,NH~-N,and SOC had more relevance to the bacterial community structure.The results of this study showed that there were differences in bacterial community structure among soils covered with different plants in the Poyang Lake wetland,and these differences had regular variation along the transition from the lake surface to the sloping field.%采用高通量测序技术分析了鄱阳湖典型湿地土壤细菌群落特征.测序结果表明,不同植被土壤细菌群落丰度与多样性的排序相同:苔草带＞苔草-虉草带＞芦苇带＞泥滩带＞藜蒿带.沿湖面至坡地,空间位置相近的土壤细菌群落结构具有更大的相似性,苔草-虉草带、苔草带和芦苇带的细菌群落结构相近,泥滩带和藜蒿带的细菌群落结构差异较大.变形菌门(30.0％)是湿地土壤平均相对丰度最高的门,其次为酸杆菌门(16.7％)和绿弯菌门(16.5％);多数门分类细菌相对丰度沿湖面至坡地存在一定变化趋势.硝化螺菌属是第一大属分类水平细菌群落.在土壤化学指标中,与鄱阳湖湿地细菌群落相关性较大的是总磷、铵态氮和有机质含量.以上研究结果表明,鄱阳湖湿地不同植被土壤细菌群落具有结构性差异,但沿湖面至坡地存在规律性变化.
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