李家河水库春季分层期nirS型反硝化菌群特征分析

Characteristic Analysis of nirS Denitrifying Bacterial Community in Lijiahe Reservoir During Stratification

为探究水源水库春季分层期(3~5月)nirS型反硝化细菌群落结构组成及其与水质的关系,以李家河水库为例,采用原位监测耦合Illumina高通量测序技术,分析了水体水质及反硝化细菌群落相对丰度及结构特征.结果表明:(1)通过高通量测序,鉴定为4门13属,优势菌门为变形菌门(Proteobacteria),相对丰度在52.5%~70.6%,时间尺度总体呈降低趋势(P<0.05),空间尺度上表层和中层高于底层(P<0.05),表层与中层无差异(P>0.05);识别出具有反硝化功能细菌8属,其中优势菌属(相对丰度>1%)为脱氯单胞菌属(Dechloromonas)和假单胞菌属(Pseudomonas),脱氯单胞菌属相对丰度在时间上呈先降低后升高的趋势,假单胞菌属在时间上呈先升高后降低的趋势,此2属在空间上无差异(P>0.05);细菌多样性及丰富度变化基本一致,时间上呈先升高后减低的趋势,空间上随深度逐渐升高;(2)本研究期间水库水体ρ(总氮)为2.35~2.91 mg·L^(-1),氮素污染较为严重,3月和4月垂向水体总氮基本一致且呈降低趋势,5月ρ(总氮)高于3月和4月且表层最高;(3)冗余分析(RDA)表明,主要驱动因素为水温、溶解氧、硝氮和氨氮,且氨氮与脱氯单胞菌属呈明显负相关.综上,通过对水源水库nirS型反硝化群落以及其影响因素的研究,有助于解析微污染水源水库反硝化细菌的群落变化特征,可对未来水源水体氮污染生物修复提供理论研究依据.

To explore the composition of the nirS denitrifying bacterial community during stratification in spring(March to May) in a drinking water reservoir and its relationship with water quality, the water quality and relative abundance and structure of the denitrifying bacterial community were analyzed using in-situ monitoring coupled with Illumina high-throughput sequencing technology in the Lijiahe Reservoir. The results showed that:(1) through high-throughput sequencing, 4 phyla and 13 genera were identified. The dominant bacterial phylum was Proteobacteria, and its relative abundance was between 52.5% and 70.6%. The overall trend of the relative abundance of Proteobacteria decreased on the time scale(P<0.05), and its relative abundance in the surface and middle layers was higher than that of the bottom layer on the spatial scale(P<0.05). There was no difference in the proportion of Proteobacteria between the surface and middle layers(P>0.05), and the abundance of its bottom layer was relatively stable;eight genera of bacteria with denitrification function were identified, among which the dominant bacterial genera(relative abundance>1%) were Dechloromonas and Pseudomonas. The relative abundance of Dechloromonas showed a trend of first decreasing and then increasing on the time scale, whereas the relative abundance of Pseudomonas showed a trend of increasing first and then decreasing on the time scale. There were no differences on the spatial scale between these two genera(P>0.05);the changes in bacterial diversity and abundance were basically similar, with a trend of first increasing and then decreasing on the time scale. The highest diversity and abundance of the bacterial community gradually increased with increasing depth on the spatial scale.(2) ρ(TN)of the reservoir during stratification was 2.35-2.91 mg·L^(-1), and the nitrogen pollution was more serious. In March and April, ρ(TN)on the vertical scale was basically similar and showed a decreasing trend. In May, the content of total nitrogen was higher than that in March and April, and the highest value of total nitrogen content occurred in the surface layer.(3) Redundancy analysis showed that water temperature, dissolved oxygen, nitrate, and ammonia nitrogen were the main driving factors, and ammonia nitrogen showed a significantly negative correlation with Dechlormonas. In summary, the study of nirS-type denitrification communities and related influencing factors will contribute to analyzing the characteristics of denitrifying bacterial community changes in a micro-polluted drinking water reservoir and provide a theoretical research basis for the biological remediation of nitrogen pollution in such reservoirs in the future.