基于宏基因组学揭示咸水滴灌对棉田土壤微生物的影响

Revealing the Effect of Saline Water Drip Irrigation on Soil Microorganisms in Cotton Fields Based on Metagenomics

咸水灌溉已成为缓解干旱区淡水短缺的重要手段,但长期咸水灌溉会造成土壤盐分积累,影响土壤微生物群落结构,进而影响土壤养分转化.通过宏基因组学的手段探究长期咸水滴灌对棉田土壤微生物群落结构的影响,试验中灌溉水盐度(ECw)设2个处理:0.35 dS·m^(-1)和8.04 dS·m^(-1)(分别用FW和SW表示),施氮量分别为0 kg·hm^(-2)和360 kg·hm^(-2)(分别用N0和N360表示).结果表明,咸水灌溉提高土壤含水量、盐分、有机碳和全氮含量,降低土壤pH和速效钾含量,氮肥施用增加土壤有机碳、盐分和全氮含量,降低土壤含水量、 pH和速效钾含量.各处理土壤的优势菌门为:变形菌门、放线菌门、酸杆菌门、绿弯菌门和芽单胞菌门.咸水灌溉显著提高放线菌门、绿弯菌门、芽单胞菌门和厚壁菌门的相对丰度,显著降低变形菌门、酸杆菌门、蓝细菌和硝化螺旋菌门的相对丰度.氮肥施用显著提高绿弯菌门和硝化螺旋菌门的相对丰度,显著降低酸杆菌门、芽单胞菌门、浮霉菌门、蓝细菌和疣微菌门的相对丰度.LEfSe分析表明,咸水灌溉对土壤微生物群落潜在生物的标志物数量无明显影响,氮肥施用降低土壤微生物群落潜在生物的标志物数量.相关性网络图表明,20个菌属间相关性程度不同,其中有44个正相关关系和48个负相关关系,网络图中核心物种为类诺卡式菌属、Streptomyces、Pyrinomonas、Candidatus_Solibacter和慢生根瘤菌属.咸水灌溉提高反硝化基因nirK、nirS、nasB和norC的相对丰度,降低硝化基因amoB、amoC和nxrA的相对丰度,氮肥施用提高硝化基因amoA、amoB、amoC、hao和nxrA的相对丰度,降低反硝化基因narB、napA、nasA和nosZ的相对丰度.咸水灌溉会对土壤理化性质产生不利影响,SWC、 EC_(1∶5)和BD是影响土壤微生物群落结构和功能基因的主要驱动因子,土壤微生物通过调节物种组成来适应土壤盐胁迫.

Saline water irrigation has become an important means to alleviate the shortage of freshwater in arid areas.However,long-term saline water irrigation can cause soil salinity accumulation,affect soil microbial community structure,and then affect soil nutrient transformation.In this study,we used metagenomics to investigate the effects of long-term saline water drip irrigation on soil microbial community structure in a cotton field.In the experiment,the salinity of irrigation water(ECw) was set to two treatments:0.35 dS·m^(-1) and 8.04 dS·m^(-1)(denoted as FW and SW,respectively),and the nitrogen application rates were 0 kg·hm^(-2)and 360 kg·hm^(-2)(denoted as N0 and N360,respectively).The results showed that saline water irrigation increased soil water content,salinity,organic carbon,and total nitrogen content and decreased soil pH and available potassium content.Nitrogen fertilizer application increased soil organic carbon,salinity,and total nitrogen content and decreased soil water content,pH,and available potassium content.The dominant bacterial phyla in each treatment were:Proteobacteria,Actinobacteria,Acidobacteria,Chloroflexi,and Gemmatimonadetes.Saline water irrigation significantly increased the relative abundances of Actinobacteria,Chloroflexi,Gemmatimonadetes,and Firmicutes but significantly decreased the relative abundances of Proteobacteria,Acidobacteria,Cyanobacteria,and Nitrospira.Nitrogen fertilizer application significantly increased the relative abundances of Chloroflexi and Nitrospira but significantly decreased the relative abundances of Acidobacteria,Gemmatimonadetes,Planctomycetes,Cyanobacteria,and Verrucomicrobia.LEfSe analysis showed that saline water irrigation had no significant effect on the number of potential biomarkers,and nitrogen fertilizer application decreased the number of potential biomarkers in soil microbial communities.The correlation network diagram showed that the 20 genera had different degrees of correlation,including 44 positive correlations and 48 negative correlations.The core species in the network diagram were Nocardioides,Streptomyces,Pyrinomonas,Candidatus_Solibacter,and Bradyrhizobium spp.Saline water irrigation increased the relative abundances of the denitrification genes nirK,nirS,nasB,and norC and decreased the relative abundances of the nitrification genes amoB,amoC,and nxrA,whereas nitrogen fertilizer application increased the relative abundances of the nitrification genes amoA,amoB,amoC,hao,and nxrA and decreased the relative abundances of the denitrifying genes narB,napA,nasA,and nosZ.Saline water irrigation could adversely affect soil physicochemical properties;SWC,EC_(1∶5),and BD were the main driving factors affecting soil microbial community structure and function genes;and soil microorganisms adapted to soil salt stress by regulating species composition.