宁夏枸杞种植地土壤中微生物分布调查及降解农残研究

Study on the distribution of soil microorganisms and degradation of pesticide residue in Ningxia Lycium field

为了考察枸杞种植地土壤中微生物(细菌、霉菌、放线菌)的分布情况,筛选优势菌株,并考察其降解农药残留的能力。通过稀释涂布法对宁夏5个枸杞种植区(H区、N区、K区、Z区、B区)3个不同深度土壤样品进行细菌、霉菌、放线菌的种类及数量研究,利用16S rDNA鉴定微生物,利用液质联用仪检测农残质量浓度。结果表明,5个区域3种主要微生物分布规律各不相同,其中N区细菌及霉菌数量最多,K区放线菌数量最多。N区、Z区的3种微生物数量随采样深度增加而呈减少趋势,K区则相反。H区与B区的细菌数量随采样深度增加而减少,霉菌分布规律均随深度增加表现为先减少后增加的趋势,两区放线菌分布趋势则相反。筛选出的优势菌株在低浓度农药中降解的效率较高,如氧化乐果、对硫磷,其降解率可达100%,其余农药的降解率在30%~80%。在高浓度农药培养基中,菌株对氧化乐果、对硫磷的降解率下降至60%~80%,其余4种农药降解率下降至28%~51%。研究表明,不同种植区域土壤中3种主要微生物的分布规律与污染物种类及土壤中元素种类有一定的关系,分离出的优势菌中细菌的数量及种类最多且多为芽孢杆菌属。筛选出的3种优势菌株对农残有一定的降解能力。

This study investigates soil microorganism community distribution in Ningxia Lycium fields.Dominant strains were screened out,and their ability on pesticide residue degradation was evaluated.Soils from 5 wolfberry growing regions(H、N、K、Z、B)in Ningxia were collected in different depths.An analysis of three kinds of microorganism(bacteria、actinomycetes and mold)were conducted using the dilution coating method.In this study,16S rDNA was used for the identification of microorganisms,and liquid chromatography-tandem mass spectrometry was used for the determination of pesticide residues.The obtained results demonstrated that the distribution patterns of the three kinds of microorganisms among five regions varied differently,among which the number of bacteria and mold in zone N was the largest,and the number of actinomycetes in zone K was the largest.It was observed that the number of bacteria,mold,and actinomycetes in zone N and zone Z decreased with an increase of sampling depth,in contrast to that in zone K.Also,the number of bacteria in zone H and zone B is negatively correlated with the sampling depth,while the number of actinomycetes was the opposite.The number of mold in zone H and zone B decreased firstly and then increased.The selected dominant strains were revealed to degrade low-concentration pesticide residue in soil efficiently,and its degradation rate of omethoate and parathion was up to 100%,and the degradation rate of other pesticides was between 30%and 80%.When strains were exposed to a high-concentration pesticide medium,the degradation rate of omethoate and parathion dropped to 60%—80%,and the degradation rate of the remaining four pesticides dropped to 28%~51%.Studies have shown that the distribution of the three kinds of microorganisms among different planting regions was significantly affected by pollutants and elements present in the soil.The separated dominant strains were almost Bacillus,and three dominant strains screened out had great degradation capacity to pesticide residues.