应用气-质联机和同位素双标记技术对土壤微生物吸收有机氮的研究

摘要

The direct absorption and utilization of low-molecular weight organic nitrogen (N)by soil microbial is a new subj ect in the research of microbial N nutrition.The study used gas chromatography-mass spectrometry to trace dual-labeled (13 C,15 N) glycine from the soil solution and microorganisms.The results showed that glycine added to the soil was quickly taken up by soil microorganisms,with the half-life of glycine being 2.9 h.Withthe incubation of 4 h,the maximum amount of dual-labeled gly-cine in the microbial biomass was measured (equivalent to 10% of glycine added),indicating that added glycine was absorbed as intact molecular by soil microorganisms.The single labeled-Keto acid was detected in soil solution and in the microorganisms (decomposed production by double labeled glycine),but the content is extremely low,suggesting that added glycine mainly served as carbon (C)source for soil microbial life activities.This study demonstrated that compound specific stable dual labeled isotope analysis combined with chloroform fumigation technique was an effective method for detecting the low-molecular organic N utilized by soil microorganisms.%土壤微生物对小分子有机氮的直接吸收和利用是目前微生物氮素营养研究的新方向。本研究通过气相色谱-质谱(GC-MS)对双标记氨基酸(13 C,15 N)的测定技术探讨土壤微生物对有机氮分子的直接吸收和利用。结果表明：加入土壤中的甘氨酸被微生物迅速利用,半衰期为2.9 h。培养4 h后在微生物体内检测到最大量的双标记甘氨酸(相当于甘氨酸加入量的10%),说明甘氨酸可以被微生物以完整分子形式所吸收。通过此手段也可检测到土壤溶液和微生物体内的单标记 a-酮酸(双标记甘氨酸分解后的产物),但含量极少,说明加入的甘氨酸主要向微生物提供C源供其生命活动。本研究证明专性化合物同位素双标记手段结合氯仿熏蒸技术是检测微生物吸收小分子有机氮的有效手段。