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微生物生长对底物的可利用性存在不同的响应,外源氮素的形态可以显著影响微生物代谢过程,而土壤氨基糖作为微生物细胞壁残留物,其形成、分解和周转特征与外源碳氮供给密切相关,对土壤氨基糖的研究与同位素标记技术相结合,可以进一步反映微生物对底物的利用特征.本文以葡萄糖及15N标记的NH4+和NO3-为底物,利用气相色谱-质谱联机技术,通过测定氨基糖中同位素富集比例,跟踪新形成(标记)和原有(非标记)的土壤氨基糖的动态变化.结果表明:在培养过程中,15N标记的氨基糖含量显著增加,NH4+向氨基糖的转化显著高于NO3-,反映出微生物对NH4+的选择性利用.土壤中原有的氨基糖也发生了不同变化.其中,非标记氨基葡萄糖在NH4+为底物时,其含量有所增加,但在NO3-为底物时含量逐渐下降;非标记胞壁酸含量在2个处理中均不断下降,尤其以NO3-为底物时更为显著;非标记氨基半乳糖含量的增减幅度均小于20%.这种特异性变化表明,不同来源的微生物细胞壁残留物对土壤氮素周转和稳定的作用不同,真菌细胞壁残留物易于在土壤中积累,有利于土壤有机质的稳定,而细菌细胞壁残留物容易分解,在土壤有机质周转过程中起重要作用.
Microbial growth has different responses to the availability of substrate. The morphology of exogenous nitrogen can significantly affect the microbial metabolic process. However, the formation, decomposition and turnover characteristics of soil amino sugar as microbial cell wall residues are related to the supply of exogenous carbon and nitrogen Closely related to the study of soil amino sugar and isotope labeling technology can further reflect the use of microorganisms on the substrate characteristics.In this paper, glucose and 15N labeled NH4 + and NO3- as substrate, the use of gas chromatography-mass spectrometry online technology, The dynamic changes of amino sugar in newly formed (labeled) and original (non-labeled) soil were followed by measuring the ratio of isotope enrichment in amino sugar.The results showed that the content of 15N-labeled aminosugar significantly increased while NH4 + The conversion of amino sugars was significantly higher than that of NO3-, reflecting the selective utilization of NH4 + by microorganisms. The original amino sugars in soil also changed differently, of which the content of non-labeled glucosamine increased when NH4 + was the substrate , But the content of NO3- decreased gradually. The content of non-labeled muramic acid decreased continuously in both treatments, especially when NO3- was the substrate. The non-labeled The changes of galactosyl content were all less than 20% .These specific changes indicated that microbial cell wall residues of different origins had different effects on soil nitrogen turnover and stability, and fungal cell wall residues were easy to accumulate in the soil, which was in favor of The stability of soil organic matter, while the bacterial cell wall residue easily decomposed, plays an important role in soil organic matter turnover process.