土壤微生物分解含硫氨基酸规律及其化学计量学调控机制

半胱氨酸和蛋氨酸是一类既含氮又含硫的特殊氨基酸，可为微生物和植物提供氮源和硫源，然而其中碳、氮和硫在时间尺度上的循环利用及其微生物机制还未可知。我们拟采用洛桑试验站长期点位点土壤，采用13C、15N、14C和35S放射性同位素结合稳定性同位素同步标记技术，研究土壤微生物吸收利用氨基酸机理。采用13C-PLFA、13C-DNA-SIP技术，研究哪些微生物在竞争吸收氨基酸中起到核心作用；并且采用UHPLC-QTOFMS/MS检测微生物中13C标记的有机分子，进而推测微生物利用氨基酸的分子途径，分析微生物吸收利用半胱氨酸和蛋氨酸后如何维持自身化学计量学平衡。最后，研究氨基酸在土壤溶液中的分解，确定土壤溶液少量的微生物能否将土壤中半胱氨酸和蛋氨酸迅速分解，并且探索长期施肥是否会影响氨基酸分解过程。该研究对深入理解土壤元素循环微生物分子机制具有重要的理论价值，对植物硫营养具有重要的应用价值。

Cysteine and methionine are a kind of special amino acids containing both nitrogen and sulfur, which can provide nitrogen and sulfur sources for microorganisms and plants. However, the recycling and utilization of carbon, nitrogen and sulfur in amino acids on the time scale and their microbial mechanisms are unknown. We plan to study the mechanism of soil microbial absorption and utilization of cysteine and methionine by using 13C, 15N, 14C and 35S, combination radioisotopes with stable isotope labeling technique under the long-term fertilization soil. 13C-PLFA and 13C-DNA-SIP techniques will be used to study which microorganisms played a key role in the competitive absorption of amino acids. In addition, UHPLC-QTOFMS/MS will be used to detect 13C-labeled organic molecules in microorganisms, so as to predict the molecular pathways of microbial utilization of cysteine and methionine, and analyze how microorganisms maintain their stoichiometric balance after absorption and utilization of cysteine and methionine. Finally, the decomposition of amino acids in soil solution was studied to determine whether small amount of microorganisms in soil solution could rapidly decompose cysteine and methionine, and to explore whether long-term fertilization would affect the decomposition process of amino acids. This study has important theoretical value for further understanding the molecular mechanism of soil element cycling microorganisms, and has important application value for efficient utilization of plant sulfur.