黄土高原草地土壤固碳微生物菌株特性及其固碳条件

CO2-fixing microbial strains in the grassland soil of the Loess Plateau: characteristics and CO2 fixation conditions

摘要:

目的 筛选并明确草地土壤固碳微生物菌株的生理生化特性及其最适固碳条件，为深入认识土壤固碳微生物的固碳机制、提升草地土壤碳汇能力提供理论依据。方法 采用无碳源固体培养基和稀释涂布法，从黄土高原草地土壤中分离筛选可培养的固碳微生物菌株，并借助16S rRNA基因鉴定物种。依据革兰氏染色、淀粉水解、吲哚、甲基红和乳酸发酵试验确定其生理生化特性。利用无碳源液体培养基及灭菌土壤的培养试验，确定温度(20-40 ℃)、水分(3.00%- 27.00%)，以及亚硝酸钠(NaNO₂)和硫化钠(Na₂S)电子供体的存在对固碳微生物固碳效率的影响。结果 共分离出9株固定CO₂效果良好的细菌，分属芽孢杆菌属、链霉菌属、剑菌属、农杆菌属、肠杆菌属、短波单胞菌属和噬脯氨酸菌属。其中，属于农杆菌属的A4和属于短波单胞菌属的A7固碳效率最高(P<0.05)，均为革兰氏阳性菌。这9株细菌在25-30 ℃，以及土壤水分3.00%、15.00%和27.00%的条件下，固碳效率较高(P<0.05)。添加电子供体可提升菌株固碳效率，提升效果依次为：单独添加NaNO₂>单独添加Na₂S>共同添加NaNO₂+Na₂S (P<0.05)。结论 本研究确定了优势固碳微生物菌株以及适宜固定CO₂的条件，为提升黄土高原陆地生态系统碳汇、减缓温室效应提供了理论依据和技术支持。

Abstract:

Objective To screen CO₂-fixing microbial strains in grassland soil, clarify their physiological and biochemical characteristics, and determine their optimal CO₂ fixation conditions, providing a theoretical basis for understanding the mechanisms of soil CO₂ fixation and enhancing grassland soil carbon sink.Methods The carbon-free solid medium and the dilution plating method were employed to isolate CO₂-fixing microbial strains from grassland soil in the Loess Plateau. The strains were identified via 16S rRNA gene sequencing. Physiological and biochemical characteristics of the strains were determined by Gram staining and starch hydrolysis, indole production, methyl red, and lactic acid fermentation tests. Culture experiments with carbon-free liquid medium and sterilized soil were carried out to assess the CO₂ fixation efficiency under varying temperatures (20-40 ℃), soil moisture levels (3.00%-27.00%), and the presence of electron donors (NaNO₂ and Na₂S).Results Nine bacterial strains with effective CO₂ fixation were isolated, belonging to Bacillus, Streptomyces, Sinorhizobium, Agrobacterium, Enterobacter, Brevundimonas, and Prolinoborus. Among them, strains A4 (Agrobacterium) and A7 (Brevundimonas) exhibited the highest CO₂ fixation efficiency (P<0.05), both being Gram-positive. Optimal conditions for CO₂ fixation of the nine strains were 25-30 ℃ and soil moisture of 3.00%, 15.00%, or 27.00% (P<0.05). Electron donor supplementation enhanced CO₂ fixation efficiency, and the enhancement effect followed the order: single addition of NaNO₂>single addition of Na₂S>co-addition of NaNO₂+Na₂S (P<0.05).Conclusion This study identified the dominant CO₂-fixing microbial strains and the conditions suitable for CO₂ fixation, providing a theoretical basis and technical support for enhancing the carbon sink of the terrestrial ecosystem on the Loess Plateau and mitigating the greenhouse effect.