CO2 Sequestration Potential and Soil Improvement Effects by Carbon-Fixing Bacteria Isolated From Degraded Soils in Shendong Coal Mining Area Located in Northwest China

Efficient carbon-sequestering microorganisms are crucial for enhancing soil quality and reducing carbon emissions, particularly in semiarid coal mining areas. In this study, we analyzed the soil carbon-fixing microbial taxa and pathways in the Shendong mining area via high-throughput sequencing, and concluded that their main carbon sequestering pathway is the reduced citrate cycle (rTCA cycle), which has the potential for microbial carbon sequestration. Bacterial strains with high CO₂ sequestration efficiency were isolated and identified, and their potential for improving soil carbon storage and quality was assessed. Through a systematic process of isolation, identification, and functional assessment, three dominant strains, Streptomyces marokkonensis FC1, Streptomyces viridochromogenes FC2, and Dyadobacter endophyticus FC3 with significant CO₂ sequestration capacity were obtained. Their adaptability and carbon fixation efficiency were confirmed through physiological, biochemical, and genetic analyses. The results from indoor ¹³C isotope labeling experiments and 42-day soil improvement experiments demonstrated that CO₂ sequestration and soil improvement effects were achieved in coal mine soils under semiarid conditions. Among the strains, FC2 presented the highest carbon fixation potential and soil improvement efficiency at approximately 8% soil water content. This highlights the potential application of carbon-fixing bacteria in microbial-based strategies for the ecological restoration of degraded mining soils.