太湖微生物群落演替对沉水植物残体降解的响应

Response of microbial community succession to degradation of submerged plant residues in Taihu Lake

摘要:

浅水湖泊沉积物中的有机质降解是调控碳循环与温室气体排放的关键过程，但沉水植物残体降解过程对微生物群落长期演替的调控机制尚未明晰。目的 探究在长时间尺度下沉水植物残体降解对微生物群落的驱动机制。方法 通过4年的微宇宙模拟实验，研究太湖沉积物中竹叶眼子菜(Potamogeton wrightii)残体降解的动态过程，详细解析了有机质组分演变、胞外酶活性对微生物群落演替的动态影响。结果 易降解有机质组分(labile organic matter pool, LP)的快速消耗伴随β-葡萄糖苷酶活性激增，而难降解有机质组分(recalcitrant organic matter pool, RP)累积与酚氧化酶活性滞后响应耦合。微生物群落呈现显著功能分异，芽孢杆菌门(Bacillota)和担子菌门(Basidiomycota)分别主导细菌与真菌群落难降解有机质的降解，揭示了木质素类聚合物降解的代谢分工。方差分解表明易降解有机质与难降解有机质都能独立解释微生物群落差异性，凸显有机质的化学复杂度对功能类群的筛选作用。结论 沉水植物残体降解显著驱动了微宇宙培养体系的微生物群落结构演替，微生物群落组成与有机质组分呈现出协同变化的趋势，并促进了具有不同生长策略的微生物生长。本研究阐明了沉水植物残体降解过程中微生物功能差异与有机质组分复杂度的动态互作规律，为浅水湖泊碳稳定性评估及生态修复提供了理论依据。

关键词:浅水湖泊;沉积物;沉水植物残体;有机质降解;微生物

Abstract:

Organic matter degradation in shallow lake sediments is a key process in regulating the carbon cycle and greenhouse gas emissions, while the mechanism by which submerged plant residue degradation regulates the long-term succession of microbial communities has not yet been clarified.Objective To investigate the mechanisms of microbial community succession driven by submerged plant residue degradation on long time scales.Methods We investigated the degradation dynamics of Potamogeton wrightii residues in Taihu Lake sediments through a 4-year microcosmic simulation experiment and analyzed in detail the dynamic impacts of organic matter fraction evolution and extracellular enzyme activities on microbial community succession.Results The rapid consumption of labile organic matter pool was accompanied by a surge in β- glucosidase activity, while the accumulation of recalcitrant organic matter pool was coupled with a lagged response of phenol oxidase activity. Microbial communities showed significant functional differentiation, with Bacillota and Basidiomycota dominating the degradation of recalcitrant organic matter pool in bacterial and fungal communities, respectively, revealing the metabolic division of labor in the degradation of lignin-like polymers. Variance decomposition showed that both labile and recalcitrant organic matter pools independently explained microbial community variations, highlighting the role of chemical complexity of organic matter in screening functional taxa.Conclusion Degradation of submerged plant residues significantly drove microbial community structure succession in the microcosmic culture system, and microbial community composition and organic matter fractions showed synergistic changes. In addition, the degradation promoted the growth of microorganisms with different growth strategies. This study elucidates the dynamic interactions between microbial functional differences and organic matter pool complexity in the degradation of submerged plant residues, providing a theoretical basis for carbon stability assessment and ecological restoration of shallow lakes.

Key words:shallow lakes;sediments;submerged plant residue;organic matter degradation;microorganisms