湖泊沉积物中微生物群落对天然有机质输入的响应

全球气候变化和蓝藻水华暴发造成湖泊生源、陆源天然有机质（NOM）输入显著增加，以太湖藻型湖湾为例，考察沉积物中微生物群落的活性、组成及功能对不同浓度藻源有机质（POM）和陆源腐殖酸（HA）的响应特征.三维荧光分析显示POM化学多样性较高，包含易降解的类蛋白（50%）和难降解的类腐殖质组分（50%），而类腐殖质占HA荧光组分的97%.两个月的微宇宙实验表明，对于同种NOM，沉积物中微生物矿化作用随NOM浓度升高而增强；但POM组中有机碳去除量显著高于同等浓度的HA组.胞外聚合物分析显示NOM输入有利于微生物分泌蛋白质和多糖，提高了微生物群落的聚集度和稳定性；酶活分析表明POM对脲酶、脱氢酶等有机物代谢酶的激发效应强于HA，形成了代谢更活跃的微生物群落.同时，NOM输入（尤其是POM）提高了微生物群落的物种多样性，增加了Proteobacteria和Bacteroidetes等参与有机物分解的菌群丰度，上调了与代谢相关的KEGG功能基因丰度.以上结果表明湖泊沉积物中微生物群落的活性和功能与NOM的来源和浓度有关.

Response of Microbial Community to Natural Organic Matter Input in Lake Sediments

Increased loads of biogenic and terrestrial natural organic matter into freshwater lakes are projected to be a major consequence of global climate change and cyanobacterial blooms. In this study, the effects of phytoplankton-derived organic matter (POM) and terrestrial humic acid (HA) on the activity, composition, and function of the microbial community in Lake Taihu sediments were investigated. Fluorescent spectra demonstrated that POM with high chemodiversity was composed of labile protein-like components (50%) and recalcitrant humic-like components (50%), while humic-like substances accounted for 97% of HA. Over two-month periods, the organic carbon mineralization in sediments was enhanced owing to increasing NOM concentrations; however, the carbon consumption in POM-amended sediments was significantly higher than that in sediments amended with the same concentrations of HA. Analysis of extracellular polymeric substances indicated that NOM input improved the microbial secretion of proteins and polysaccharides, increasing the aggregation and stability of the microbial community. The amendment of POM also stimulated the activity of organic matter metabolic enzymes, promoting microbial activity. Moreover, 16S rRNA gene sequencing suggested that the mineralization of NOM (especially POM) increased the diversity of the microbial community, favored the survival of Proteobacteria and Bacteroidetes, and upregulated the function genes of organic matter metabolism. These results suggest that the composition and function of microbial community in sediments were associated with the origin, composition, and concentration of NOM input.