微生物群落对氨胁迫响应的宏基因组学研究

为探析厌氧消化微生物群落对氨胁迫的响应，在串联批次实验中引入氨氮（TAN）胁迫，结合宏基因组学分析，研究了不同TAN浓度下，厌氧消化系统的过程参数、群落结构/组成及其功能基因/代谢途径的响应.结果显示，TAN为3000mg/L时，系统性能逐步优化；TAN为6000mg/L时，甲烷产率逐步下降，并伴随着丙酸、丁酸积累.从群落组成上看，两个氨氮梯度下，抗性和冗余性保障了水解酸化菌代谢底物的能力.产氢产乙酸和产甲烷方面，低氨氮组两类功能菌群丰度持续增加，但高氨氮组增加幅度低甚至出现丰度下降，指示该环节可能受到了氨胁迫.进一步分析两阶段的功能基因变化，发现产甲烷和互营乙酸氧化途径在氨胁迫下表现出抗性和冗余性，但高浓度TAN （6000mg/L）抑制了丁酸和丙酸代谢途径中关键基因ACADS和PCCA的表达.可见，氨抑制失稳的关键环节是产氢产乙酸阶段.

Metagenomic analysis on the responses of microbial community to ammonia stress

A series of batch experiments were conducted to investigate the responses of anaerobic digestion (AD) microbial community exposed to ammonia (TAN) stress. In combination with Metagenomic sequencing analysis, this paper investigated the responses of process parameters, community structure/composition and functional gene/metabolic pathways of AD to the process disturbance induced by different TAN concentrations. The overall performance of AD system was gradually optimized at the concentration of 3000mg/L TAN while when TAN reached 6000mg/L, an accumulation of propionate and butyrate was observed with a concomitant decrease of methane yield. At both concentration levels, the resistance and redundancy of hydrolytic and acidogenic bacteria can ensure their metabolic performance for substrate degradation. However, the total relative abundance of acetogens and methanogens at the low concentration level continued to increase, whereas a low increase rate and even a decrease in the total relative abundance was observed at the high level, suggesting the potential process inhibition. By further analyzing the functional gene changes in the two process stages, The methanogenesis and syntrophic acetate oxidation pathways showed resistance and redundancy under the ammonia stress, but the high concentration of TAN (6000mg/L) inhibited the expression of key genes ACADS and PCCA in the syntrophic degradation of butyrate and propionate. Therefore, the key contributor to the ammonia inhibition turned out to be acetogenesis.