Data_Sheet_1_Immediate Effects of Ammonia Shock on Transcription and Composition of a Biogas Reactor Microbiome.pdf

The biotechnological process of biogas production from organic material is carried out by a diverse microbial community under anaerobic conditions. However, the complex and sensitive microbial network present in anaerobic degradation of organic material can be disturbed by increased ammonia concentration introduced into the system by protein-rich substrates and imbalanced feeding. Here, we report on a simulated increase of ammonia concentration in a fed batch lab-scale biogas reactor experiment. Two treatment conditions were used simulating total ammonia nitrogen concentrations of 4.9 and 8.0 g/L with four replicate reactors. Each reactor was monitored concerning methane generation and microbial composition using 16S rRNA gene amplicon sequencing, while the transcriptional activity of the overall process was investigated by metatranscriptomic analysis. This allowed investigating the response of the microbial community in terms of species composition and transcriptional activity to a rapid upshift to high ammonia conditions. Clostridia and Methanomicrobiales dominated the microbial community throughout the entire experiment under both experimental conditions, while Methanosarcinales were only present in minor abundance. Transcription analysis demonstrated clostridial dominance with respect to genes encoding for enzymes of the hydrolysis step (cellulase, EC 3.2.1.4) as well as dominance of key genes for enzymes of the methanogenic pathway (methyl-CoM reductase, EC 2.8.4.1; heterodisulfide reductase, EC 1.8.98.1). Upon ammonia shock, the selected marker genes showed significant changes in transcriptional activity. Cellulose hydrolysis as well as methanogenesis were significantly reduced at high ammonia concentrations as indicated by reduced transcription levels of the corresponding genes. Based on these experiments we concluded that, apart from the methanogenic archaea, hydrolytic cellulose-degrading microorganisms are negatively affected by high ammonia concentrations. Further, Acholeplasma and Erysipelotrichia showed lower abundance under increased ammonia concentrations and thus might serve as indicator species for an earlier detection in order to counteract against ammonia crises.

有机物质生物气生产的生物技术过程是在厌氧条件下由多种微生物群落共同完成的。然而，存在于有机物质厌氧降解过程中的复杂且敏感的微生物网络，可能因富含蛋白质的底物引入系统中的氨浓度增加及不均衡的投料而受到干扰。在本研究中，我们报告了一项模拟在分批投料的实验室规模生物气反应器实验中氨浓度增加的情况。实验中采用了两种处理条件，分别模拟了总氨氮浓度为4.9和8.0克/升的四种重复反应器。每个反应器均通过16S rRNA基因扩增子测序对甲烷生成和微生物组成进行监测，同时通过宏转录组分析研究了整个过程的转录活性，从而探究微生物群落对高氨条件快速转变的物种组成和转录活性响应。在实验的整个过程中，梭菌门和甲烷微菌门在两种实验条件下均占主导地位，而甲烷球菌门仅以少量存在。转录分析显示，在厌氧步骤中编码酶类（如纤维素酶，EC 3.2.1.4）的关键基因以及甲烷生成途径中关键酶（如甲基辅酶M还原酶，EC 2.8.4.1；异二硫化物还原酶，EC 1.8.98.1）的基因均表现出梭菌门的显著优势。在氨冲击下，选定的标记基因在转录活性上发生了显著变化。在较高氨浓度下，纤维素水解和甲烷生成均显著降低，如相应基因转录水平的降低所指示。基于这些实验，我们得出结论：除了产甲烷古菌外，水解纤维素降解微生物也受到高氨浓度的负影响。此外，在增加的氨浓度下，Acholeplasma和Erysipelotrichia的丰度降低，因此它们可能作为早期检测的指示物种，以应对氨危机。