Feng Gao, Zeng Yan, Wang Hui-Zhong, Chen Ya-Ting, Tang Yue-Qin
College of Architecture and Environment, Sichuan University, Chengdu, Sichuan, China.
Institute of New Energy and Low-Carbon Technology, Sichuan University, Chengdu, Sichuan, China.
Front Microbiol. 2023 Jan 6;13:1098814. doi: 10.3389/fmicb.2022.1098814. eCollection 2022.
Microorganisms in anaerobic digestion (AD) are easily affected by ammonia, especially acetoclastic methanogens. Thus, in ammonia-suppressed AD systems, acetate degradation is reported to be carried out mainly by the cooperation of syntrophic acetate oxidizers and hydrogenotrophic methanogens. Previous studies have revealed ammonia inhibition on microbial flora by AD performance, but the effect mechanism of ammonia on microbial metabolism remains poorly understood. In this study, we constructed a mesophilic chemostat fed with acetate as the sole carbon source, gradually increased the total ammonia nitrogen (TAN) concentration from 1 g L to 6 g L, and employed the 16S rRNA gene, metagenomics, and metatranscriptomics analysis to characterize the microbial community structure and metabolic behavior. The results showed that even at the TAN of 6 g L (pH 7.5), the methanogenesis kept normal, the biogas production was approximately 92% of that at TAN of 1 g L and the acetate degradation ratio reached 99%, suggesting the strong TAN tolerance of the microbial community enriched. 16S rRNA gene analysis suggested that the microbial community structure changed along with the TAN concentration. predominated in methanogens all the time, in which the dominant species was gradually replaced from to with the increased TAN. Dominant bacterial species also changed and showed a significant positive correlation with increased TAN. Meta-omics analysis showed that the absolute dominant microorganisms at TAN of 6 g L were and , both of which highly expressed genes for anti-oxidative stress. and the second dominant methanogen highly expressed both acetate cleavage and CO reduction pathways, suggesting the possibility that these two pathways contributed to methanogenesis together. and some other species in Firmicutes and Synergistetes were likely acetate oxidizers in the community as they highly expressed genes for syntrophic acetate oxidization, H generation, and electron transfer. These results suggested that as well as have strong ammonia tolerance and played critical roles in acetate degradation under ammonia-suppressed conditions. The achievements of the study would contribute to the regulation and management of the AD process.
厌氧消化（AD）中的微生物很容易受到氨的影响，尤其是乙酸裂解产甲烷菌。因此，在氨抑制的AD系统中，据报道乙酸盐的降解主要是通过互营乙酸氧化菌和氢营养型产甲烷菌的协同作用来进行的。以往的研究已经通过AD性能揭示了氨对微生物菌群的抑制作用，但氨对微生物代谢的作用机制仍知之甚少。在本研究中，我们构建了一个以乙酸盐作为唯一碳源的嗜温恒化器，将总氨氮（TAN）浓度从1 g/L逐渐提高到6 g/L，并采用16S rRNA基因、宏基因组学和宏转录组学分析来表征微生物群落结构和代谢行为。结果表明，即使在TAN为6 g/L（pH 7.5）时，产甲烷作用仍保持正常，沼气产量约为TAN为1 g/L时的92%，乙酸盐降解率达到99%，这表明富集的微生物群落对TAN具有很强的耐受性。16S rRNA基因分析表明，微生物群落结构随着TAN浓度的变化而改变。产甲烷菌中 一直占主导地位，其中优势物种随着TAN的增加逐渐从 被 取代。优势细菌物种也发生了变化， 与TAN的增加呈显著正相关。宏组学分析表明，TAN为6 g/L时的绝对优势微生物是 和 ，它们都高表达抗氧化应激基因。占第二位的优势产甲烷菌 和 都高表达乙酸盐裂解和CO还原途径，这表明这两条途径可能共同促进产甲烷作用。厚壁菌门和互养菌门中的 和其他一些物种可能是群落中的乙酸氧化菌，因为它们高表达互营乙酸氧化、H生成和电子传递的基因。这些结果表明， 和 具有很强的耐氨性，并且在氨抑制条件下的乙酸盐降解中发挥了关键作用。该研究成果将有助于AD过程的调控和管理。
