小型城市湿地微生物组及其固碳基因潜力分析

Microbiome and its genetic potential for carbon fixation in small urban wetlands

摘要:

小型城市湿地分布广泛，易受人类活动的影响，是重要的碳源和碳汇。微生物在碳循环中起重要驱动作用，但目前对小型城市湿地中原核生物多样性及其在固碳和碳代谢中的作用研究较少。为深入了解小型城市湿地中微生物驱动的碳循环过程，解析微生物群落和相关功能类群的组成，本研究系统分析了湖州市3处小型湿地微生物组的组成、元素代谢途径及与生境理化性质的联系，并与若尔盖高原自然湿地进行了比较。基于16S rRNA基因扩增子和宏基因组测序分析了物种及功能组成，组装出60个中高质量的基因组(metagenome-assembled genomes, MAGs)，包括55个细菌和5个古菌物种，分析了其在2种类型湿地中的分布情况和推动元素循环的功能潜力，尤其关注了固碳途径。发现数种细菌的基因组几乎编码了完整的卡尔文循环、还原三羧酸循环、还原乙酰辅酶A途径以及还原型甘氨酸途径，其中包括隶属于Syntrophorhabdus属(脱硫杆菌门)和UBA4417属(拟杆菌门)的潜在的新型固碳细菌，且这些菌种在湿地微生物组中具有相对较高的丰度。揭示这些功能类群推动元素循环的基因潜力，对增强小型城市湿地的碳汇功能具有重要的科学意义。

Abstract:

Small urban wetlands are widely distributed and susceptible to human activities, serving as important sources and sinks of carbon. Microorganisms play a crucial role in carbon cycle, while limited studies have been conducted on the microbial diversity in small urban wetlands and the functions of microbiome in carbon fixation and metabolism. To probe into the microbiome-driven carbon cycling in small urban wetlands and dissect the composition and functional groups of microbiome, we analyzed the relationships between the microbiome structure, element metabolism pathways, and habitat physicochemical properties in sediment samples across three small wetlands in Huzhou City, and compared them with natural wetlands in the Zoige wetland. High-throughput sequencing of 16S rRNA gene amplicons and metagenomics was employed to determine the species and functional groups. Sixty medium to high-quality metagenome-assembled genomes (MAGs) were constructed, including 55 bacterial and 5 archaeal taxa, and their potential in driving elemental cycles were analyzed, with a focus on carbon fixation. Several bacterial species were found to encode a nearly complete carbon fixation pathway, including the Calvin cycle, the reductive tricarboxylic acid cycle, the Wood-Ljungdahl pathway, and the reductive glycine pathway. There were several potential novel carbon-fixing bacterial members, such as those belonging to Syntrophorhabdus (Desulfobacterota) and UBA4417 (Bacteroidetes), which had high relative abundance in the wetland microbiome. Unveiling the genetic potential of these functional groups to facilitate element cycling is of great scientific importance for enhancing the carbon sequestration capacity of small urban wetlands.