近岸海洋线虫与细菌、古菌的共现性及其对碳、氮循环的影响

Effect of co-occurrence of marine nematodes and microbes on carbon and nitrogen cycles in coastal sediments

摘要:

[目的]初步探究海洋线虫与微生物的相互作用对碳、氮循环的影响。[方法]利用16S rRNA和18S rRNA基因高通量测序方法，对33个近岸沉积物样品中细菌、古菌和真核生物的多样性进行调查；对海洋线虫与细菌、海洋线虫与古菌的共现性进行网络分析，并采用Spearman统计学方法，识别出与海洋线虫共现性呈显著相关性的微生物种类。[结果]在夏季，红树林和潮间带泥滩样品中线虫OTU平均相对丰度基本呈随深度增加而递减趋势；冬季的红树林样品中发现相类似变化规律，只有在冬季潮间带泥滩样品中线虫OTU平均相对丰度在深层较高于表层。相对丰度最高的海洋线虫隶属于单宫目（47%）、色矛目（19%）、刺嘴目（16%）和垫刃目（9%），它们与热源体古菌、深古菌、γ-和δ-变形菌等微生物有显著正/负相关关系。[结论]在香港米埔湿地沉积物中，与相对丰度最高的5种线虫显著相关的几大类微生物均在碳、氮、硫等元素循环方面起十分重要的作用，暗示海洋线虫与微生物潜在的相互作用对元素地球化学循环具有重要影响。研究结果有助于深入了解线虫在生态系统中未被揭示的生态功能，有助于更清晰地认识海洋线虫在底栖生态系统中所扮演的角色。

Abstract:

[Objective] This study is aimed to investigate the interaction effects of marine free-living nematodes and microbes on carbon and nitrogen cycles in coastal sediments. [Methods] We used 16S rRNA and 18S rRNA high-throughput sequencing technology to inspect the diversity and community of bacteria, archaea and eukaryotes in 33 coastal sediment samples. The Spearman correlation method was adapted to analyze the co-occurrence pattern between marine nematodes and microbes (bacteria and archaea), to recognize the microbial group with significant correlation with nematodes. [Results] In summer, the average relative abundance of nematode OTUs decreased with the increasing depths both in mangrove and intertidal mudflat sediments. Similar pattern was discovered in winter samples with one exception that the averaged relative abundance of nematode OTUs in deeper layer was significantly higher than that in upper layer. The five most abundant marine nematode OTUs belong to Monhysterida (47%), Chromadorida (19%), Enoplia (16%) and Tylenchida (9%). Those OTUs are significantly correlated with Thermoplasmata, Bathyarchaeota, gamma-and delta-Proteobacteria. [Conclusion] In the wetland sediments sampled from Mai Po Nature Reserve of Hong Kong, the microbes those have significant correlation with nematodes play important roles in carbon, nitrogen and sulfur cycles. It implies that the potential interaction effects between marine nematodes and microbes have crucial impacts on biogeochemical cycles. Our results could help us to uncover the ecological function of nematodes in the environments, to better understand the roles of marine nematodes in the benthic ecosystems.