北京莲花池趋磁细菌的群落多样性研究

Morphological and Phylogenetic Diversity of Magnetotactic Bacteria in Pond Lianhua, Beijing

趋磁细菌是一类在细胞内合成磁铁矿(Fe_3O_4)或胶黄铁矿(Fe_3S_4)磁小体的微生物,广泛分布在水环境和沉积环境,在铁、硫、碳、氮、磷等元素的生物地球化学循环中发挥重要作用.趋磁细菌培养条件苛刻,目前对环境趋磁细菌的多样性和生理代谢特征等还有待系统深入的研究.本研究综合利用电子显微镜、能谱分析和分子生态学等技术方法,对北京地区莲花池沉积物中趋磁细菌的形态多样性、细胞元素分布特征和系统发育多样性等进行了系统分析.光学显微镜观察和电子显微镜分析显示莲花池中存在大量趋磁细菌(～10~3～10~4细胞/mL),从形态上主要分为球形和弧形两种,在细胞内富含铁、硫、镁等元素.基于16S rRNA基因的系统发育研究共发现了7个新类群,分别属于(Proteobacteria)中的α-变形菌纲和γ-变形菌纲,其中属于α-变形菌纲的5个类群与已知趋磁细菌序列最相似(≥91%).本研究结果有助于更好地认识自然界趋磁细菌的群落多样性和地质环境功能.

Magnetotactic bacteria（MTB） biomineralize intracellular magnetite（Fe3 O4） and/or greigite（Fe3 S4） magnetosomes. They are widely distributed in aquatic environments and play important roles in the biogeochemical cycles of Fe, S, C, N and P. Due to their difficulty of cultivation our knowledge on the diversity and environmental function of MTB remains very limited. Here, we have characterized a group of uncultivated MTB from Pond Lianhua in Beijing, China. Light and scanning electron microscopy shows coccoid and vibrioid in cell morphologies. Transmission electron microscopy and energy dispersive spectroscopy indicate that the mineral phase of magnetosomes is magnetite and that some cells of MTB contain large amount of intracellular sulfur and magnesium. 16 S rRNA gene-based cultivation-independent analysis has identified seven operational taxonomic units（OTUs） belonging to the Alphaproteobacteria and Gammaproteobacteria in the Proteobacteria phylum. Taken together, our results highlight a high diversity of MTB in environment that may contribute to the geochemical cycling of iron and other elements.