Prokaryotic community structure and diversity in the sediment of Kazan mud volcano

We investigated 16S rRNA gene diversity at a high sediment depth resolution (every 5 cm, top 30 cm) in an active site of the Kazan mud volcano, East Mediterranean Sea. A total of 242 archaeal and 374 bacterial clones were analysed, which were attributed to 38 and 205 unique phylotypes, respectively (>=98% similarity). Most of the archaeal phylotypes were related to ANME-1, -2 and -3 members originating from habitats where anaerobic oxidation of methane (AOM) occurs, although they occurred in sediment layers with no apparent AOM (below the sulphate depletion depth). Proteobacteria were the most abundant and diverse bacterial group, with the Gammaproteobacteria dominating in most sediment layers and these were related to phylotypes involved in methane cycling. The Deltaproteobacteria included several of the sulphate-reducers related to AOM. The rest of the bacterial phylotypes belonged to 15 known phyla and three unaffiliated groups, with representatives from similar habitats. Diversity index H was in the range 0.56-1.73 and 1.47-3.82 for Archaea and Bacteria, respectively, revealing different depth patterns for the two groups. At 15 and 20 cm below the sea floor, the prokaryotic communities were highly similar, hosting AOM-specific Archaea and Bacteria. Our study revealed different dominant phyla in proximate sediment layers.

本研究针对东地中海喀山泥火山（Kazan mud volcano）活动位点，以高分辨率沉积物深度梯度（每5 cm采样一层，采样深度达表层下30 cm）开展了16S核糖体RNA基因（16S rRNA gene）多样性分析。共获得242个古菌克隆与374个细菌克隆，基于≥98%的序列相似性阈值，二者分别归属于38个与205个独特系统型（phylotype）。绝大多数古菌系统型与产甲烷厌氧氧化（anaerobic oxidation of methane, AOM）生境来源的厌氧甲烷氧化古菌（ANME）-1、-2及-3类群具有亲缘关系，尽管这些类群存在于硫酸盐耗尽层以下的无明显AOM活性的沉积物层中。变形菌门（Proteobacteria）是丰度与多样性最高的细菌类群，其中γ-变形菌纲（Gammaproteobacteria）在多数沉积物层中占主导地位，其亲缘类群均参与甲烷循环过程。δ-变形菌纲（Deltaproteobacteria）包含多个与AOM相关的硫酸盐还原菌类群。其余细菌系统型隶属于15个已知菌门与3个未分类类群，其代表类群均分离自同类生境。古菌与细菌的多样性指数H分别处于0.56~1.73与1.47~3.82区间，二者呈现出截然不同的深度分布模式。在海底以下15 cm与20 cm处，原核生物群落结构高度相似，均携带AOM特异性的古菌与细菌类群。本研究揭示了相邻沉积物层中存在不同的优势菌门。