Niche differentiation among mat-forming, sulfide-oxidizing bacteria in chemosynthetic ecosystems of the Nile Deep Sea Fan (Eastern Mediterranean Sea)@en

Sulfidic muds of cold seeps on the Nile Deep Sea Fan are populated by different types of mat-forming sulfide-oxidizing bacteria. The predominant sulfide oxidizers of three different mats were identified by microscopic and phylogenetic analyses as (i) Arcobacter species producing cotton-ball-like sulfur precipitates, (ii) large filamentous sulfur bacteria including Beggiatoa species, or (iii) single, spherical cells resembling Thiomargarita species. High resolution in situ microprofiles revealed different geochemical settings selecting for different mat types. Arcobacter mats occurred where oxygen and sulfide overlapped at the bottom water interface. Filamentous sulfide oxidizers were associated with non-overlapping, steep gradients of oxygen and sulfide. A dense population of Thiomargarita was favored by temporarily changing supplies of oxygen and sulfide. These results indicate that the decisive factors in selecting for different mat-forming bacteria within one deep-sea province are spatial or temporal variations in energy supply. Furthermore, the occurrence of Arcobacter spp.-related 16S rRNA genes in the sediments below all three types of mats, as well as on top of brine lakes of the Nile Deep Sea Fan, indicates that this group of sulfide oxidizers can switch between different life modes depending on the geobiochemical habitat setting.尼罗河深海扇（Nile Deep Sea Fan）冷泉的硫化质沉积物中，栖息着多种形成菌膜的硫化物氧化细菌。通过显微观察与系统发育分析，三种不同菌膜的优势硫化物氧化细菌被鉴定为：(i) 可产生棉球状硫沉淀物的弓形杆菌属（Arcobacter）物种；(ii) 涵盖贝日阿托氏菌属（Beggiatoa）物种的大型丝状硫细菌；(iii) 形态近似嗜硫珠菌属（Thiomargarita）的单个球形细胞。高分辨率原位微剖面研究显示，不同的地球化学环境会筛选出对应特征的菌膜类群。弓形杆菌属菌膜多见于氧与硫化物在底水界面发生重叠的区域；丝状硫化物氧化细菌则与氧和硫化物呈非重叠式陡峭梯度的生境相关联；高密度的嗜硫珠菌属种群则更适应氧与硫化物供给呈周期性变化的环境。上述结果表明，在同一深海区域内，调控不同菌膜形成细菌类群的决定性因素为能量供给的空间或时间变异。此外，在三种菌膜下方的沉积物以及尼罗河深海扇（Nile Deep Sea Fan）卤水湖顶部均检出与弓形杆菌属相关的16S rRNA基因，这表明该类硫化物氧化细菌可根据地球生物化学生境条件，在不同生活模式间灵活切换。