Southwest Indian Ridge (SWIR) is a typical oceanic ultraslow spreading ridge with intensive hydrothermal activities. The microbial communities in hydrothermal fields including primary producers to support the entire ecosystem by utilizing geochemical energy generated from rock-seawater interactions. Here we have examined the microbial community structures on four hydrothermal vents from SWIR, representing distinct characteristics in terms of temperature, pH and metal compositions, by using Illumina sequencing of the 16S small subunit ribosomal RNA (rRNA) genes, to correlate bacterial and archaeal populations with the nature of the vents influenced by ultraslow spreading features. Epsilon-, Gamma-, Alpha-, and Deltaproteobacteria and members of the phylum Bacteroidetes and Planctomycetes, as well as Thaumarchaeota, Woesearchaeota, and Euryarchaeota were dominant in all the samples. Both bacterial and archaeal community structures showed distinguished patterns compared to those in the fast-spreading East Pacific Ridge or the slow-spreading Mid-Atlantic Ridge as previously reported. Furthermore, within SWIR, the microbial communities are highly correlated with the local temperatures. For example, the sulfur-oxidizing bacteria were dominant within bacteria from low-temperature vents, but were not represented as the dominating group recovered from high temperature (over 300°C) venting chimneys in SWIR. Meanwhile, Thaumarchaeota, the ammonium oxidizing archaea, only showed high relative abundance of amplicons in the vents with high-temperature in SWIR. These findings provide insights on the microbial community in ultraslow spreading hydrothermal fields, and therefore assist us in the understanding of geochemical cycling therein.

中文翻译：

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超慢速蔓延的西南印第安海脊深海热液喷口的微生物群落结构。

西南印第安海岭（SWIR）是典型的海洋超慢扩散海脊，具有强烈的热液活动。热液领域中的微生物群落，包括初级生产者，通过利用岩石-海水相互作用产生的地球化学能来支持整个生态系统。在这里，我们通过使用16S小亚基核糖体RNA（rRNA）基因的Illumina测序，检查了来自SWIR的四个热液喷口的微生物群落结构，它们在温度，pH和金属成分方面表现出不同的特征，以关联细菌和古细菌种群通风口的性质受超慢扩散特性的影响。Epsilon，Gamma，Alpha和Deltaproteobacteria以及拟杆菌门和扁平菌门的成员，以及Thaumarchaeota，Woesearchaeota，和Euryarchaeota在所有样本中占主导地位。与先前报道的快速扩散的东太平洋海岭或缓慢扩散的中大西洋海岭相比，细菌和古细菌群落结构均显示出独特的模式。此外，在SWIR中，微生物群落与当地温度高度相关。例如，硫氧化细菌在低温通风口的细菌中占主导地位，但不代表从SWIR中高温（超过300°C）通风烟囱中回收的支配基团。同时，铵氧化性古细菌Thaumarchaeota在SWIR中仅在高温喷口中显示出较高的扩增子相对丰度。这些发现为超慢扩散热液田中的微生物群落提供了见识，