Microbial Communities in and Around the Siboglinid Tubeworms from the South Yungan East Ridge Cold Seep Offshore Southwestern Taiwan at the Northern South China Sea

To date, only a few microbial community studies of cold seeps at the South China Sea (SCS) have been reported. The cold seep dominated by tubeworms was discovered at South Yungan East Ridge (SYER) offshore southwestern Taiwan by miniROV. The tubeworms were identified and proposed as <i>Paraescarpia formosa</i> sp. nov. through morphological and phylogenetic analyses. The endosymbionts in the trunk of <i>P. formosa</i> analyzed by a 16S rRNA gene clone library represented only one phylotype, which belonged to the family Sedimenticolaceae in Gammaproteobacteria. In addition, the archaeal and bacterial communities in the habitat of tubeworm <i>P. formosa</i> were investigated by using high-phylogenetic-resolution full-length 16S rRNA gene amplicon sequencing. The results showed that anerobic methane-oxidizing archaea (ANME)-1b was most abundant and ANME-2ab was minor in a consortia of the anerobic oxidation of methane (AOM). The known sulfate-reducing bacteria (SRB) partners in AOM consortia, such as SEEP-SRB1, -SRB2, and -SRB4, <i>Desulfococcus</i> and <i>Desulfobulbus</i>, occurred in a small population (0–5.7%) at the SYER cold seep, and it was suggested that ANME-1b and ANME-2ab might be coupled with multiple SRB in AOM consortia. Besides AOM consortia, various methanogenic archaea, including Bathyarchaeota (Subgroup-8), Methanocellales, Methanomicrobiales, Methanosarcinales, Methanofastidiosales and Methanomassiliicoccales, were identified, and sulfur-oxidizing bacteria <i>Sulfurovum</i> and <i>Sulfurimonas</i> in phylum Epsilonbacteraeota were dominant. This study revealed the first investigation of microbiota in and around tubeworm <i>P. formosa</i> discovered at the SYER cold seep offshore southwestern Taiwan. We could gain insights into the chemosynthetic communities in the deep sea, especially regarding the cold seep ecosystems at the SCS.