Taiwan is situated in the subtropical region and its geographical location and topographical features contribute to a rich ecological diversity and scenic landscapes. We investigated the diversity of methanogens in different environments of Taiwan using a culture-dependent method. This report presents the characterization and taxonomy of six hydrogenotrophic methanogens obtained from cold seep sediments (strain FWC-SCC1^T and FWC-SCC3^T), marine sediments (strain CWC-02^T and YWC-01^T), estuarine sediments (strain Afa-1^T), and a hot spring well (strain Wushi-C6^T) in Taiwan. The proposed names of the six novel species are Methanoculleus frigidifontis (type strain FWC-SCC1^T=BCRC AR10056^T=NBRC 113993^T), Methanoculleus oceani (CWC-02^T=BCRC AR10055^T=NBRC 113992^T), Methanoculleus methanifontis (FWC-SCC3^T=BCRC AR10057^T=NBRC 113994^T), Methanoculleus nereidis (YWC-01^T=BCRC AR10060^T=NBRC 114597^T), Methanoculleus formosensis (Afa-1^T=BCRC AR10054^T=NBRC 113995^T), and Methanoculleus caldifontis (Wushi-06^T=BCRC AR10059^T= NBRC 114596^T).

We report the complete genome sequence of Anaerotignum sp. strain MB30-C6, which was isolated from the dehydrated sludge collected at the wastewater treatment plant of Sanming Steel Co. Ltd. in Fujian, China. The resulting genome of strain MB30-C6 is a single contig of 3,104,838 bp with 39.49% GC content.

A novel mesophilic, hydrogenotrophic methanogen, strain CWC-01^T, was isolated from the sediment sample of the piston core collected at station 3 at Good Weather Ridge area offshore southwestern Taiwan from ORI-902A cruise in 2009. Cells of strain CWC-01^T are rod-shaped, measuring 0.4–0.5 µm in width and 1.0–2.0 µm in length. Strain CWC-01^T utilizes formate and H₂/CO₂ to produce methane, but not secondary alcohol, methanol, ethanol, methylamines or acetate as catabolic substrates. The optimal growth conditions are 37 °C, 0.043 M NaCl and pH 6.3. Growth effectors tests indicate tryptone, but not acetate and yeast extract, could stimulate the growth of strain CWC-01. Phylogenetic analysis of 16S rRNA gene reveals that strain CWC-01^T is most closely related to Methanobacterium petrolearium Mic5c12^T, with 96.63% identity. Genome size of strain CWC-01^T is 1.98 Mb and it is the smallest genome size of genus. The genomic DNA G+C content obtained from the genome sequence of strain CWC-01^T is 44.15 mol%. Based on these phenotypic, phylogenetic and genomic analyses, we propose that strain CWC-01^T represents a novel species in genus Methanobacterium, for which the name Methanobacterium aridiramus sp. nov. is proposed. The type strain is CWC-01^T (=BCRC AR10053^T=NBRC 113991^T).

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 Paraescarpia formosa sp. nov. through morphological and phylogenetic analyses. The endosymbionts in the trunk of P. formosa 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 P. formosa 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, Desulfococcus and Desulfobulbus, 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 Sulfurovum and Sulfurimonas in phylum Epsilonbacteraeota were dominant. This study revealed the first investigation of microbiota in and around tubeworm P. formosa 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.

Here, we report the complete genome sequence of Bacteroidales bacterium strain MB20-C3-3 (=BCRC 81427) isolated from sewage sludge. The genome is 2,379,874 bp in length with a guanine and cytosine content of 40.0%. The genome of strain MB20-C3-3 was used for further species delineation and comparative genomic analyses.

Here, we report the complete genome sequence of Sedimentibacter sp. strain MB35-C1, which was isolated from sewage sludge at the Wastewater Treatment Plant of Sanming Steel Co. Ltd. in Fujian, China. The resulting genome of strain MB35-C1 is a single contig of 3,621,605 bp.