Complex bacterial diversity of Guaymas Basin hydrothermal sediments revealed by synthetic long-read sequencing (LoopSeq)

Hydrothermal vents host phylogenetically diverse and physiologically complex microbial communities. Previous studies of microbial community structure in hydrothermal sediments have typically used short-read sequencing approaches. To address these shortcomings, we use LoopSeq, a high-throughput synthetic long-read sequencing method that has yielded promising results in analyses of microbial ecosystems, such as the human gut microbiome. In this study, LoopSeq is used to obtain near-full length bacterial 16S rRNA gene sequences from hydrothermal sediments in Guaymas Basin. Based on these sequences, high-quality alignments and phylogenetic analyses provided new insights into the taxonomic diversity of sulfur-cycling microorganisms and their distribution along a lateral hydrothermal gradient. In general, LoopSeq-derived 16S rRNA gene sequences aligned consistently with reference sequences in GenBank; however, chimeras were prevalent in sequences as affiliated with the thermophilic Candidatus Desulfofervidus and Thermodesulfobacterium , and in smaller numbers within the sulfur-oxidizing family Beggiatoaceae . Our analysis of sediments along well-documented thermal and geochemical gradients show how sulfur-cycling bacteria of different taxonomic groups persist as active catalysts of the sulfur cycle in varying combinations throughout surficial hydrothermal sediments in the Guaymas Basin.