Bacterial Diversity and Community Structure of Lithotrophically-Driven Microbial Mats from the Mariana Arc and Back-Arc

The Mariana region exhibits a rich array of hydrothermal venting conditions in a complex geological setting, which provides a natural laboratory to study the influence of local environmental conditions on microbial community structure as well large-scale patterns in microbial biogeography. We used high-throughput amplicon sequencing of the bacterial SSU rRNA gene from 22 microbial mats collected from four hydrothermally active locations along the Mariana Arc and back-arc to explore the structure of lithotrophically-based microbial mat communities in order to better assess the hypothesis that these communities represent hotspots of microbial diversity. The vent effluent was classified as iron- or sulfur-rich corresponding with two distinct community types, dominated by either Zetaproteobacteria or Epsilonproteobacteria, respectively. The Zetaproteobacterial-based communities had the highest richness and diversity, which supports the hypothesis that Zetaproteobacteria are ecosystem engineers. The Epsilonproteobacteria-dominated mats were less abundant and split into two groups based on the prevalence of the genera Sulfurovum/Sulfurimonas or Thioreductor/Lebetimonas, which oxidize or reduce sulfur compounds, respectively. In addition, we also compare two sampling techniques, showing that higher diversity in microbial mats is associated with bulk sampling compared to fine-scale sampling. Overall, we present a comprehensive analysis and new insights into community structure and diversity of the lithotrophically-driven microbial mats from a hydrothermal region associated with high microbial biodiversity.