Archaeal Diversity and Distribution along Thermal and Geochemical Gradients in Hydrothermal Sediments at the Yonaguni Knoll IV Hydrothermal Field in the Southern Okinawa Trough

Abstract

Deep-sea hydrothermal activity results in diverse physical and chemical environments for the resident microbial communities. Using cultivation techniques and culture-independent molecular analyses, diverse lineages of archaea and bacteria have so far been observed from chimney structures, retrieved in situ colonization systems settled in or on the hydrothermal conduit, microbial mats, sediments, and chemosynthetic macrofaunal bodies (19,35,62). Especially in the domain Archaea, most of lineages derived from hydrothermal environments have not yet been cultivated, and little is known about their physiological and metabolic traits.

Defining boundaries for the distribution of microbial communities beneath the sediment-buried, hydrothermally active seafloor

“…They were also detected as the predominant population (99% of the total archaeal sequences) in the near-surface sediment at 1 mbsf in Hole C0013B, which is the only sample containing detectable 16S rRNA genes at Site C0013 (data not shown). The HWCGIV sequences have previously been reported in deep-sea hydrothermal vent habitats (Schrenk et al, 2003;Nunoura et al, 2010;Yoshida-Takashima et al, 2012) and in a hightemperature zone at 141.1 mbsf at Site C0017 (Yanagawa et al, 2014).…”

“…In this study, all of the pore-water geochemical analyses, metabolic activity measurements and cellular and molecular microbial community analyses indicated the occurrence of functionally active microbial communities dominated by AOM populations in the relatively shallow subseafloor habitats down to 15.8 mbsf in Hole C0014G. Several studies have examined the abundance, phylogenetic diversity and function of AOM populations associated with seafloor hydrothermal activity in the Guaymas Basin and Yonaguni Knoll IV fields (Teske et al, 2002;Nunoura et al, 2010;Yanagawa et al, 2013a;Dowell et al, 2016). Because these investigations have focused on the shallow sediments just beneath the seafloor, where the diffusive mixing of hydrothermal fluids and seawater likely characterizes the geochemical environments, there remains a lack of knowledge on the subseafloor AOM communities associated with hydrogeologically controlled advection and the partitioning and mixing processes of hydrothermal fluids and infiltrated seawater near deep-sea vents.…”

“…Several studies have further addressed the potential microbial habitats beneath the seafloor hydrothermal vents, the so-called 'sub-vent biosphere', and have indicated the possible occurrence of functionally active and metabolically diverse (hyper-)thermophilic microbial communities associated with shallow subseafloor hydrothermal fluids and mineral deposits (Deming and Baross, 1993;Delaney et al, 1998;Summit and Baross, 1998;Huber et al, 2002Huber et al, , 2003. The compositions and functions of the sub-vent microbial communities have been inferred from culture-dependent and culture-independent analyses of microbial communities in (i) in situ growth chambers placed in hydrothermal fluid flows (Karl et al, 1988;Reysenbach et al, 2000;Corre et al, 2001;Takai et al, 2004), (ii) crustal fluids collected directly from the shallow subseafloor environments (~10 m below the seafloor [mbsf]) via seafloor drilling or probe insertion (Cowen et al, 2003;Higashi et al, 2004;Huber et al, 2006;Kato et al, 2009;Orcutt et al, 2011), (iii) hydrothermal sediments (Teske et al, 2002;Dhillon et al, 2005;Nunoura et al, 2010;Teske et al, 2014;Dowell et al, 2016;Teske et al, 2016) and (iv) chimney structures of active hydrothermal vents (Takai et al, 2001;Schrenk et al, 2003;Nakagawa et al, 2005). These studies found that mesophilic, thermophilic and hyperthermophilic members of Epsilonproteobacteria, Gammaproteobacteria, Aquificales, Thermococcales and Methanococales were the potentially predominant microbial components in the sub-vent biosphere.…”

Saturated CO<sub>2</sub> inhibits microbial processes in CO<sub>2</sub>-vented deep-sea sediments

“…Besides their high CO 2 content, the hydrothermal fluids exhibit a wide variation in gas composition including H 2 , CH 4 , H 2 S and NH 3 . Previous studies have focussed on the distribution of bacterial and archaeal communities of the Yonaguni Knoll IV hydrothermal sediments and overlying bottom waters (Inagaki et al, 2006;Yanagawa et al, 2012;Nunoura et al, 2010). Here we have investigated the biogeochemistry of the CO 2 vented sediments, focussing on the distribution of microbial aerobic and anaerobic respiration pathways.…”

Quantification of Microbial Communities in Hydrothermal Vent Habitats of the Southern Mariana Trough and the Mid-Okinawa Trough

“…In particular, reduced compounds such as H 2 , CH 4 , HS À , and Fe 2+ are not only essential energy sources for chemolithotrophs but also factors that control the composition and density of the microbial community. Previous studies have investigated habitat components, for example, the boundary zone (interface) between hydrothermal fluid and ambient seawater, including low-temperature diffusive flow (Holden et al 1998;Huber et al 2002Huber et al , 2003Perner et al 2007), chimney structures (Schrenk et al 2003;Takai et al 2001), and hydrothermal sediments (Nunoura et al 2010;Teske et al 2002;Yanagawa et al 2013). These studies demonstrated the prevalence of Gammaproteobacteria, Deltaproteobacteria, Epsilonproteobacteria, Bacteroidetes, Firmicutes, and various candidate divisions in the hydrothermal system.…”