Abundance ofZetaproteobacteriawithin crustal fluids in back‐arc hydrothermal fields of the Southern Mariana Trough

Abstract

SummaryTo extend knowledge of subseafloor microbial communities within the oceanic crust, the abundance, diversity and composition of microbial communities in crustal fluids at back-arc hydrothermal fields of the Southern Mariana Trough (SMT) were investigated using culture-independent molecular techniques based on 16S rRNA gene sequences. Seafloor drilling was carried out at two hydrothermal fields, on-and off-ridge of the back-arc spreading centre of the SMT. 16S rRNA gene clone libraries for bacterial and archaeal communities were constructed from the fluid samples collected from the boreholes. Phylotypes related to Thiomicrospira in the Gammaproteobacteria (putative sulfide-oxidizers) and Mariprofundus in the Zetaproteobacteria (putative iron-oxidizers) were recovered from the fluid samples. A number of unique archaeal phylotypes were also recovered. Fluorescence in situ hybridization (FISH) analysis indicated the presence of active bacterial and archaeal populations in the fluids. The Zetaproteobacteria accounted for up to 32% of the total prokaryotic cell number as shown by FISH analysis using a specific probe designed in this study. Our results lead to the hypothesis that the Zetaproteobacteria play a role in iron oxidation within the oceanic crust.

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

“…The dominance of Betaproteobacteria in habitats adjacent to gastropod aggregates may be supported by organic compounds excreted from gastropods, because heterotrophy is a dominant lifestyle in Betaproteobacteria. A similar temporal change in microbial community composition was previously observed in samples collected from the SMT borehole (Kato et al 2009). This change may be due to long-term (yearscale) temporal fluctuation in the microbial community caused by a change in environmental factors.…”

“…Hydrothermal vents are surrounded by habitat zones of polychaetes, galatheid crabs (Shinkaia crosnieri), and bivalves (genus Bathymodiolus), in order of increasing distance from the vent, which may be due to the optimal hydrothermal mixing required to support the growth of these species. The hydrothermal fluid samples were taken from each SMT and MOT sampling area using a bag sampling system, a rotary clean seawater sampling system (Kato et al 2009), and a Niskin bottle (Table 6.2). The collected samples were immediately fixed for 6 h with 3.7 % neutralized formalin and stored at À80 C for analysis onshore.…”

A Compilation of the Stable Isotopic Compositions of Carbon, Nitrogen, and Sulfur in Soft Body Parts of Animals Collected from Deep-Sea Hydrothermal Vent and Methane Seep Fields: Variations in Energy Source and Importance of Subsurface Microbial Processes in the Sediment-Hosted Systems

“…10.1). The lack of clastic sediments in the hydrothermal fields reflects ammonium concentrations < 20 μM/kg (Kato et al 2009;de Ronde et al 2011;Gamo et al 2001), due to minimal contribution of sedimentary organic matter to the hydrothermal fluids. Bio-diversity of the animal communities observed at the Snail and Yamanaka sites in the South Mariana Trough was very low (Kojima and Watanabe, Chap.…”

Intra-Field Variation of Prokaryotic Communities On and Below the Seafloor in the Back-Arc Hydrothermal System of the Southern Mariana Trough

“…9), crustal fluids obtained from boreholes (Fapm1a, Fapm1b, Papm3, F2apm1), a natural vent fluid (Fnv) and ambient seawater (Pasw and Fasw) (Kato et al 2009b) in the SMT hydrothermal fields, i.e., Snail, Pika, Archaean, Kaiko and Yamanaka sites (Suppl. 24.1).…”

“…1). Numerous studies have characterized the prokaryotic community structures in various habitat types, such as hydrothermally active chimneys (e.g., Flores et al 2012a;Kato et al 2010;Kormas et al 2006;Nakagawa et al 2005;Schrenk et al 2003;Takai and Horikoshi 1999), inactive chimneys (Kato et al 2010;Suzuki et al 2004;Sylvan et al 2012), iron-rich mats (e.g., Davis and Moyer 2008;Fleming et al 2013;Forget et al 2010;Kato et al 2009a), and crustal fluids (Cowen et al 2003;Huber et al 2006;Kato et al 2009bKato et al , 2013Orcutt et al 2011), in various deep-sea hydrothermal fields. Through such studies, interfield variation between prokaryotic community structures in deep-sea hydrothermal system habitats has been revealed (e.g., Takai et al 2006;Flores et al 2012a).…”