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

Abstract

Subseafloor microbes beneath active hydrothermal vents are thought to live near the upper temperature limit for life on Earth. We drilled and cored the Iheya North hydrothermal field in the MidOkinawa Trough, and examined the phylogenetic compositions and the products of metabolic functions of sub-vent microbial communities. We detected microbial cells, metabolic activities and molecular signatures only in the shallow sediments down to 15.8 m below the seafloor at a moderately distant drilling site from the active hydrothermal vents (450 m). At the drilling site, the profiles of methane and sulfate concentrations and the δ 13 C and δD isotopic compositions of methane suggested the laterally flowing hydrothermal fluids and the in situ microbial anaerobic methane oxidation. In situ measurements during the drilling constrain the current bottom temperature of the microbially habitable zone to~45°C. However, in the past, higher temperatures of 106-198°C were possible at the depth, as estimated from geochemical thermometry on hydrothermally altered clay minerals. The 16S rRNA gene phylotypes found in the deepest habitable zone are related to those of thermophiles, although sequences typical of known hyperthermophilic microbes were absent from the entire core. Overall our results shed new light on the distribution and composition of the boundary microbial community close to the high-temperature limit for habitability in the subseafloor environment of a hydrothermal field.

Marine Subsurface Microbial Community Shifts Across a Hydrothermal Gradient in Okinawa Trough Sediments

“…The overall heterogeneous community composition in these sediments exhibits similarities to other studied marine sediments, and the results of this study complement the findings from Yanagawa and colleagues [43]. Many taxa identified here, for example, Chloroflexi and Bathyarchaeota, have ubiquitous distributions in marine subsurface habitats.…”

Faecal freezing preservation period influences colonization ability for faecal microbiota transplantation

“…These results indicate that boiling selects for Burkholderiales, which was previously reported as a predominant taxon in hydrothermal vents (Yanagawa et al . ). Consequently, it was likely that the 16S rRNA‐based PMA microbiome method in the present study was reliable for differentiation between living and dead cells.…”

Diversity and metabolism of prokaryotic chemoautotrophs and their interactions with deep-sea hydrothermal environments

“…但没有检测到Thermococcales, Methanococcales, Ar-chaeoglobales等超高温菌的存在 [38] ; 在该热液区10 m 以内的沉积物中, Chloroflexi门细菌为主, 在较深的 高温黏土层中(15 m, 55℃), 泉古菌类群(Crenarchaeotic Group)和甲烷氧化古菌丰度增加 [39] . [40] .…”