ABSTRACT
Marine sediments contain eukaryotic DNA deposited from overlying water columns. However, a large proportion of deposited eukaryotic DNA is aerobically biodegraded in shallow marine sediments. Cold seep sediments are often anaerobic near the sediment-water interface, so eukaryotic DNA in such sediments is expected to be preserved. We investigated deeply buried marine sediments in the Japan Sea, where a methane hydrate deposit is associated with cold seeps. Quantitative PCR analysis revealed the reproducible recovery of eukaryotic DNA in marine sediments at depths up to 31.0 m in the vicinity of the methane hydrate deposit. In contrast, the reproducible recovery of eukaryotic DNA was limited to a shallow depth (8.3 m) in marine sediments not adjacent to the methane hydrate deposit in the same area. Pyrosequencing of an 18S rRNA gene variable region generated 1,276-3,307 reads per sample, which was sufficient to cover the biodiversity based on rarefaction curves. Phylogenetic analysis revealed that most of the eukaryotic DNA originated from radiolarian genera of the class Chaunacanthida, which have SrSO4 skeletons, the sea grass genus Zostera, and the seaweed genus Sargassum. Eukaryotic DNA originating from other planktonic fauna and land plants was also detected. Diatom sequences closely related to Thalassiosira spp., indicative of cold climates, were obtained from sediments deposited during the last glacial period (MIS-2). Plant sequences of the genera Alnus, Micromonas, and Ulmus were found in sediments deposited during the warm interstadial period (MIS-3). These results suggest the long-term persistence of eukaryotic DNA from terrestrial and aquatic sources in marine sediments associated with cold seeps, and that the genetic information from eukaryotic DNA from deeply buried marine sediments associated with cold seeps can be used to reconstruct environments and ecosystems from the past.
Subject(s)
Biodiversity , Eukaryota/isolation & purification , Geologic Sediments/chemistry , Methane/analysis , Cold Temperature , Eukaryota/classification , Eukaryota/genetics , Eukaryota/metabolism , Japan , Oceans and Seas , Phylogeny , Plants/genetics , RNA, Ribosomal, 18S/analysis , RNA, Ribosomal, 18S/genetics , Sargassum/genetics , Sargassum/isolation & purification , Sequence Analysis, DNAABSTRACT
Microbial life inhabits deeply buried marine sediments, but the extent of this vast ecosystem remains poorly constrained. Here we provide evidence for the existence of microbial communities in ~40° to 60°C sediment associated with lignite coal beds at ~1.5 to 2.5 km below the seafloor in the Pacific Ocean off Japan. Microbial methanogenesis was indicated by the isotopic compositions of methane and carbon dioxide, biomarkers, cultivation data, and gas compositions. Concentrations of indigenous microbial cells below 1.5 km ranged from <10 to ~10(4) cells cm(-3). Peak concentrations occurred in lignite layers, where communities differed markedly from shallower subseafloor communities and instead resembled organotrophic communities in forest soils. This suggests that terrigenous sediments retain indigenous community members tens of millions of years after burial in the seabed.
Subject(s)
Aquatic Organisms/classification , Archaea/classification , Bacteria/classification , Coal/microbiology , Geologic Sediments/microbiology , Microbial Consortia , Seawater/microbiology , Aquatic Organisms/genetics , Aquatic Organisms/metabolism , Archaea/genetics , Archaea/metabolism , Bacteria/genetics , Bacteria/metabolism , Biomarkers/metabolism , Carbon Dioxide/metabolism , Japan , Methane/metabolism , Methanococcus/classification , Methanococcus/genetics , Methanococcus/metabolism , Methanosarcina barkeri/classification , Methanosarcina barkeri/genetics , Methanosarcina barkeri/metabolism , Pacific OceanABSTRACT
Tests for DM using the 75 g OGTT method (NDDG diagnostic criteria) were performed on 3145 persons living in rural areas of 8 different geographical regions of Japan (from Tohoku to Kyushu regions). Considerable regional difference was observed with western Japan tending to have higher DM and IGT rates than eastern Japan. The DM and IGT prevalence rates (for rural areas in Japan) were 3.9% and 6.9% respectively, and the DM detection rate was 2.8%. Comparison between normals and disturbance of glucose tolerance group (DM and IGT) on the basis of risk factors for atherosclerotic angiopathy showed that those with abnormal findings were definitely more numerous in the disturbance of glucose tolerance group.
