Molecular phylogenetic and chemical analyses of the microbial mats in deep-sea cold seep sediments at the northeastern Japan Sea

Abstract

Microbial communities inhabiting deep-sea cold seep sediments at the northeastern Japan Sea were characterized by molecular phylogenetic and chemical analyses. White patchy microbial mats were observed along the fault offshore the Hokkaido Island and sediment samples were collected from two stations at the southern foot of the Shiribeshi seamount (M1 site at a depth of 2,961 m on the active fault) and off the Motta Cape site (M2 site at a depth of 3,064 m off the active fault). The phylogenetic and terminal-restriction fragment polymorphism analyses of PCR-amplified 16S rRNA genes revealed that microbial community structures were different between two sampling stations. The members of ANME-2 archaea and diverse bacterial components including sulfate reducers within Deltaproteobacteria were detected from M1 site, indicating the occurrence of biologically mediated anaerobic oxidation of methane, while microbial community at M2 site was predominantly composed of members of Marine Crenarchaeota group I, sulfate reducers of Deltaproteobacteria, and sulfur oxidizers of Epsilonproteobacteria. Chemical analyses of seawater above microbial mats suggested that concentrations of sulfate and methane at M1 site were largely decreased relative to those at M2 site and carbon isotopic composition of methane at M1 site shifted heavier ((13)C-enriched), the results of which are consistent with molecular analyses. These results suggest that the mat microbial communities in deep-sea cold seep sediments at the northeastern Japan Sea are significantly responsible for sulfur and carbon circulations and the geological activity associated with plate movements serves unique microbial habitats in deep-sea environments.

Dominant bacterioplankton populations in the meromictic Lake Suigetsu as determined by denaturing gradient gel electrophoresis of 16S rRNA gene fragments

“…In general, the DGGE bands related to the Bacteroidetes were detected from all sampling depths and dates. All of these sequences were closely related to 16S rDNA from uncultured bacterium in environmental samples including one from limnic and marine environments, and the terrestrial environment (Arakawa et al 2006;Crump et al 2007;Hansen et al 2007;Macbeth et al 2004;Pernthaler et al 2004;Riemann et al 2008;Skidmore et al 2005). Populations possessing a fermentative metabolism exist in Bacteroidetes (Reichenbach 1992;Saha 1992), suggesting they may degrade organic matter in the anaerobic environments of Lake Suigetsu in the euphotic and chemocline waters.…”

Microbial diversity and activity in hypersaline high Arctic spring channels

“…In similar investigations of gradients along marine methane seeps, differences in geochemical conditions have been shown to correlate with niches occupied by distinct microbial communities including different spatial abundance of ANME archaea (Arakawa et al 2006;Knittel et al 2005) and simple assemblages of key functional groups including methanotrophs, hydrocarbon degraders, sulfatereducers and sulfide-oxidizers (Jørgensen and Boetius 2007;Valentine 2002;Valentine and Reeburgh 2000). The presence of numerous species in the LH channel environment not found in the LH source reflects a greater potential metabolic diversity utilizing a variety of nitrogen and sulfur substrates in addition to methane.…”

Distribution of Cold-Adapted Ammonia-Oxidizing Microorganisms in the Deep-Ocean of the Northeastern Japan Sea

“…Sediment samples were collected from site M1 (43°20'N, 139°39'E), described previously by Arakawa et al 2) , at the southern foot of the Shiribeshi seamount by using MBARI cores deployed on the Shinkai 6500 (dive no. 6K960).…”

“…The smell of hydrogen sulfide was detected in black sediment CBK. It is presumed that the amount of molecular oxygen is decreased in black sediment CBK compared to the layers above, because remarkable anaerobic oxidation of methane occurred with the detection of sulfate-reducing bacteria belonging to Deltaproteobacteria in black sediment 2) .…”