Stratified active archaeal communities in the sediments of Jiulong River estuary, China

Qianqian Li,Xiang Xiao,Zhiwei Chen,Xijie Yin,Fengping Wang

doi:10.3389/fmicb.2012.00311

Abstract

Here the composition of total and active archaeal communities in a sediment core of Jiulong River estuary at Fujian Province, Southern China was reported. Profiles of CH4 and SO2−4 concentrations from the sediment core indicated the existence of a sulfate-methane transition zone (SMTZ) in which sulfate reduction-coupled anaerobic oxidation of methane (AOM) occurs. Accordingly, three sediment layers (16–18.5 cm, 71–73.5 cm, and 161–163.5 cm) from the 1.2 m sediment core were sectioned and named top, middle and bottom, respectively. Total DNA and RNA of each layer were extracted and used for clone libraries and sequence analysis of 16S rRNA genes, the reverse transcription (RT)-PCR products of 16S rRNA and methyl CoM reductase alpha subunit (mcrA) genes. Phylogenetic analysis indicated that archaeal communities of the three layers were dominated by the Miscellaneous Crenarchaeotal Group (MCG) whose ecological functions were still unknown. The MCG could be further divided into seven subgroups, named MCG-A, B, C, D, E, F, and G. MCG-A and MCG-G were the most active groups in the estuarine sediments. Known anaerobic methanotrophic archaea (ANMEs) were only found as minor components in these estuarine archaeal communities. This study, together with the studies of deep subsurface sediments, would be a very good start point to target and compare the specific active archaeal groups and their roles in the dark, deep subsurface sediment environments.

Highlights

Marine subsurface sediments probably constitute one of the largest reservoirs of biomass on Earth (Whitman et al, 1998)
Most the methane in marine sediments is oxidized before reaching the aerobic waters column and the atmosphere by anaerobic oxidation of methane (AOM) coupled to sulfate reduction catalyzed by microbes in the marine sediments
In sulfatemethane transition zone (SMTZ) from some deep marine subsurface sediments, such as from Peru Margin sites, ANMEs were not detected, but other uncultivated archaeal groups including South African Gold Mine Euryarchaeotic Group (SAGMEG), Miscellaneous Crenarchaeotal Group (MCG) and Marine Benthic Group B (MBGB) were found as main components (Inagaki et al, 2006)

Summary

Introduction

Marine subsurface sediments probably constitute one of the largest reservoirs of biomass on Earth (Whitman et al, 1998). The diversity of prokaryotic communities in various marine sediments has been studied extensively, but most microbial phylotypes belong to uncultivated groups of unknown physiology and ecological functions (Sørensen and Teske, 2006) Uncultivated archaea, such as Marine Group I (MG-I), Marine Group II (MG-II), Miscellaneous Crenarchaeotic Group (MCG), Marine Benthic Group B (MBGB), Marine Benthic Group D (MBGD) were found as dominant groups at some deep-sea sediments, but were widespread in various environments in nature. These groups were suggested to play important roles in the global cycling of carbon and nitrogen (Orphan et al, 2001; Teske and Sørensen, 2008). In a sediment core from Peru Margin site 1227 (Ocean Drilling Program Leg 201), members of MCG and MBGB archaea were found to be more active in the SMTZ than in sediment layers above and below, suggesting either direct or indirect involvement of these archaea in AOM (Sørensen and Teske, 2006)

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Conclusion