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Archaea plays an important role in the global geobiochemical circulation of various environments. However, much less is known about the ecological role of archaea in freshwater lake sediments. Thus, investigating the structure and diversity of archaea community is vital to understand the metabolic processes in freshwater lake ecosystems. In this study, sediment physicochemical properties were combined with the results from 16S rRNA clone library-sequencing to examine the sediment archaea diversity and the environmental factors driving the sediment archaea community structures.

Seven sites were chosen from Poyang Lake, including two sites from the main lake body and five sites from the inflow river estuaries. Our results revealed high diverse archaea community in the sediment of Poyang Lake, including Bathyarchaeota This study provides primary profile of sediment archaea distribution in freshwater lakes and helps to deepen our understanding of lake sediment microbes. As the third domain of life, archaea was once considered as significant habitant of extreme environments, but increasing evidence reveals their widespread presence in various nonextreme environments, including soil, ocean, and freshwaters [ 1 ].

Archaea is found having an important role in global biogeochemical processes, such as methanogenesis and methane oxidation [ 2 ], sulphate reduction [ 3 ], and ammonia oxidation [ 45 ].

In freshwater environments, active archaea community is responsible for methane release and nitrogen transformation, especially in benthonic water and sediments [ 6 ]. Consequently, the investigating of sediment archaea community is vital to understand the metabolic processes in freshwater lake ecosystems [ 8 ]. Lake sediment is an active place with a high abundance of microorganisms, which is subjected to the changes of organic matter degradation, resuspension, and redeposition of various chemicals [ 9 ].

Compared to bacteria, the diversity and community distribution of sediment archaea have received much less attention in freshwater lake environments. Few previous studies indicated the variation of archaea community structure and diversity with several factors, such as sediment depth, sampling sites, and contamination [ 10 — 12 ]. Archaea community is less influenced by environmental factors compared with bacteria [ 13 ]; several parameters are found to affect the distribution of archaea in lake sediments.

The salinity played an important role in controlling diversity and distribution of archaea in estuarine sediments [ 1415 ], particle sizes and water O 2 saturation also shaped the sediment archaea distribution [ 16 ].

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However, subject to the poor culturability and limited isolates of archaea members, the taxonomy was obscured in many previous studies. The conventional affiliation of some archaea groups was named after their environmental characteristics or finding orders and often scattered several different phylogenetic taxa identified by molecular evolution methods.

Moreover, investigation on archaea communities in sediments from a number of lakes has not been concerned, and fewer studies have been carried out to elucidate the spatial distribution and environmental impact of sediment archaea communities. As one of the largest freshwater reservoirs of China, Poyang Lake plays a vital role in the regional climate regulation, ecological keeping, and economic development.

However, the 715-1 conditions of Poyang Lake changed dramatically in recent years, and the overall water areas also decreased. Meanwhile, the eutrophication and pollution bhi by agriculture, aquiculture, and industrial activities threatened the water safety [ 17 — 19 ]. The inflow river has made an important contribution to the eutrophication and contamination of Poyang Lake; among the five tributaries, Gan, Xin, and Rao Bggi were polluted by industrial plants discharges copper bbi phosphate mines in the upstream of Rao and Xin Rivers and urban wastes Nanchang City in the upstream of Gan River [ 20 ].

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Many studies have been conducted to ngi the hydrological regime, water quality and biodiversity of fishes, birds, plants, and bacterioplankton communities of Poyang Lake [ 21 — 25 ]. The distribution of archaea community and its ecological role is not well concerned in Poyang Lake. The objective of the present study is to characterize the archaea community structure in sediments of Poyang Lake and estimate the influence of surface sediment properties on 71-1 spatial distribution of archaea community.

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This study was the primary attempt byi unscramble the total archaea community in the Poyang Lake sediment. Both central lake and tributary estuaries are included in this study. Although the water area of Poyang Lake is very huge, two parts could be divided depending on the hydrographic conditions. The north part is a water channel with deep and quick current, while the south part has vast water area and slow current.

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Seven sampling sites were selected for study Figure 1: The coordinates and water depth of these selected sampling sites are shown in Table 1. N means the ratio of 7511- organic carbon to nitrogen. Three samples were collected at each site under aseptic conditions and put on ice in a container and transported to the lab immediately.

For each site, three samples were mixed together for homogenization. Afterwards, samples were divided into two halves.

Sediment samples bti timely freeze-dried to detect geochemical characteristics. Total organic carbon TOCtotal nitrogen TNand total phosphorus TP contents were, respectively, analyzed by the Walkley-Black wet oxidation procedure, the micro-Kjeldahl method, and the phosphomolybdic acid blue color method [ 26 ].

The concentrations of heavy metals including copper Cuzinc Znlead Pband cadmium Cd were quantified by microwave digestion bgj. Genomic DNA was extracted from 0. The obtained raw sequences were analyzed using Bellerophon http: Then, the representative sequences were queried using Blast program http: The most similar sequences were extracted from the GeneBank database.

The phylogenetic neighbor-joining tree, including the obtained sequences and their closest relatives, were constructed using the MEGA software 5. To investigate relationships between sediment archaea community and environmental variables, redundancy analysis RDA with Monte Carlo tests was carried out using the Canoco program for Windows 5.

A heatmap was produced in R project R Furthermore, Pearson coefficient correlations between the major archaea taxa, diverse indices, and sediment variables were calculated using SPSS The physicochemical properties of sediment samples from Poyang Lake were heterogeneous among sites.

P were similar among sites Table 1. Compared with the regional background values of Poyang Lake [ 30 ], higher contents of four metals were revealed by this study. The content of Zn from all seven sites remarkably exceeded the background value, and Pb content from most sites also exceeded the background value except for sites NP and GJ.

These results suggested potential metal pollution in the region of Poyang Lake. The metal contents of Zn, Cd, Cu, and Pb among different sites. The dotted lines stand for the environmental background values of Poyang Lake. In this study, seven clone libraries of archaea 16S rRNA gene from sediments of Poyang Lake were constructed and characterized. The OTU numbers of each clone library varied from 13 to 56, and positive clones varied from 23 to Shannon and Simpson index showed high archaea diversity in all samples, except for Site 1 Table 2.

However, both dominance and evenness showed diverse and stable structures of archaea community from sediment samples. The seven phyla included Bathyarchaeota The Unclassified Archaea still represented 3.

Some previously described groups were included, such as MCG group 5b, group 8, group 4, group 11, group 5a, and group 15 Figure 3. The phylum Euryarchaeota could be deeply divided into six orders, Methanomicrobiales Numbers in parentheses indicate the number of sequences affiliated to the branches a detailed phylogenetic tree was available in supporting materials in Supplementary Material available online at http: The main composition of the whole archaeal community was also shown in the pie chart.

The sediment archaea community showed diverse distribution patterns among seven sampling sites. Based on the heatmap analysis of archaea community on order level affiliation, all sampling sites could be divided into three groups: The heatmap profile showing the sediment archaea community compositions from seven sampling sites of Poyang Lake.

With an experiment-wise error rate of 7511-1. For sites NP and SP from the central lake, the most abundant archaea both belonged to 571-1 Gbi correlation coefficients were used to investigate the correlations between the lake sediment bfi and the archaea communities Table bhi.

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However, only a few data dramatically correlated with others. The ACE values of archaea community showed remarkable negative correlations to the ratio of C: The confined influence was confirmed by bgu RDA results, although the physicochemical factors in the first two RDA axes, respectively, explained Aquatic sediments are important sites for matter transformation and energy metabolisms.

Therefore, information on the microbial community composition bti of vital importance for better understanding of the metabolic processes in aquatic 7511. Up to now, the archaea community found in freshwater lake sediments 71-1 not so diverse as bacterial community. Phylogenetic analysis of the sediment archaea 16S rRNA gene libraries revealed high diversity in Poyang Lake, and the majority of archaea community belonged to common groups of river and lake sediments.

Similar to previous reports, the most frequently found archaea bhi this study was composed of Bathyarchaeota MCGThaumarchaeota, Methanosarcinales, Methanomicrobiales, Methanobacteriales, and Thermoplasmatales [ 31 ].

The sediment archaea community from 13 plateau freshwater lakes comprised 16 classified phyla and classes; MCG and Thermoplasmata were the most predominant 7511 [ 13 ].

In sediments of Lake Kivu and Lake Bled, Methanobacteriales, Methanosarcinales, and Thermoplasmata all played a big part in the whole archaea community; Crenarchaeota and Thaumarchaeota collectively take a small proportion compared with Euryarchaeota [ 3334 ]. Our study revealed spatial heterogeneity of archaea community in the sediment of Poyang Lake. Bathyarchaeota MCG comprised a large number of phylotypes from anoxic environments and can be divided up to 17 subgroups [ 35 ]. The broad range of habitats was an obvious feature for Bathyarchaeota members, and this point may be the reason for their dominating in many environments.

Bathyarchaeota was believed to have an organic heterotrophic lifestyle and can degrade buried organic carbon and detrital proteins in subsurface sediments [ 3637 ]. Bathyarchaeota was also found having methyl-coenzyme M reductase MCR complex and involved in methane metabolism recently and was the only group outside the phylum Euryarchaeota for methane metabolism [ 38 ].

As the most presently proposed phyla, Aigarchaeota and suspended Lokiarchaeota may both be involved in anaerobic carbon cycling [ 39 ]. Pacearchaeota and Woesearchaeota were previously reported from bgj sediments, but in surface waters of some lakes they were also detected [ 40 ]. The archaea community of NP and SP both from central lakes showed similar structures; the most abundant clones belonged to Methanosarcinales and Methanomicrobiales of Euryarchaeota.

Methanosarcinales and Methanomicrobiales were the most abundant Euryarchaeota groups in freshwater sediments, and both methanogenic and methanotrophic phylotypes ANME-2a, 2b were included [ 15 ]. The dominance of Methanomicrobiales and Methanosarcinales in sedimental archaea community of this study was not a single event, and similar results have also been reported in other freshwater lakes, such as Lake Biwa [ 41 ], Lake Soyang [ 42 ], and Lake Dagow [ 43 ].

Methanosarcinales and Methanomicrobiales usually draw energy from anaerobic oxidation of methane AOM and are coupled with bacterial sulphate reduction [ 44 ]. Thus, the proportion of these orders often increased with the necessary sulphate and 7751-1 carbon availability [ 4546 ]. This point was also validated in this study where the abundance of Hgi was positively correlated with TOC content. Thus, the abundance of Methanosarcina, Methanobacteriales, and Methanomicrobiales in this study may suggest that their growth substrate was not limited, and the elevation of organic carbon from eutrophication or terrestrial organic carbon influx may change methanogen abundance as well as CH 4 production rates [ 48 ].

MCG-1, Methanomicrobiales, and Methanosarcinales all have a wide habitat in various water environments. Thermoplasmatales was often related to methanogenic activities [ 4950 ] and was timely found in freshwater lake sediment [ 3351 ]. Thermoplasmatales has a notable proportion 7511-1 the Poyang Lake sediment of this study, which 7551-1 emphasis the active methanogenesis. The new genome reading byi Thermoplasmatales cells has revealed the genes that encode extracellular protein-degrading enzymes and which could enable them to survive on sedimentary detrital proteins [ 37 ].

Other reports suggested that some members of the Thermoplasmatales may represent a new order of methanogens that can utilize methylamine [ 52751–1 ].