|Place of Conferral||北京|
|Keyword||渤海 入海河流 沉积物 铁还原菌 产甲烷菌 Bohai Sea Surrounding River Sediments Iron Reducing Bacteria Methanogens|
1、通过对滨海河流沉积物中电活性铁还原微生物的研究，结果发现界河沉积物Jh2、Jh3样品具有明显的铁还原活性；克隆文库表明两个位点具有特征性的铁还原细菌群落结构，Jh2样品中铁还原菌主要以Geobacter sp.为主；而Jh3样品中铁还原菌主要以Clostridium sp.为主；并在滨海河流沉积物中，分离得到了一株具有电活性的铁还原菌（JhA）。以上结果拓展了对于Anaerosinus sp.这一新菌种电活性的认识；同时，环境中新分离得到具有电活性的铁还原微生物，将为重金属环境修复提供菌株来源，具有潜在的应用价值。
Methane is an important greenhouse gas, which is produced by methanogens, and the coastal area sediments are important potential sources. In conventional opinion, the iron oxides can compete with methanogens for electrons and thereby inhibiting methane production. Our previous research has showed that it would be different for iron-reducing bacteria with the ability of extracellular electron transfer. Therefore, how to reveal the diversity of iron-reducing bacteria with electronchemical activity and methanogens with different metabolic pathways in this region, as well the effect of iron oxide transformation processes on the methanogenesis, which are of crucial scientific significance for assessing the greenhouse gas emissions in the river-sea interaction region and elucidating the biogeochemical carbon and iron coupling cycle. In this study, the sediments from the Bohai Sea and its inlets to the sea were studied. Firstly, the diversity of iron-reducing bacteria in different regions of the coastal river was analyzed and a new iron-reducing bacterium with electroactivity was isolated. Secondly, the iron oxides transformation under anaerobic methanogenesis condition was revealed. Lastly, the spatial distribution of methanogens in sediments of different sections in Bohai Sea, with the diversity and production of methanogens under different gradients, including spatial and salinity, across river to sea were analyzed. The main conclusions obtained are as follows:
With the study of electrochemically active iron (III)-reducing bacteria in coastal riverine sediments, the results showed that the Jh2 and Jh3 samples of the JieHe river sediments had iron reducibility. And the clone library showed that the two sediments had the characteristics of the iron reducing bacteria community structure. The iron reducing bacteria in the Jh2 samples were mainly dominated by Geobacter sp., while the Jh3 samples was Clostridium sp. And the electroactivity bacteria (JhA) was isolated from coastal river sediments. These results expand the understanding of the electrical activity of the new strain of Anaerosinus sp. At the same time, the electroactive isolates from the environment will provide the source of strain for the bioremediation of heavy metal environment with important application value.
With the study of the production and transformation of magnetite in the methanogenic consortia from coastal riverine sediments, it has been found that iron-reducing bacterial and methanogens were contained in it. In the presence of amorphous iron(III) oxides, the iron-reducing bacteria would reduce the ferric iron that compete the electrons with methanogens, thereby inhibiting the methan production. But with the conversion of amorphous iron to magnetite, the extracellular electron transfer occurred mediated by magnetite, so the methane production was promoted. Beyond our consideration, the magnetite itself could also act as an electron acceptor. As a result, the magnetite was reduced by iron-reducing bacteria with competing electrons and inhibiting methane production. These results revealed that the effect of magnetite production and conversion in methanogens consortia on the electron flow between iron-reducing bacteriaand methanogens.
Studies on microbial community diversity and methanogenic potential in sediments from different areas of the Bohai Sea showed that there were similar main microbial T-RFs in the in situ samples with spatially different. Total iron extracted from sediments has significant effects on bacterial community structures, but not for archaeal community. Desulfovibrio and Thiobacillus were the dominanted bacteria in the sample, and Methanobacterium and Methanosarcina were the main dominanted archaea. The methane production of regional sediment samples varies in the enrichment process, showing a higher methane yield in near-shore samples. It is speculated that bacteria in the sediments of the Bohai Sea, especially those related to the iron cycle, might be an important factor affecting the potential for methanogenesis. It was deserved to mention that human activities might increase the potential for methane emission in the offshore regions.
In order to explore more detail information about the changes of methanogens across Yellow River to Bohai Sea gradient, it has been found that the diversity of methanogens in the sediments varied from multi-trophic communities to specific methylotrophic communities. Methylotrophic methanogens were in both in situ sediments. Methanococcoides was the main methanogens in the Bohai Sea, while that of the Yellow River samples were dominated by Methanosarcina. After seawater enrichment culture, it was revealed that active Methanococcoides dominated in the BS enrichment cultures with trimethylamine as the substrate, methylotrophic Methanolobus dominated in the YR enrichment cultures, which was limitedly detected in in situ sediment samples. Methanosarcina were also detected in this gradient samples as well. These results indicated that the methanogens in Bohai Sea were not mainly from the Yellow River. The same species of Methanosarcina mazei were isolated from the area across a river to sea by the culture-dependent method, which were wide distributed. Our results showed the distribution of diverse methanogens across a river to sea gradient may shed light on adaption strategies and survival mechanisms of methanogens.
|MOST Discipline Catalogue||理学 ; 理学::海洋科学 ; 理学::生物学|
|王炳臣. 渤海及其入海河流沉积物中铁还原菌电活性及产甲烷菌多样性的研究[D]. 北京. 中国科学院研究生院,2019.|
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