| As one of the most important ecosystems on the earth,deep-sea is characterized of high pressure,aphotic,anaerobic and so on.In deep-sea,microorganisms occupy the largest biomass,in which the dominant communities are bacteria,archaea and viruses.With the progress of science and technology and the improvement of human understanding of deep-sea,human activities such as resource exploration and scientific investigation in deep-sea are increasing day by day,leading to a large number of deep-sea samples are brought to the land.When deep-sea samples enter the land,the first environment contacted may be the land soil with the physical and chemical properties similar to those of deep-sea.Deep-sea samples contain a large number of microorganisms and viruses.Once some of the deep-sea bacteria and viruses proliferate in terrestrial soil,the soil environment will be affected.However,little is known about the influence of deep-sea bacteria and viruses on the bacterial communities and functions of terrestrial soil.In this study,therefore,106 sediment samples from different habitat types of deep-sea were selected to characterize them.Firstly,the composition and the role of microorganisms were investigated.Then the formation of deep-sea biome was explored by simulating the process of deep-sea biome formation in situ.Based on these investigations,the effects of the bacteria and viruses from deep-sea on the bacterial communities and functions of terrestrial soil were explored.There are a lot of investigations on the diversity of deep-sea microorganisms.However,these studies focus on the seawater in deep-sea.The information about the diversities,distribution patterns and roles of microorganisms in deep-sea sediments at the large scale is limited.In this study,therefore,the bacteria and archaea were separately isolated from 106 deep-sea sediment samples of five typical deep-sea habitats,including hydrothermal vent,cold seep,seamount and mid-ocean ridge,from the Atlantic,Pacific and Indian Oceans and then subjected to 16 S r RNA gene sequencing.The results showed that the dominate bacterial phyla were Proteobacteria,Bacteroidetes,Firmicutes,Actinobacteria and Planctomycetes,and the dominat archaeal phyla were Thaumarchaeota,Euryarchaeota and Bathyarchaeota Marine Benthic Group E at the globe scale.The dominant microorganisms in different habitats were different.The dominant bacterial genera in hydrothermal vent,cold seep,hadal trench,seamount and mid-ocean ridge were Lactobacillus,Psychrobium,Halomonas,Alcanivorax and Lactobacillus,respectively and the dominant archaeal genus of all habitats was Marine Group I_Norank.It was found that the bacterial diversity in hydrothermal vent was the highest,while the archaeal diversity in cold seep was the highest.The core microorganisms,which existed in all habitats of deep-sea,included 481 bacterial genera and 16 archaeal genera.The deep-sea bacteria and archaea were involved in some special metabolic processes in deep-sea environment,including sulfur metabolism,nitrogen metabolism,methane metabolism and metal ion metabolism.The results also indicated that there were 42 pathogenic bacteria in deep-sea.Ninety-five sediment samples contained at least one pathogenic bacterium,which were distributed in the Atlantic,Pacific and Indian Oceans,showing that pathogenic bacteria were widely distributed in deep-sea.Our findings on the composition and distribution of deep-sea microorganisms and the distribution of pathogenic bacteria in deep-sea laid a foundation to further reveal the structures of microorganism communities in deep-sea.Deep-sea ecosystems,such as cold seeps and hydrothermal vents,have high biomass,even though they are located in the benthic zone,where no sunlight is present to provide energy for organism proliferation.Based on the co-existence of the reduced gases and chemoautotrophic microbes,it is inferred that the energy from the reduced gases supports the biocoenosis of deep-sea ecosystems.However,there is no direct evidence to support this deduction.Here,we developed and placed a biocoenosis generator,a device that continuously seeped methane,on the 1000-meter deep-sea floor of the South China Sea to artificially construct a deep-sea ecosystem biocoenosis.The results showed that microorganisms,including bacteria and archaea,appeared in the biocoenosis generator first,followed by jellyfish and Gammaridea arthropods,indicating that a biocoenosis had been successfully constructed in the deep-sea.Anaerobic methane-oxidizing archaea,which shared characteristics with the archaea of natural deep-sea cold seeps,acted as the first electron acceptors of the emitted methane;then,the energy in the electrons was transferred to downstream symbiotic archaea and bacteria and finally to animals.Nitrate reducing bacteria served as partners to complete anaerobic oxidation of methane(AOM)process.Further analysis revealed that viruses coexisted with these organisms during the origin of the deep-sea biocoenosis.Therefore,our study mimics a natural deep-sea ecosystem and provides the direct evidence to show that the chemical energy of reduced organic molecules,such as methane,supports the biocoenosis of deep-sea ecosystems.To evaluate the influence of deep-sea bacteria on the bacterial communities and functions of the terrestrial soil,the bacteria were respectively isolated from 106deep-sea sediment samples to treat soil,followed by the analyses of the bacterial communities and functions of soil.The results showed that the dominant genera of bacteria in soil were Ensifer,Nocardioides and Pseudomonas.Among 106 deep-sea sediments,the bacteria from 90 sediments did not significantly affect the bacterial communities of soil,while the bacteria from 16 sediments significantly changed the soil bacterial communities.The 16 sediments were DP027,DP029,DP047,DP059,DP060,DP063,DP078,DP082,DP083,DP087,DP093,DP095,DP096,DP102,DP104 and DP140.The bacteria that had the greatest influence on the structure of soil flora were from the sediment samples DP059 and DP029,which caused the changes of the abundances of 107 and 77 bacterial genera of the soil,respectively.The abundances of some deep-sea bacteria were zero in the terrestrial soil of the control groups,while the abundances of these bacteria were significantly increased in the soil of the experimental groups.These bacteria included Halomonas,Brevibacterium,Gemmobacter,Bacillus,Sulfitobacter,Erythrobacter,Aurantimonas,NS5 marine group,Psychrobacter,Gramella,Gillisia and Desulfobulbus,which might be a risk of alien invasion to the soil bacterial community.The results of the examinations of soil functions,including ammonium nitrogen content,iron reduction,sulfur conversion,urease activity,nitrate reductase activity,cellulase activity and manganese peroxidase activity,indicated that the bacteria from 17 deep-sea sediment samples,including DP027,DP029,DP 047,DP059,DP060,DP063,DP078,DP082,DP083,DP087,DP093,DP095,DP096,DP098,DP102,DP104 and DP140,resulted in significant inhibitions of the original functions of the soil.The data of comparative analyses revealed that the bacteria from 16 sediments,including DP027,DP029,DP047,DP059,DP060,DP063,DP078,DP082,DP083,DP087,DP093,DP095,DP096,DP102,DP104 and DP140,could significantly change the bacterial communities and functions of soil.These samples with biosafety risk came from the Atlantic,Pacific and Indian Oceans.In this study,two bacterial strains Halomonas titanicae and Bacillus meqaterium were isolated from deep-sea sediments.After the soil was treated with the deep-sea bacteria,the deep-sea bacteria could proliferate in the terrestrial soil to significantly cause the imbalance of the original functions of the soil.These findings indicated that the bacteria from some deep-sea sediments could proliferate numerously in the terrestrial soil to change the structure of soil bacterial communities,thus changing the soil functions.Based on the experiments in quantities,the results revealed that there existed the deep-sea bacteria to invade the terrestrial soil.Our findings provided the biosecurity data for the human deep-sea exploration and scientific expedition.To explore the influence of deep-sea virus on the bacterial community of soil and soil functions,the viruses isolated from 106 deep-sea sediments were used to treat the terrestrial soil,respectively,followed by the analyses of soil bacterial communities and soil functions.The analysis of diversity revealed that the deep-sea sediments had high viral diversities,of which the most abundant entity was bacteriophage.Among106 deep-sea sediments,the viruses from 96 sediments did not significantly affect the soil bacterial community,while the viruses from 10 sediments,including DP027,DP029,DP030,DP048,DP059,DP067,DP068,DP073,DP083 and DP123,could significantly change the soil bacterial community.The viruses from the sediment samples DP029,DP123 and DP059 had the greatest influence on the structure of soil flora,leading to the changes of the abundances of 109,97 and 84 bacterial genera,respectively.The results of the examinations of soil functions(ammonium nitrogen content,iron reduction,sulfur conversion,urease activity,nitrate reductase activity,cellulase activity and manganese peroxidase activity)showed that the viruses from 11deep-sea sediment samples,including DP027,DP029,DP046,DP047,DP048,DP059,DP067,DP068,DP073,DP083 and DP123 resulted in significant inhibitions of the original functions of the soil.The comparative analysis demonstrated that the viruses from 9 sediments(DP027,DP029,DP048,DP059,DP067,DP068,DP073,DP083 and DP123)could significantly change the bacterial communities and functions of soil,indicating that the viruses of the 9 deep-sea sediments affected soil functions by changing the structure of soil bacterial community.These sediment samples with biosafety risk were distributed in the Atlantic Ocean,the Pacific Ocean and the Indian Ocean.Based on the analyses of a large number of sediments in this study,it was found that the deep-sea viruses had a biosecurity risk to the terrestrial soil,which provided a biosafety support for human activities in the deep-sea. |
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