Metagenomic Study Of The Structure,Evolution And Metabolic Potential Of Microbial Communities Inhabiting Deep Sea Hydrothermal Chimneys

Chemoautotrophic microbial communities inhabit around the deep sea hydrothermal chimneys.As the primary producer,they are not only the basic for the existence of the whole hydrothermal ecosystem,but also play an important role in the global geochemical cycling of carbon,sulfur and nitrogen.Furthermore,the geothermal environments of deep sea hydrothermal vents are analogous to those of early Earth,and the extremophiles are ideal objects for us to study the origin and evolution of life.Due to the limitation of sampling and methodology,our knowledge about the taxonomic structure of deep sea hydrothermal microbial communities and the phylogenetic and metabolic features of those uncultured microbes still largely blank.In this study,we analyzed two microbial communities from two deep sea hydrothermal chimneys with distinct activities based on metagenomics.Both of two chimney were sampled from the hydrothermal vents of East Pacific Rise 9 °N ocean middle ridge,the chimney from Lvent was erupting hot fluid and the other one from M-vent was at inactive stage.The taxonomic results based on reconstructed full-length 16 S r RNA genes indicate Epsilonbacteraeota and Aquficae are the dominated group in the active L-vent microbial communities,whereas the microbial diversity is higher relatively for the microbial communities from inactive M-vent chimney including Gamma-,Delta-,Alphaproteobacteria,Nitrospira and Bacteroidetes.Besides,we also reconstructed 4 and 2 high quality genomes of Epsilonbacteraeota and Thermotogae EM3 group respectively.In particular,these uncultured Epsilonbacteraeota taxa have metabolic potentials of sulfur and hydrogen oxidation as well as the large biopolymers transporters and secretion system.Solid phylogenetic evidences support that EM3 group is totally independent with the others taxa of Thermotogae as a bacterial phylum level taxon.Genomic annotation indicate that EM3 group is a kind of heterotrophic bacteria could degrade the extracellular carbohydrates and proteins potentially,besides they also have powerful metabolic potentials of glycosyl Transferases involved biofilm formation and bacterial secretion system.In summary,this study clearly deciphered the compositional structure of microbial communities from two deep sea hydrothermal chimneys with distinct activities,reconstructed and analyzed genomes of dominating uncultured Epsilonbacteraeota,demonstrated the previous Thermotogae EM3 group is belong to a independent bacterial phylum level taxon and reconstruct their metabolic pathway and feature.Therefore,our work not only help us to further understand the structure succession of hydrothermal microbial communities with the geothermal activity,but also suggests that uncultured deep sea hydrothermal microbial communities could play an important role in the deep sea geochemical elements cycling.Furthermore,it also could gain our insight into the life in deep biosphere as well as the origin and evolution of life.