Isolation And Characterization Of A Deep-Sea Piezophile Paroceanicella Profunda D4M1~T And Determining The Mechanisms Of Bacterial Adaptation To Hydrostatic Pressure

The deep-sea environment accounts for about three-quarters of the volume of the entire ocean,yet the study of this massive integrated living system is still in its infancy.Various environmental variables,such as darkness,high salinity,low temperature,and the varied high hydrostatic pressure with depth that form a unique ecosystem and abundant marine species.The ocean has an average depth of 3800 m,and hydrostatic pressure,as one of the key environmental variables,affects the survival and evolution of deep-sea organisms.Facing this extreme environmental condition,marine microorganisms have evolved special adaptation strategies.However,such mechanisms remain largely unknown.In recent years,with the development of sequencing technology,comparative genomics,proteomics and other omics methods and technologies,scientists can quickly obtain relevant omics data to explore and study the evolution,biochemistry,physiology and diversity of marine microorganisms.In this project,a novel piezophilic alphaproteobacterium,Paroceanicella profunda,strain D4M1^T,was isolated from a deep seawater sample of the Mariana Trench at the depth of 10890 m.Phenotypical,physiological,biochemical,and chemotaxonomical analyses of this strain were carried out with multiphase taxonomy and modern molecular biology technology to establish the taxonomic status of the bacterium.Cells were Gram-stain-negative,aerobic short rods,and grew optimally at 37°C,p H 6.5 and 3.0%?w/v?Na Cl.Strain D4M1^T was piezophilic with the optimum pressure of 10 MPa.The principal fatty acids were C_18:1?7c/C_18:1?6c and C_16:0 Major respiratory quinone was ubiquinone-10,and predominant polar lipids were phosphatidylglycerol,phosphatidylethanolamine,and an unidentified aminophospholipid.16S r RNA gene analysis showed that strain D4M1^T was most closely related to Oceanicella actignis PRQ-67^T?94.2%?and Oceanibium sediminis O448^T?94.2%?.Phylogenetic analyses based on both 16S r RNA gene and genome sequences showed that strain D4M1^T formed an independent monophyletic branch paralleled with the genus Oceanicella in the family Rhodobacteraceae.The combined evidence shows that strain D4M1^T represents a novel species of a novel genus in the family Rhodobacteraceae,for which the name Paroceanicella profunda gen.nov.,sp.nov.is proposed?type strain D4M1^T=MCCC1K03820^T=KCTC 72285^T?.This study further sequenced the whole genome of strain D4M1^T,focusing on the analysis of the genes involved in maintaining cell membrane fluidity and physiological functions,promoting energy production and promoter transcription in the process of high-pressure adaptation,and.it's the mechanisms of hydrostatic pressure adaptation.The whole genome of strain D4M1^T contained a circular chromosome and six plasmids,with a total of 5,468,583 bp,and the G+C content was 70.2 mol%.The genome encodes 4942predicted genes,including 4855 protein-coding genes,78 r RNAs.Complete genome analysis revealed that there were 4057 genes?82.1%?assigned to 24 different clusters of orthologous groups.Genomic analysis showed that strain D4M1^T contains at least 156genes related to high pressure adaptation,including those for unsaturated fatty acid synthesis,chaperone proteins,respiratory chain,pressure regulator,transporter,heat shock protein and cold shock proteins.Genomic analysis revealed abundant clues on bacterial high-pressure adaptation and piezophilic lifestyle of strain D4M1^T.