Isolation And Identification Of The Deep-sea Piezotolerant Bacteria And A Preliminary Study On The Pressure-resistant Mechanism Of A Shewanella Sp. Nov

The deep sea is an extreme environment which is dark,oligotrophic,high-pressure and low-temperature,in which piezotolerant bacteria live for a long time,forming different gene composition and physiological mechanism from atmospheric pressure microorganisms.The study of piezotolerant bacteria is helpful to explore the origin and evolution of life and other scientific issues,but the understanding of the pressure mechanism of these microorganisms is still very limited.In this paper,the deep-sea sediment samples were enriched and cultured,and the strain resources of piezotolerant microorganisms were isolated.The whole genome of a Shewanella sp.nov was analyzed,and the mechanism of pressure and cold resistance was preliminarily studied from the gene level.In this paper,the sediment samples collected from Yap trench were enriched and cultured under the condition of low temperature and high pressure,then 70 strains of piezotolerant bacteria were isolated and purified under normal pressure,belonging to14 genera including Pseudomonas.Based on the homology analysis of 16S rRNA gene sequence,it was found that the similarity between strain XXST-01~T and its most similar species Bacillus kyonggiensis NB22~T was 98.40%.It was found that XXST-01~T was rod-shaped,gram-positive,with endospores and flagella.Its growth range was 10-45?(optimal 37?),0-6%NaCl(optimal 0-0.5%,w/v),0.1-50 MPa(optimal 0.1 MPa).The genome size of strain XXST-01~T was 4.39 MB,G+C value was 38.2 mol%,and the results of ANI and DDH analysis of the related strains were 70.91-90.15%,19.80-40.50%,respectively.Based on the similarity of 16S rRNA and the difference of physiological and biochemical characteristics between XXST-01~T and the related strains,the strain was identified as a new species of Bacillus and named as Bacillus yapensis sp.nov.according to its isolation site.Shewanella sp.YLB-08~T was isolated from the deep-sea hydrothermal area.Experimental comparison found that the strain has stronger high-pressure adaptability than Baciillus yapensis XXST-01~T,and has the characteristics of psychrophilic and alkaliphilic,which is a typical extreme microorganism,so it was selected to carry out genome-wide analysis to explore its genes related to cold and pressure resistance.Complete genome sequencing and genome annotation display that the genome size was5785459 bp,and the G+C content was 43.52 mol%,containing 5256 protein coding genes,including a large number of genes related to respiratory chain,antioxidant/DNA repair,cold shock protein,transposase,with double flagella system,containing an unsaturated fatty acid synthesis pathway,making it adapt to the deep sea environment of high pressure and low temperature well.