Diversity Analysis Of Bacteria And Archaea Of Deep-sea Hydrothermal Sediments In The East Pacific Ocean And Classification And Identification Of A Mesophilic Bacterium

Deep-sea hydrothermal vent is an extreme ecosystem which hashigh-temperature, high pressure and a lot of reducing substances. This kind ofecosystem is similar to the environment on earth where the early life lived. There area variety of microbes (especially thermophiles) which have unique physiologicalmetabolic types inhabiting deep-sea hydrothermal vent. Therefore, microbial diversityanalysis of deep-sea hydrothermal vent provides important basis for the study of theorigin of life, the exploitation of deep-sea microbial resources and obtaining valuablegenetic resources. Based on abundant microbial resources and their potentialapplication value, on the following three aspects of works were carried out in thispaper:Part1: Bacterial and archaeal diversity of deep-sea hydrothermal sediments fromS14-TVG10and S16-TVG12sites in the East Pacific Ocean were investigated bypolymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)analysis in this paper, the main results were as follows:Bacterial diversity was abundant and there were a lot of novel bacterial groups indeep-sea hydrothermal sediments in the East Pacific Ocean. Dominant groups ofbacteria were Delta-Proteobacteria(11.73%), Planctomycetes (8.94%), Chloroflexi(8.94%), Candidate division JS1bacterium (8.94%), Gamma-Proteobacteria (7.82%),Epsilon-Proteobacteria (6.15%), Alpha-Proteobacteria (5.59%) and unclassifiedbacteria (21.79%). In addition, the study found that bacteria of S14-TVG10andS16-TVG12sites displayed different dominant groups. Most bacterial clonesbelonged to Gamma-Proteobacteria (15%), Planctomycetes (13.75%),Delta-Proteobacteria (12.5%) and Alpha-Proteobacteria (11.25%) in S14-TVG10site.However, Candidate division JS1bacterium (16.16%), Chloroflexi (12.12%) andDelta-Proteobacteria (11.11%) occupied favorable positions in S16-TVG12site.Archaea was abundant and there were a lot of novel archaeal groups in deep-sea hydrothermal sediments from two sites in the East Pacific Ocean, and the distinctcommunity structure and diversity of archaea in deep-sea hydrothermal sedimentssuggested that the sampling area was influenced by hydrothermalism. Phylogeneticanalyses revealed that a total of199random16S rRNA gene clones were assigned toThaumarchaeota (46.73%), Euryarchaeota (42.71%), Crenarchaeota (9.55%) andunclassified archaea (1%). Among them, a genus Nitrosopumilus belonging to thephylum Thaumarchaeota and a class Thermoplasmata belonging to the phylumEuryarchaeota were the dominant groups, representing38.19%and37.69%ofarchaeal clones, respectively. One hundred and three archaeal clones fromS14-TVG10site belonged to Thaumarchaeota（84.47%）and Euryarchaeota (15.53%).Ninety six archaeal clones from S16-TVG12site were assigned to Euryarchaeota(71.88%), Crenarchaeota (19.79%), Thaumarchaeota (6.25%) and unclassifiedarchaea (2.08%).Part2: In this paper, forty eight strains were isolated and purified with ten kindsof media from deep-sea hydrothermal sediments of S009-TVG005, S024-TVG18,S025-TVG19and S18-TVG12sites in the the East Pacific Ocean. They wereaffiliated with six phylum (Gamma-Proteobacteria, Alpha-Proteobacteria,Actinobacteria, Firmicutes, Deinococcus-Thermus and Euryarchaeota) and twentyfour genera (Alteromonas, Arthrobacter, Aurantimonas, Bacillus, Dietzia,Erythrobacter, Geobacillus, Halomonas, Idiomarina, Kocuria, Loktanella,Marinobacter, Microbacterium, Nocardioides, Novosphingobium, Pseudomonas,Psychrobacter, Salinibacterium, Sulfitobacter, Thalassospira, Thermus,Thermococcus, Palaeococcus and one unidentified genus). Strain LQ1exhibited16SrRNA gene sequence similarity value of92.86%to the closest related recognizedspecies Aestuariibacter salexigens JC2042T, so strain LQ1was likely to represent anovel species within a new genus.Part3: In this paper, we presented the taxonomic characterization of strain LQ1with polyphasic taxonomy. Strain LQ1was an aerobic, gram-negative bacterium. Cells were rod-shaped,0.6~0.8μm in width and1.7~1.9μm in length with a polarflagellum. Growth occurred at10~40℃(optimal temperature35℃), at pH6.0~10.0(optimal pH7.0~8.0) and in the presence of0.5~14%(w/v) NaCl (optimal NaCl%2~3%). The major fatty acids of strain LQ1were C17:010-methyl, C16:0, SummedFeature3(C16:1ω7c/ω6c), Summed Feature8(C18:1ω7c/ω6c) and C16:0N-alcohol.The major polar lipids of strain LQ1contained phosphatidylethanolamine (PE),phosphatidylglycerol (PG), three unknown glycolipids (GL), three unknownphospholipids (PL) and an unknown polar lipid (P). The predominant isoprenoidquinone of strain LQ1was Q-8and the DNA G+C content was51.1mol%. Theisolate exhibited heterogeneity in16S rRNA gene sequences and low16S rRNA genesequence similarities (<93.3%) with the closest related species of genera within thefamily Alteromonadaceae. On the basis of chemotaxonomic and phylogenetic analysis,strain LQ1represented a novel species within a new genus, for which the nameMarisediminibacter pacifica gen. nov., sp. nov. is proposed.