Diversity Of Culturable Bacteria In The Deep-sea Of The South Pacific Gyre And Taxonomic Analysis Of Two Novel Bacteria

The deep sea is a extreme ecological environment with permanently cold(excluding hydrothermal vent), high-pressure and dark, where microorganisms haveto adapt to this specific habitat in terms of morphology, physiology and metabolisms.They are ideal source of extreme microorganisms, and have a broad prospects fordevelopment. The study of microbial community structure is the basis of its overallfunctionality, and it is the key issue of microbial ecology. South Pacific Gyre (SPG) islocated south of the equator, between South America and Australia. It is the largest ofthe ocean gyres and its center is farther from continents than the center of any othergyre. The sediment of this region has the lowest organic burial rates in the ocean. Therecent survey cruise demonstrates that shallow sediment of this region contains thelowest cell concentrations and lowest rates of microbial activity ever encountered inshallow marine sediment. However, the nature of life in the sediment beneathmid-ocean gyres is very poorly known. Because interstitial waters are oxic throughoutthe sediment column in most of this region, the sedimentary community of the SPG ispredominantly aerobic.In this study, sediments and bottom seawater samples were collected duringIODP (Intergrated Ocean Drilling Program)329, phylogenetic diversity of culturablebacteria from7sites of the SPG was studied, and six types of the extracellularenzymatic activities were detected on part of the strains from sediment. In addition,two novel marine bacteria were classified.To study the diversity of the culturable bacteria in deep sediment of the SPG,229bacterial strains were isolated from7sites and16S rDNA sequences were analyzed.The results showed that there were5phyla,50genera and95species, andActinobacteria was the dominant phylum in terms of quantity and species.Gram-positive bacteria (Actinobacteria and Firmicutes) accounted for70%. Therewere106strains belonged to Actinobacteria,60strains belonged to Firmicutes,16strains belonged to Alphaproteobacteria,4strains belonged to Betaproteobacteria,39 strains belonged to Gammaproteobacteria,3strains belonged to Bacteroidetes and1strain belonged to Yeast. There were8dominant genera such as Micrococcus, Bacillus,Vibrio, Microbacterium etc, and18dominant species such as Micrococcusyunnanensis, Micrococcus antarcticus, Staphylococcus cohnii etc.. In addition,10strains might be novel genera or species. The results of the extracellular enzymaticactivities showed that all the6types of the extracellular enzymes had been detected.At4C there were still many strains had the extracellular enzymatic activities. Thenumber of gelatinase-positive strains and amylase-positive strains were the largest.To study the diversity of the culturable bacteria in bottom seawater of the SPG,176bacterial strains were isolated from7sites and16S rDNA sequences wereanalyzed. The results showed that there were5phyla,31genera and79species, andGammaproteobacteria was the dominant phylum in terms of quantity and species.There were143strains belonged to Gammaproteobacteria,7strains belonged toAlphaproteobacteria,2strains belonged to Betaproteobacteria,11strains belonged toFirmicutes,6strains belonged to Actinobacteria,5strains belonged to Bacteroidetesand2strains belonged to Yeast. There were10dominant genera such asPseudoalteromonas, Alteromona, Vibrio, Halomonas, etc, and12dominant speciessuch as Pseudoalteromonas paragorgicola, Halomonas meridiana, Vibrio campbelliietc. In addition,9strains might be novel genera or species. Some undiscoveredbioactive substances, especially cold-adaptive enzymes, may exist in these strains andare worthy of further exploitation.Two novel Gram-stain-negative, aerobic strains (ZXM100Tand ZXM098) wereisolated from seawater in the coastal region of Qingdao, China, during a massivegreen algae bloom. Cells were ovoid to irregular short rods and lacked flagella.Poly-b-hydroxybutyrate was accumulated. Cells did not contain bacteriochlorophyll a.It grows within a NaCl concentration of3-9%and temperature range is22°C-28°C.C18:1v7c, C18:0and C16:0were the major fatty acid components. The polar lipids ofZXM100Twere phosphatidylglycerol, phosphatidylethanolamine,phosphatidylcholine, a single lipid and an unidentified aminolipid. The predominantisoprenoid quinone of ZXM100Twas Q-10. Phylogenetic analysis based on16SrDNA gene sequences showed that strains belonged to the family Rhodobacteraceae.Based on the results obtained in this study, strain ZXM100Twas considered torepresent a novel species in a new genus, for which the name Lentibacter algarum gen. nov., sp. nov. is proposed. The type strain is ZXM100T (=LMG24861T=CGMCC1.10234T); the DNA G+C content of the type strain is54.6mol%.A novel Gram-stain-negative, catalase-and oxidase-positive bacterium,designated strain H50T, was isolated from an amphioxus breeding zone in the coastalregion of the Yellow Sea, China. Cells were ovoid shaped, lacked flagella and werefound to contain bacteriochlorophyll a. Poly-b-hydroxybutyrate was accumulated.The temperature range for growth was0–37C. The major fatty acids were C18:1ω7cand C16:0. The predominant respiratory quinone was Q-10. The following polar lipidswere present: diphosphatidylglycerol, phosphatidylglycerol and an unknown lipid.DNA G+C contents was57.7mol%. Strain H50Texhibited the highest16S rDNAgene sequence similarity to Roseovarius mucosus DSM17069T(96.3%), Pelagicolalitoralis DSM18290T(96.3%) and Roseovarius tolerans DSM11457T(95.8%), andlower than95.7%to all the other related strains. In the phylogenetic trees, strain H50Twas clustered with the genus Roseovarius, but not Pelagicola. On the basis ofphenotypic, chemotaxonomic and genotypic data, strain H50Tis considered torepresent a novel species in the genus Roseovarius, for which the name Roseovariusovatus sp. nov. is proposed. The type strain is H50T(=CGMCC1.10799T=JCM17553T).