Phylogenetic studies on marine bacteria within the phylum Proteobacteria and Bacteroidetes

The oceans occupy 71% of earth's surface, with a volume of 1.46×109Km3 and average depth of 4,000m, and maximal depth of approximately 11,000m. The main problem in studying species distribution of on marine bacteria lies in the methods used to obtain viable cultures. Whether the isolates obtained by current culture methods represent indigenous population is unknown. Determining the representative physiological studies that can be performed on the vast numbers of marine bacteria that have yet to be cultured is still a matter of guesswork (Schute et al.,1993). Marine sponges are the most ancient multicellular animals, dating back to the Precambrian period, more than 635 million years ago. Their natural product diversity is among the highest found in nature. There is growing evidence that bacterial symbionts play a crucial role as producers of sponge-derived metabolites. In many sponge species, termed "high microbial abundance" (HMA) sponges, up to half the biomass can consist of microbial symbionts, whereas "low microbial abundance" (LMA) species, which live in the same habitats, contain much fewer symbionts. Often, distantly related HMA sponges from different oceans share remarkably similar microbial communities. In this study I attempted to elucidate the taxonomic position of nine novel marine bacterial strains that were isolated from marine seawater and marine sponges within the phylum Proteobacteria and Bacteroidetes by using polyphasic taxonomic approach. The phylogenetic trees based on the neighbour-joining (NJ), maximum-parsimony (MP) and maximum-likelihood (ML) generated comparisons of the 16S rRNA gene sequences revealed individual taxonomic positions. Also molecular (DNA-DNA hybridization test and determination of the DNA G+C content), physiological (API 20E, API 20NE, API 50CH and API ZYM tests) and biochemical and chemotaxonomic analyses (determination of respiratory quinone system and cellular fatty acid content) were investigated on the novel isolates. As results, six of them were determined to be four new species of three novel genera (Oceanicoccus, Psychrosphaera, Halicoccus) in the Gammaproteobacteria. Individualy, it was concluded that strains SA4-31, SA4-46 and SA4-48T should be classified as representing a new genus and species of the family Pseudoalteromonadaceae, for which the name Psychrosphaera saromensis gen. nov., sp. nov. is proposed. Strain PZ-5T represents a novel genus and species, for which the name Oceanicoccus sagamiensis gen. nov., sp. nov., is proposed. Two strains S1-36 T and S1- 72T present a novel genus and two species as Halicoccus marinus and H. pacifica were proposed. The genus Oceanicoccus and the genus Halicoccus formed a cluster with genera Spongiibacter, Melitea, Dasania, Haliea and Congregibacter at a family level, for which the name Dasaniaceae the Class Gammaproteobacteria, is proposed. Two strains SG-29T and S1-66T were determined to be two species of two novel genera (Rubricoccus, Aureimonas) belonging to the phylum Bacteroidetes. Also phylogenetic position based on 16S rRNA gene sequence, molecular, physiological and biochemical and chemotaxonomic analyses and cellular fatty acid content) were investigated. Strain SG-29T was classified as a novel genus and species, for which the name Rubricoccus marinus gen. nov., sp. nov., within family 'Rhodothermaceae', is proposed. Strain S1-66T represents a species of novel genus as Aureimonas marina was proposed. The other hands, about 300 colonies were isolated from about 20 species of marine sponge were investigated to find novel bacterial strains using medium P and SN. On the medium P screen results (107 colonies), 27 genera in the 5 classes were isolated from marine sponge. On the medium SN screen results (132 colonies), 29 genera in the 4 classes were obtained. Interestingly I didn't find any strain belong to the phylum Bacteroidetes and the other class that previously reported using culture independent methods. But I obtained some 6 candidates showed less than 96% partial 16S rRNA gene sequence similarity were re-sequenced of full 16S rRNA gene sequences and compared to data base information (Genbank) also respectively phylogenentic tree of six candidates were constructed. Finally strain MS-31T isolated from marine sponge Hymenicacidon flavia was classified as Sphingomonas jejuensis sp. nov., in the Alphaproteobacteria. I attempted to elucidate the phylogenetic position of nine novel isolates using a polyphasic taxonomic approaches 16S rRNA gene sequence, physiological, biochemical and chemotaxonomic analyses to characterize the novel strains. Based on the data it is present that these isolates represent 7 species of the 5 genera in the phylum Proteobacteria and Bacteroidetes.報告番号: 甲26922 ; 学位授与年月日: 2011-03-24 ; 学位の種別: 課程博士 ; 学位の種類: 博士(農学) ; 学位記番号: 博農第3675号 ; 研究科・専攻: 農学生命科学研究科応用生命工学専