Diversity Of Cultivable Bacteria Isolated From Caroline Seamount In The Western Pacific And Taxonomic Analysis Of Two Novel Marine Bacteria

The seamount is special habitat in the deep sea.Because of its specific hydrological conditions and geography characteristics,there are the special deep-sea microbial communities in the seamount.Bacteria are one of the oldest organisms on earth.Studying on microorganisms of seamount not only help understand the origin of life,but also make use of the resource of marine microorganisms at a deeper level.This study focused on the diversity of cultivable bacteria of the biological samples and seawater samples collected from Caroline Seamount in the Western Pacific.Bseides,the taxonomic statuses of two strains were studied by the polyphasic taxonomy approach.The diversity of marine bacteria was examined based on 16S rRNA gene sequence analysis.A total of 248 representative strains were selected from1200 isolates,and were further sequenced and the phylogenetic analysis was carried out.The results showed that 93 strains isolated from biological samples were composed of 5 major lineages including?-Proteobacteria?53%?,Firmicutes?21%?,?-Proteobacteria?10%?,Actinobacteria?10%?and Bacteroidetes?6%?,and belonged to 6 classes and 45 genera.?-Proteobacteria was the dominate group.The dominat genera were Alteromonas?Halomonas?Pseudomonas and Pseudoalteromonas,which distributed widely on the surface of different biology in Caroline seamount.In addition,strain KL614 belonging to Bacillaceae was the potential new genus.155 strains isolated from seawater samples were composed of 5 major lineages including?-Proteobacteria?45%?,?-Proteobacteria?27%?,Actinobacteria?16%?Firmicutes?7%?and Bacteroidetes?5%?,and belonged to 5 classes and 64 genera.?-Proteobacteria was the main group.The dominat genera were Marinobacter?Alteromonas?Pseudoalteromonas?Microbacterium?Roseovarius and Photobacterium,which were isolated from seawater at different depths in Caroline seamount.In addition,6 strains were the potential new species,including strains KL412,KL2260,KL658,KL2666,KL208 and KL2576,which respectively belonged to Pseudoruegeria,Vibro,Winogradskyella,Pseudoroseicyclus,Stakelama and Glycocaulis.Strain KL633 belonging to Vibrionaceae was the potential new genus.Two novel bacteria isolated from the seamount in the tropical Western Pacific were classified and identified,which were designed YC973^T and YC1039^T.Cells of strain YC973^T were Gram-stain-negative,non-flagellated,gliding,strictly aerobic and rod-shaped?approximately 1.5-3.2?m in length and 0.3-0.5?m in width?.Colonies on marine agar?MA?were yellow-colored.Strain YC973^T was found to be able to grow in media with 0.5%-6%?w/v?NaCl,at 4-41?on MA,at pH6.0-9.0.The polar lipid profile was phosphatidylethanolamine?PE?.The predominant cellular fatty acids were iso-C_15:0?24.31%?,iso-C_15:1 G?18.7%?,summed feature3?9.67%?and an unknown fatty acid of equivalent chain-length 13.565?12.28%?.Cells of strain YC973^T were catalase positive and oxidase positive.It could hydrolyse aesculin and gelatin.The genomic DNA G+C content of strain YC973^T was 36.1 mol%.Phylogenetic analysis based on its 16S rRNA gene sequence showed that strain YC973^T related to the genus Maribacter and had high 16S rRNA gene sequence similarity to Maribacter orientalis KMM 3947^T?97.6%?.On the basis of the evidence presented in this study,strain YC973^T represented a novel species of the Maribacter genus which belonged to Flavobacteriaceae,for which we proposed the name Maribacter marinus.Cells of strain YC1039^T were Gram-stain-negative,non-flagellated,non-spore-forming,gliding and rod-shaped?approximately 1.6–2.5?m in length and0.5–0.6?m in width?.Colonies on marine agar?MA?were yellow-colored.Strain1039^T was found to be able to grow in media with 0.5%-5%?w/v?NaCl,at 4-41?on MA,at pH6.0-9.0.The predominant cellular fatty acids were iso-C_15:1 G?34.0%?and iso-C_15:0?24.2%?.The polar lipid profile was phosphatidylethanolamine?PE?.Strain1039^T was catalase positive and oxidase positive.Nitrate was not reduced.It could hydrolyse aesculin,gelatin,DNA,Tween 60,Tween 80,casein and starch.The genomic DNA G+C content of strain YC1039^T was 29.8 mol%.Phylogenetic analysis based on its 16S rRNA gene sequence showed that strain YC1039^T related to the genus Mesoflavibacter and had high 16S r RNA gene sequence similarity to Mesoflavibacter sabulilitoris KCTC 42117^T?98.3%?.On the basis of the evidence presented in this study,strain YC1039^T represented a novel species of the genus Mesoflavibacter which belonged to Flavobacteriaceae,for which we proposed the name Mesoflavibacter profundi.