Diversity And Polyphasic Taxonomy Of Epiphytic Bacteria Isolated From Macroalgae

Algae are extremely important resources in the marine environment.They have a wide variety of species and play important roles in marine ecosystems as primary producers.There are complex interactions between algal epiphytic microbes and algae,mainly including mutually beneficial symbiosis,antagonism and competition.These epiphytic microbes have played particular ecological roles in phycospheres.The isolation and systematic identification of cultivable algal epiphytic bacteria is to obtain these particular microbial resources for further studies on their metabolic characteristics,ecological function and application.In this thesis,the epiphytic bacteria were isolated from Polysiphonia samples collected from Ny-(?)lesund,Arctic using the dilution plating method and their diversity were studied based on the 16S rRNA gene determination and analysis;in addition,two bacteria respectively isolated from Ulva pertusa and Colpomenia sinuosa samples collected from Rongcheng offshore sea were taxonomically characterized using a polyphasic taxonomic approach and their taxonomic positions were finally determined based on their phenotypic,chemotaxonomic and phylogenetic characteristics.1.Diversity of cultivable epiphytic bacteria isolated from Arctic macroalga Polysiphonia sp.A total of 60 cultivable epiphytic bacteria strains were isolated from the Arctic red macroalga sample(Polysiphonia sp.)collected from Ny-(?)lesund,Arctic using the dilution plating method.Analysis of the 16S rRNA gene sequences revealed the isolated strains belonged to twelve genera in four phyla(Proteobacteria,Actinobacteria,Bacteroidete and Firmicutes).The dominant genera are Pseudoalteromonas(12 strains)and Psychrobacter(22 strains)which belonged to the phylum Proteobacteria and Salinibacterium(10 strains)which belonged to the phylum Actinobacteria.2.Polyphasic taxonomy of strain SM1966^TA Gram-stain-negative,aerobic,rod-shaped bacteria,polarly flagellated,designated strain SM1966^T,was isolated from the surface of an Ulva pertusa sample collected off the offshore sea of Rongcheng,China.Strain SM1966^T grew at 5-30??,and with 0.5-8.5%(w/v)Na Cl.The major fatty acids of strain SM1966^T were summed feature 3(C_16:1?6c/C_16:1?7c),summed feature 8(C_18:1?7c)and C_16:0,with their predominant polar lipids being phosphatidylethanolamine and phosphatidylglycerol and the solo respiratory quinones being Q-8.The genomic DNA G+C contents of strain SM1966^T determined from genomic sequences was41.6%.In the Phylogenetic trees based on the 16S rRNA gene,SM1966^T formed distinct phylogenetic branches with Marinomonas blandensis(96.7%).On the basis of the polyphasic evidences presented above,strain SM1966^T was considered to represent a novel specie within the genus Marinomonas,for which the name Marinomonas algicola sp.nov.was proposed.3.Polyphasic taxonomy of strain SM2066^TA Gram-stain-negative,aerobic,rod-shaped bacteria,polarly flagellated,designated strain SM2066^T,was isolated from the surface of a Colpomenia sinuosa sample collected off the offshore sea of Rongcheng,China.Strain SM2066^T grew at 8-37??,and with 0.5-7.0%(w/v)NaCl.The major fatty acids of the strain SM2066^T were summed feature 3(C_16:1?6c/C_16:1?7c),summed feature 8(C_18:1?7c)and C_16:0,with their predominant polar lipids being phosphatidylethanolamine and phosphatidylglycerol and the solo respiratory quinones being Q-8.The genomic DNA G+C contents of strain SM2066^T determined from genomic sequences was40.3%.In the Phylogenetic trees based on the 16S rRNA gene,SM2066^T formed distinct phylogenetic branches with Marinomonas ushuaiensis(97.9%).On the basis of the polyphasic evidences presented above,strain SM2066^T was considered to represent a novel species within the genus Marinomonas,for which the name Marinomonas colpomeniae sp.nov.was proposed.