Diversity Of Marine Actinomycetes In Different Environments And Taxonomic Analysis Of 2 Novel Actinomycetes

The diversity of marine actinomycetes isolated from different environments was studied based on comparative study of different isolation methods by pure cultures and 16S rDNA sequence-based phylogenetic analysis, and the strains were screened for antibacterial activity and enzymatic activity. The main results are as follow:1. Study of different isolation methods of marine actinomycetes: The impacts of different sample preparation methods, type of diluents, seawater concentration and culture medium on the isolation of actinomycetes from the inter-tidal mud at Qingdao were investigated. The results showed that samples pretreated with 55°C for 6 minutes, grow on the culture media made of pure seawater and diluted with 1/4 Ringer's solution can improve the isolation of actinomycetes. The medium M1,M6,M7 and M8 are more effective when compared to others.2. Study of the diversity of marine actinomycetes from sediments of the Yellow Sea Cold Water Mass: In this study, 172 actinomycetes were isolated by using four culture media which are more effective on separation of actinomycetes. Bioinformatics analysis of the 16S rDNA sequences from the 51 representative isolates can be assigned to five actinobacteria genera (Streptomyces Nocardiopsis, Actinoalloteichus, Micromonospora and a novel genus). Out of 172 isolates, 58 isolates exhibited antimicrobial activity against human pathogens, and 94 isolates can produce three kinds of enzymes simultaneously.3. Isolation and screening of actinomycetes from Arctic marine sediments: In this study, 109 actinomycetes were isolated using six different culture media. Bioinformatics analysis of the 16S rDNA sequences from the 34 representative isolates can be assigned to three genera (Streptomyces, Pseudonocardia and HNocardiopsis). Out of 109 isolates, 39 isolates exhibited antimicrobial activity against human pathogens.4. Isolation and culture of actinomycetes from a salt pond, Qingdao: In this study, 15 actinomycete were isolated using three different media. Bioinformatics analysis of the 16S rDNA sequences from the isolates can be assigned to three genera (Streptomyces, Nocardiopsis and a novel genus). Out of 15 isolates, 12, 3, 2 and 1 isolates produces amylase, lipase, caseinase and cellulose accordingly.5. Taxonomic analysis of Spinactinospora alkalitolerans gen. nov. sp. nov.: The strain CXB6542~T formed branched substrate mycelium without fragmentation. Abundant aerial mycelium differentiated into long or short chains of spores, and the spores were elliptic and cylindrical with spinous surface. Strain CXB6542~T required NaCl for growth, and contained ribose and glucose as the major whole-cell components. Comparative analysis of 16S rDNA sequence showed that the novel strain was most closely related to genera within the family Nocardiopsaceae, but formed a separate lineage. The strain CXB6542~T had only 96.6%, 96.5% and 96.1% similarity to the standard strains with the closest relationship respectively. On the basis of phenotypic, chemotaxonomic and phylogenetic distinctiveness, strain CXB6542~T was considered to represent a new genus and species in the family Nocardiopsaceae, and the name Spinactinospora alkalitolerans gen. nov. sp. nov. is proposed.6. Taxonomic analysis of Salinactinospora qingdaonensis gen. nov. sp. nov.: The strain CXB832~T formed pale-yellow to deep yellow and branched substrate mycelium without fragmentation. Abundant white aerial mycelium differentiated into long chains of spores, and the spores were rod-shaped with smooth surfaces. Optimal growth occurred at 9～12% (w/v) NaCl. Strain CXB832~T contained glucose and xylose as the major whole-cell components. BLAST results for the 16S rDNA sequence of strain CXB832~T showed that its closest relatives were members of genera Nocardiopsis and Haloactinospora in the family Nocardiopsaceae, with the highest gene sequence similarity of 95.4% and 94.9% with the standard strains respectively. The 16S rDNA based neighbour-joining and maximum-likelihood trees showed the phylogenetic relationship between strain CXB832~T and the closely related genera, and that strain CXB832~T formed a separate lineage. On the basis of phenotypic, chemotaxonomic and phylogenetic distinctiveness, strain CXB832~T was considered to represent a new genus and species in the family Nocardiopsaceae, and the name Salinactinospora qingdaonensis gen. nov. sp. nov. is proposed.