Biodiversity And Bioactivity Of Actinomycetes Associated With Castal Zone Soil Of Lianyungang City

In this paper, 155 actinomycetes(KLBMP 0001- KLBMP 0155) were isolated from the rhizospheres of coastal plants and soils, collected from Lianyungang coastal. After preliminary dereplication by morphological and cultural characteristics, 51 representative strains were chosen for 16 S rRNA gene sequencing, phylogenetic analysis and the biological activity assessment.Our results showed that these strains were affiliated with the phylum Actinobacteria and were distributed into six suborders, eleven families and seventeen known genera: Streptomyces, Nonomuraea, Actinomadura, Micromonospora, Verrucosispora, Pseudonocardia, Saccharopolyspora, Mycobacterium, Nocardia, Gordonia, Rhodococcus, Williamsia, Micrococcus, Agromyces, Promicromonospora, Isoptericola and Kribbella, which showed high diversity of culturable actinobacteria in this area. The genera Streptomyces, Saccharopolyspora and Nocardia were the predominant genera. Notably, strain KLBMP 0008 showed 96.58%(<97%) 16 S rRNA gene sequence similarity to the nearest type strain Streptomyces oceani SCSIO 02100 T, indicating that it should be a new species of the genus Streptomyces. Another strain, KLBMP 0043 showed highest 97.31% 16 S rRNA gene sequence similarity to its nearest type strain and displayed a distinct subclade in the phylogenetic tree, thus this strain could be a new species candidate and needs further polyphasic taxonomy research.The salt(NaCl) tolerance ability tests showed that 26 out of the 51 strains(31.4%) could grow on more than 10% NaCl agar media. The 155 isolated strains were subjected to plant growth promotion potential evaluation. The results indicated that 46.5% strains could grow on nitrogen-free agar media, 29.7% strains could produce indoleacetic acid, five strains could produce siderophore and eleven stains had the ability of phosphate solubilizing. The 51 representative strains were also subjected to antifungal enzyme-producing screening. We found that 16 strains could inhibit the growth of at least one of the fungal pathogens and strain KLBMP 0051 had broad spectrum antifungal activity to all the pathogens. The enzyme screening displayed that 45% strains produce protease, 51% strains produce amylase, while the percentages for chitinase, cellulose and xylanase producing were 33.3%, 37.3% and 25.5%.In summary, in this study, actinomycetes were successfully isolated from the rhizospheres of coastal plants and soils, collected from Lianyungang coastal and diverse rare actinobacteria were obtained, including two new species candidates and some bioactive strains. The present study demonstrated that prolific actinobacteria existed in the coastal soils and many of them had bioactivity, which could be the good and potential new microbial resources for exploitation. Our research provides the scientific basis for further understanding the ecological function and the resource utilization of coastal plant associated actinobacteria.