Biodiversity and antimicrobial activity of culturable actinobacteria isolated from Jiuliancheng Nur in Hebei Province

Abstract:

[Objective] To study the diversity and antimicrobial activity of culturable actinobacteria from dried Jiuliancheng Nur in Hebei Province, China. [Methods] Actinobacteria were isolated by using dilution plating technique with 15 media. Isolates were analyzed by comparison of 16S rRNA gene sequences. Crude extracts from fermented broth were obtained using ethyl acetate and from mycelia by acetone. Disk diffusion was used in antibacterial and antifungal assay and positive strains were further screened for PKS I, PKS II and NRPS antibiotics biosynthetic genes by PCR. [Results] A total of 251 actinobacterial strains, isolated from 11 soil samples, belonged to 31 genera affiliated with 15 families in 10 orders; and Streptomyces and Nocardiopsis are dominant genera. Out of these isolates, 57 were halotolerant or halophilic isolates, including 22 Nocardiopsis isolates and 15 Nesterenkonia isolates. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain J11Y309 is a prospective novel genus affiliated with the family Glycomycetaceae and J12GA03 is a prospective novel member affiliated with the family Mycobacteriaceae. Out of 96 fermented strains, 56 exhibited positive activity in antibacterial or antifungal assay, and the total positive rate reached 58.3%. Out of 56 positive strains, 47 carried at least 1 antibiotic biosynthetic gene and 17 strains carried all the 3 genes. [Conclusion] Jiuliancheng Nur shows a rich biodiversity of culturable medicinal actinobacteria, and it is a valuable source of novel antibiotics.