Diversity and antimicrobial activities of culturable endophytic actinomyces in the roots of Psammosilene tunicoides in Yunnan province

Abstract:

[Objective] To investigate the diversity of culturable endophytic actinomyces in the roots of Psammosilene tunicoides in Yunnan province and screen out the strains with high antimicrobial activities.[Methods]The roots of P.tunicoides from four different places in Yunnan province were pretreated at different temperatures, from which the culturable endophytic actinomyces were isolated with 14 media. The antimicrobial activities of 74 isolates against 5 pathogens were evaluated with inverted plates. [Results]Totally 121 strains of endophytic actinomyces were isolated from the roots of P.tunicoides. The results of 16S rRNA gene sequence alignments and phylogenetic analysis showed that the 121 strains could be categorized to 24 genera, 15 families of 10 orders. Streptomyces was the absolutely dominant genus, followed by Nocardia, Micromonospora, and Mycolicibacterium. D4 (0.3 g yeast powder, 0.3 g casein, 0.3 g glycose, 0.3 g bone meal) was the best medium for isolation among all the tested media and 80 ℃ was the optimal pretreatment temperature. Among 74 strains of endophytic actinomyces, 37 strains showed inhibitory activities against at least one indicator pathogen, and the main genus with strong antimicrobial activity was Streptomyces. [Conclusion] The roots of P.tunicoides harbor rich actinomyces and the functional strains with the ability to produce secondary metabolites, which can provide abundant strain resources for pharmaceutical and agricultural production in the future as well as basic data and a theoretical basis for the cultivation, protection, development, and application of P.tunicoides.