Evaluation of Antagonistic Activity of Actinobacteria in Saxicolous Lichens

Actinobacteria are important producers of novel bioactive compounds. New sources need to be explored for isolating previously unknown bioactive compound-producing actinobacteria. We evaluated the potential of saxicolous lichens as a natural source of novel bioactive actinobacterial species. Saxicolous lichen samples were collected from three climatic belts at different elevations (1600–3400 m) on Qin Mountain, Shaanxi Province, China. Actinobacteria were cultivated, enumerated, and isolated using serial dilution and spread-plate techniques under normal nutrient and oligotrophic conditions. Antimicrobial activity of actinobacterial isolates was analyzed using an agar block method against fifteen typical bacterial and fungal species and plant pathogens. The dominant isolates and isolates with broad-spectrum antagonistic activity were identified by 16S rRNA-based sequence analysis. Results showed that colony counts, total number of species, and the number of bioactive species of actinobacteria in saxicolous lichens were higher in elevation 3000 m. The dominant isolates were classified into 42 species of 10 genera. Antagonistic activities were detected in approximately 66% of the actinobacteria isolates. Of these, 42 isolates (28%) showed broad-spectrum antagonistic activity against ≥5 microorganisms tested. In conclusion, the saxicolous lichen possesses a high diversity of actinobacteria and serves as a natural source of bioactive compound-producing actinobacteria. © 2017 Friends Science Publishers