Bioprospecting and bioactivity screening of culturable actinobacteria from color desert in Dengpa, Tibet

Abstract:

[Background] The problem of bacterial drug resistance is becoming more and more serious. The development of new antibiotics far lags behind the clinical needs. The discovery of microbial drug resources from special habitats is expected to solve this problem. [Objective] Biodiversity and bioactivity screening of actinomycetes from color desert in Dengpa, Tibet were performed, which would lay a good foundation for discovery of the resources of medicinal actinomycetes and new antibiotics. [Methods] The actinobacterial strains were cultured on 8 different media. Biodiversity of actinobacterial strains were analyzed according to 16S rRNA gene sequences. Detection of PKS-II (ketosynthase, KS), NRPS (adenylation A domain), AHBA and Halo genes was performed by PCR and agarose gel electrophoresis. Screening of antimicrobial activity was carried out by filter paper method. Antioxidant ability including total antioxidant activity, hydroxyl and oxygen free radical scavenging rate was tested by the chemical method. [Results] a total of 231 strains were isolated from four soil samples from color desert in Dengpa, Tibet. 16S rRNA gene analysis revealed these strains were affiliated with seven actinobacterial genera. Streptomyces was the dominant genus. Screening of biosynthetic gene clusters showed that 68 strains had at least one of four biosynthetic gene clusters and 6 strains had all the tested biosynthetic gene clusters. Furthermore, secondary metabolites produced by these strains showed antimicrobial activity against certain pathogens and antioxidant capacity towards hydroxyl and oxygen free radical scavenging. Therein, eight strains displayed broad-spectrum antimicrobial activity. Thirteen strains showed the positive total antioxidant activity. Ten strains had good hydroxyl free radical scavenging and three strains showed positive oxygen free radical scavenging. [Conclusion] These results exhibited that there are abundant actinomycetes medicinal resources in color desert in Dengpa, Tibet, which was promising for discovering new strains of actinomycetes and developing new antibiotics.