Preliminary study on the diversity and antimicrobial activity of actinomycetes from Shuanghe Cave：A case study of Yinhedong and Shanlindong

Actinomycetes are important microorganisms in medicinal fungus, from which antibiotics inmedication has been regarded as the most dazzling pearl in the 20th century. However, with the abuse of antibiotics, antibiotic resistance phenomenon has become increasingly serious.It is hence necessary to discover new actinomycete species from special ecological environment to overcome the problem of drug resistance to existing antibiotics.This study aims to analyze the diversity and antimicrobial activity of actinomycetes discovered from Yinhedong and Shanlindong caves, the branches of the Shuanghe cave system, by using cultivation-dependent method to isolate the actinomycetes from the samples collected in the two caves.The diversity was analyzed by comparison of 16S rRNA gene sequences.The antifungal and antimicrobial activity of the fermentation products of the isolates were tested by paper disk diffusion method. Screening of PKS I, PKS II and NRPS genes of the strains were carried out by PCR and agarose electrophoresis.Result shows that the isolates obtained by pure culture distribute in 10 different genera affiliated with 7 families. Antimicrobial assay show that 32 among 66 strains exhibit positive results of antifungal or antibacterial response; and the total positive rate was 48.5%. PCR results show 31 strains have at least one biosynthetic gene including NRPS, PKS I and PKS II, of which 28 strains have NRPS gene, 17 strains have PKS I gene and 21 strains have PKS II gene. It is also noted that 12 strains have the all three biosynthetic genes.Conclusion: The study preliminarily indicates that the resource of actinomycetes in the Shuanghe cave system is abundant, which deserves for conducting further study.