Study On Diversity And Antibiotic Activity Of Endophytic Isolated From Some Medicinal Plants

The actinobacteria, exist in various habitats of the nature, are a very important group of bacteria that has considerable value as prolific producer of antibiotics and other therapeutic compounds. As the important economic and other value, actinobacteria have attracted more and more researchers' attention. As complicated and various of the geological features and climate characteristics of Sichuan, there are many of medicinal plants and animals. Because of the long process of evolution, the endophytes of medicinal plants participate in biochemical pathways and produce analogous or novel bioactivc compounds. New endophyics may be very likely to be found in these medicinal plants. Therefore, endophytic actionbacteria of medicinal plants, a new class of microbial resource, have good potential. In this study, some endophytic actinobacteria were isolated from some medicinal plants in Yaan, Sichuan. Their diversity,phylogeny and antimicrobial activity were studied.One-hundred-six endophytic actinomycetes had been isolated from 7 medicinal plants which collected from Yaan. Five different isolation medium were used, they were HV medium, trehalose medium, modified Gause I medium, citrate medium and asparagine medium. The modified Gause I medium was the most effective medium. Thirty-three isolates were isolated from this medium. Whereas, the lowest number of strains were isolated form the citrate medium. Sixty-three strains were isolated from the roots of plants, which was the 59.5%of total isolates. On the other hand, there was only 7.5% of total isolates were isolated from the leaves.Forty-two strains were chosen for genetic diversity studied by 16S RNA PCR-RFLP and 10 representative strains were chosen for 16S rDNA sequencing. According to the 16S rNA PCR-RFLP analysis, all the strains were together at 66% similarity level. Six groups could be delineated at 73%similarity. The group II was the biggest group included 24 strains. According to the phylogenetic analysis, these strains belonged to genera Streptomyces, Oerskovia, Nonomuraea, Micromonospora, Nocardiopsis, Glycomyces and Cellulosimicrobium.Forty-two endophytic actinomyetes were studied on their antimicrobial activity with 2 pathogenic bacteria and 9 pathogenic fungi. Among them, about 90% strains had antimicrobial activity against Bipolaris maydis, and the maximum inhibition zone was 15mm. About 70% strains had antimicrobial activity against the Fusarium oxysporum, Curvularia lunata and Fusarium graminearum. But most of them did not inhibit against Verticilliam wilt and Escherichia coli. Most of the strains which showed good antibacterial activity were StreptomycesThe results indicated that endophytic actinomycetes isolated from medicinal plants in Yaan had high genetic and species diversity. These strains are provided important microbial resources for further search for novel bioactive compounds.