Endophytic bacteria diversity of Aspidistra Ker-Gawl. and their antimicrobial activities

Abstract:

[Background] Medicinal plants constitute the huge diversity of endophytic bacteria. These microbes have potential to synthesis of numerous novel compounds that can be exploited in pharmaceutical industries. [Objective] For the purpose of exploring the pharmaceutically potential of the endophytes in medicinal plants and finding antimicrobial secondary metabolites, endophytic bacteria diversity of Aspidistra Ker-Gawl. was investigated. [Methods] After surface sterilization, the tissue fragments of 13 plants, which were classified into 9 different species, were inoculated onto 5 diverse isolation media. Duplicate isolates were eliminated by colony properties. Based on 16S rRNA gene sequencing results, Neighbour-Joining phylogenetic tree was constructed to analyze the endophytic bacteria diversity in Aspidistra spp. All the non-duplicated isolates were fermented with two kinds of media. The antimicrobial activities of the endophytic motablisms were detected with 5 testing strains, including Mycobacterium smegmatis ATCC 700044, Xanthomonas oryzae PXO99A, Candida albicans ATCC 10231, Klebsiella pneumoniae ATCC 700603 and resistant strain Enterococcus faecalis HH22. [Results] A total of 234 endophytic bacteria were isolated from different plant tissues and 156 non-duplicated strains were confirmed after colony properties checking. These endophytic bacteria strains were classified into 3 phyla, 10 orders, 22 families and 29 genera. Notably, Streptomyces sp., Bacillus sp., Microbacterium sp., Paenibacillus sp. and Rhizobium sp. were the predominant species in Aspidistra spp., and 6 potential novel species were found. The fermentation broth from 38 isolates (23.7%) showed antimicrobial activities. [Conclusion] The data of this study showed an unexpected diversity of endophytes inside the Aspidistra tissues, and suggested that endophytic bacteria of the Aspidistra tissues are promising sources of new natural secondary metabolites with favorable antimicrobial activities.