Selective Isolation Of Rare Actinomycetes From Marine Environment And Identification Of Novel Strain

Actinomyces distribute widely in nature,which encode a wealth of natural product biosynthetic gene clusters,such as the synthesis of non-ribosomal peptides,type I and type II polyketides and so on.It also produces secondary metabolites with diverse biological activities and structure features,which are important sources of antibiotics,immunosuppressive and enzymes inhibitors.There are about 70%of natural antibiotics are produced by actinomycetes,especially streptomyces.However,with the continuous development and utilization of streptomyces,it has become more and more difficult to discover novel strains and natural products.In order to discover new bioactive compounds,it is reasonable to focus on underexplored environments,such as the marine environment,and screen strains that could produce novel bioactive compounds,such as rare actinomycetes.The particularity of the marine environment,which gives marine actinomycetes the special physiological and biochemical characteristics and unique metabolic pathways,leading to produce new structures of secondary metabolites.Therefore,marine actinomycetes is a kind of valuable resources of medicinal microorganisms.In this study,we collected 14 marine samples from deep sea sediments and sulphide,and mangrove plant rhizosphere.PLA medium,ISP5 medium,SC medium,Proline-MOPS medium,R2A medium,and 2216E medium were used for rare actinomycetes isolation.A total of 206 actinomycetes were isolated from these marine environment samples.The repetitive strains were excluded by comparison of the morphological characteristics,antimicrobial and antitumor activity.According to the 16S rRNA gene identification results of 109 strains,106 strains(51.5%)were classified as rare actinomycetes,which belongs to 7 genus,including Nocardiopsis(92 strains),Nonomuraea(4 strains),Nocardia(4 strains),Microbacterium(3 strains),Pseudonocardia(1 strain),Brevibacterium(1 strain),and Kocuria(1 strain),and olny three strains were Streptomyces.Strain XMU 110 was analyzed by polyphasic taxonomy methods,including morphological,physiological,biochemical and molecular characteristics,and identified as a novel species of the genus Nonomuraea,respectively.Strain XMU 110 was named as Nonomuraea ceibae.145 stains were fermented under both conditions of solid and liquid.Bioactivities of the total 290 crude extract were evaluated in this study.The antimicrobial activity were detected by filtering paper method,using Staphlococcus aureus,Bacillus subtilis,Bacillus pumilus,Escherichia coli,Aspergillus niger and Candida albicans as indicators.There are 106 strains(73.1%)showed inhibitory effect on one or more indicator microorganisms.While the antitumor activity were detected by MTS method against human breast cancer cells MCF-7 and MDA-MB-231,human osteosarcoma cancer cells U20S,human liver cancer cells HepG2,human esophageal carcinoma cells kyse-450,human promyelocytic leukemia cells HL-60,human mantle cell lymphoma cells JEKO-1,human melanoma cells A375,and human gastric cancer cells BGC-823.There are 66 strains(45.5%)showed inhibitory effect against one or more cancer cells.In summary,our results shows that actinomycetes resources in marine environment are very abundant,and many strains have bioactivities.The results suggest that actinomycete from marine environment represents a kind of potential resources with diverse bioactivities.