| Microbial natural products have been the major source for lead compounds. However, a large amount of screening for microorganism from some convergent environments such as soil and water more than half a century, which has led to the compounds isolated from microorganism are often known and the odds of discovering active compounds with a novel structure is already low. Therefore, many scholars suggest screening microbial and a ctive compounds from a new habitat. As special environmental microorganisms, insect symbiotic actinobacteria have yielded many compounds with novel structures, and their continued mining holds much promise for the discovery of microbial drug. This paper is aimed at researching the diversity of symbiotic actinobacteria in Camponotus janponicus Mayr using culture-dependent approaches, and further screening and evaluating their antimicrobial activity, which lay the foundation for further study on bioactive secondary metabolites.Six media were used to isolate symbiotic actinomycetes from the different structures of Camponotus janponicus Mayr and analyzing the quantity of actinomyctes isolated from the different media and structures as well as screening antimicrobial activity. Moreover, constructing phylogenetic tree based on 16 S r RNA gene sequences of all the sequenced isolates to analyze diversity of culturable actinomycetes. The results are as follows:(1) A total of 116 culturable actinomycetes were successfully isolated from Camponotus janponicus Mayr after dereplication of 124 actinomycetes by using six different media.(2) It is showed that the amount of actinomycetes isolated from the structure of head is maximum, up to 67.2%, followed by cuticle, and the amount of actinomycetes isolated from thorax and abdomen is relatively less.(3) There are 19 strains showing antimicrobial activity in antimicrobial activity test of symbiotic actinomycetes. Among them, 16 strains showed antifungal activity against more than 5 pathogenic fungi; 14 strains showed better antifungal activity against more than 5 pathogenic fungi; 10 strains showed antifungal activity against one or more pathogenic fungi with more than 50% inhibiting rate. It is indicated that active strains are mainly derived from head and followed by cuticle.(4) Based on the morphology of the colonies and the 16 S r RNA gene sequences of some actinomycetes, these strains were classified into eight genera including Streptomyces, Promicromonospora, Micormonospora, Nonomuraea, Verrucosispora, Phytohabitans, Microbispora and Nocardia. Among of which, the greatest proportion is Streptomyces(89.7%).(5) It is showed that different species in the genus of Streptomyces separated from each and could cluster into different branches, according to the analysis of phylogenetic tree based on the 16 S rRNA gene sequences. Furthermore, the rare actinomycetes in different genera were also cluster into different branches, which showed that symbiotic actinomycetes in Camponotus janponicus Mayr were diverse.(6) It is found that 3 strains maybe represent novel species after analysis of the 16 S r RNA gene sequence and characterized using the polyphasic approach. It is showed that strain 1H-HV4 represented a novel species of the genus Nocardia and for which the name Nocardia camponoti is proposed, the designation of this strain is valid and published in International Journal of Systematic and Evolutionary Microbiology; strain 1H-GS9 represents a novel species of the genus Streptomyces, for which the name Streptomyces formicae is proposed, the designation of this strain is valid and published in Antonie van Leeuwenhoek; strain 1C-HV12 represents a novel species of the genus Promicromonospora, for which the name Promicromonospora alba is proposed, the designation of this strain is valid and published in International Journal of Systematic and Evolutionary Microbiology.There are great diverse actinomycetes inside Camponotus janponicus Mayr and they have great antimicrobial activity, which show a great potential for researching new bioactive compounds. |
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