Identification Of Endosymbiotic Actinobacteria Of Ants And Study Of Their Metabolites With Antimicrobial Activity

Recently,scientists findings indicated that endophytic organisms could produce a large variety of secondary metabolites,and several novel compounds with antimicrobial activity had been isolated from mutualistic bacteria,particularly those that protect their host against pathogens.Defensive bacterial symbionts of eukaryotes constitute especially promising candidates for the production of antibiotics with potential applicability in human medicine,because the compounds involved should not harm the eukaryotic host and are therefore also less likely to have harmful side effects on humans.So,in recent years,more and more attention has been paid to the insect symbiotic actinomycetes,and further research on protective symbioses will undoubtedly continue to yield novel antibiotics that might prove valuable in the arms race against increasingly resistant human pathogens.In this study,30 strains of endosymbiotic bacteria were selected as materials,cultivative morphological characteristics,biological activity and 16 S rRNA gene sequence similarity studies showed that the strain 3H-GS17 T and 2H-TWYE14 T maybe a novel species belonged to Actinocorallia and Streptomyces,respectively,and 1H-GS2 had good bioactivity in resisting fungi,so,the new speices are identified in a polyphasic approach and the bioactive constituents were isolated and identified from these symbionts actinobacteria.The results are as follows:(1)16S rRNA gene sequence similarity studies showed that strain 3H-GS17 T belongs to the genus Actinocorallia with high sequence similarities to Actinocorallia glomerata JCM 9376T(98.13%)and Actinocorallia longicatena JCM 9377~T(97.64%).The chemotaxonomic properties of strain 3H-GS17 T are also consistent with those members of the genus Actinocorallia.A combination of DNA–DNA hybridization experiments and phenotypic tests were carried out between strain 3H-GS17 T and its closely related strains,which further clarified their relatedness and demonstrated that 3H-GS17 T could be distinguished from these strains.Therefore,the strain is concluded to represent a novel species of the genus Actinocorallia,for which the name Actinocorallia lasicapitis sp.nov.is proposed.The type strain is 3H-GS17~T(=DSM100595T=CGMCC 4.7282T).(2)16S rRNA gene sequence analysis showed that strain 2H-TWYE14 T belongs to the genus Streptomyces with the highest sequence similarity to Streptomyces niveus NRRL 2466T(98.84%).gyr B gene analysis also indicated that strain 2H-TWYE14 T should be assigned to the genus Streptomyces.The chemotaxonomic properties of strain 2H-TWYE14 T are consistent with those members of the genus Streptomyces.A combination of DNA–DNA hybridization experiment and phenotypic tests were carried out between strain 2H-TWYE14 T and its phylogenetically closely related strain S.niveus JCM 4251 T,which further clarified their relatedness and demonstrated that2H-TWYE14 T could be distinguished from this strain.Therefore,it is concluded that strain2H-TWYE14 T can be classified as representing a novel species of the genus Streptomyces,for which the name Streptomyces camponoticapitis sp.nov.is proposed.The type strain is2H-TWYE14~T(=DSM 100523T=CGMCC 4.7275T).(3)The bioactivity of isolated endosymbiotic actinobacteria was performed with using an in vitro screening technique,one strain with good biological activity were found from these endosymbiotic actinobacteria.The fermentation products of strain 1H-GS2 showed good antifungal activity.After separation and purification of the fermentation products,one known compounds,albonoursin,was isolated and identified from 1H-GS2.