Study On The Diversity Of Culturable Actinobacteria And Their Antibacterial Activities In Karst Caves From Guizhou Province,China

There are rich resources of Karst caves,but the study of cave environmental microbial resources is still in its embryo in China.In this study,we mainly explored the diversity and distribution of actinobacteria in karst caves of Xingyi and Libo,Guizhou Province,and also detected their antimicrobial activities on those isolated actinobacterial strains,to explore potential novel active products.A total of 458 actinobacterial strains were isolated and purified by using a variety of isolation media in different types of samples in the karst cave environment of Guizhou.According to the morphological characteristics of actinobacteria,the results showed that there were 193 species and 44 genera in 22 families and 11 order of actinomycetes.By 16S rRNA gene sequence alignment,15 species with less than 98.5%similarity were found,and the main distribution groups were those members in genera Nocardia,Streptomyces,Rhodococcus,Nocardioides,Microlunatus and Kineococcus as rare species distribution.Total 218 strains of actinobacteria were screened for antibacterial activity.The results showed that 16 of the 81 active strains had antibacterial activity against these 10 indicator strains,showing a strong inhibitory effect.There are 46 strains of at least three kinds of indicator bacteria have antibacterial effect.Among these active strains,most of the strains exhibiting strong antibacterial activity were Streptomyces and Micromonospora,and were also distributed among other groups.The results show that the karst cave actinobacterial resources have great potential for the development and application of active natural products.Through the morphological,physiological and biochemical characteristics,chemical compositions and phylogenetic analysis,and DNA-DNA hybridization experiments,three new species(Nocardioides cavernae sp.nov.,Nocardia cavernae sp.nov.and Lentzea cavernae sp.nov.)were identified by polyphasic taxonomy method.In this research,the diversity of the karst cave actinobacteria in Guizhou was established by means of pure culture method.In addition,the screening results of the antimicrobial activity of isolated strains revealed that the karst caves contained a large number of strains with active natural products,and provided special fungus resources for the screening of novel and active products.