Isolation And Identification Of Marine Actinomycetes Near The Coast Of Hainan And Excavation Of Natural Products Resistant To Staphylococcus Aureus

Staphylococcus aureus is one of the pathogens that seriously threaten human health.With the abuse of antibiotics,there are more and more reports about resistant strains of Staphylococcus aureus.The World Health Organization has listed Staphylococcus aureus as one of the important resistant bacteria in urgent need of new antimicrobial drugs.Therefore,it is urgent to develop new antimicrobial drugs.The special marine environment has bred a large number of novel marine actinomycetes,produced abundant and diverse secondary metabolites,and has become an important resource for the discovery of new antimicrobial drugs.In this study,138 marine actinomycetes were isolated from mangrove soil samplesand shallow sponge samples along the western coast of Hainan.These 138 actinomycetes were preliminarily identified by 16 S r RNA sequencing as belonging to eight actinomycetes genera: Streptomyces,Mycobacterium,Micromonospora,Pseudonocardia,Gordonia,Nocardioides,Pseudokineococcus and Amycolatopsis.Through multiphase taxonomic identification,strain HNM0687 was identified as a new species under the genus Gordonia.The isolated marine actinomycetes were screened for their bacteriostatic activity on agar blocks,from which 44 actinomycetes strains with anti-Staphylococcus aureus activity were screened.The activity of crude extracts from 44 actinomycetes obtained from primary screening was detected by small-scale fermentation.The results showed that crude extracts of metabolites from 32 strains had obvious anti-Staphylococcus aureus activity.The strain HNM0561 with excellent activity and abundant metabolites was selected from 32 actinomycetes by HPLC analysis for isolation and structure identification of metabolites.Through large-scale fermentation of strain HNM0561 to accumulate metabolites.A total of 24 monomer compounds were isolated from strain HNM0561 by various separation and identification methods,of which 4 were new natural products found for the first time.The structures of the isolated compounds include macrolides,macrolactams,spirocarbons,diterpenes,indoles,diketopiperazines and other structures,among which macrolides are the main products isolated in this study.The whole genome of actinomycete HNM0561 was combined with the analysis of metabolic gene clusters to locate possible biosynthetic gene clusters of some isolated compounds.Five macrolide compounds were tested for their activity against S.aureus.Three of them showed sobvious activity.The MIC values of three active compoundsagainst S.aureus were further tested.The results showed that the MICs were all below 32μg/m L,among which the optimal MIC reached 2 ～ 4 μg/m L,the titer is similar to that of the positive control Ampicillin,which has better application potential and is worthy of further development.