Symbiotic Actinomycetes And Its Secondary Metabolites Associated With Meson Bee Osmia Cornifrons

With the improper use of antibiotics,the phenomenon of resistance to pathogens has become more and more serious,and multiple drug resistance has appeared frequently in common pathogens.Therefore,new antibiotics need to be found constantly in clinical practice.Insect symbiotic microorganisms are often located in insect guts,rind,or reservoirs,and establish a special survival-dependence relationship with the host.Special micro-habitats often result in symbiotic microorganisms producing novel secondary metabolites with structural features.The symbiotic actinomycetes of the Hymenoptera insects often produce antifungal,antibacterial active compounds that assist the host or its larvae against infection by pathogens and provide protection for their food.Therefore,the Hymenoptera insect symbiotic actinomycetes are important sources of new antifungal and antibacterial activity natural products.Osmia cornifrons is an insect pollinator of the genus Echinocactus of the Hymenoptera.Artificially acclimated O.cornifrons often use reed tube as a nesting room,where they are divided into nests and spawned to progeny.O.cornifrons were collected in Yantai and Weihai.A total of 38 strains were isolated.Based on the 16S rDNA gene sequence identification and phylogenetic tree construction for diversity analysis,the strains were identified as belonging to 6 genera of actinomycetes:26 Streptomyces,4 Micromonospora,3 Nocardia,1 Actinocorallia,3 Actinomadura and 1 Pseudonocardia strain.The antifungal and antibacterial activities of 38 actinomycetes and their fermentation broth were screened using using the method of mash screen method and disk diffusion method.It was found that Streptomyces sp.OC1403-4 and Streptomyces sp.OC1403-6 had good antibacterial activity against Escherichia coli,Staphylococcus aureus and Bacillus subtilis with inhibition zone 14-18 mm,Streptomyces sp.OC 1401-2 exhibited inhibitory activity against E.coli,S.aureus and B.subtilis with inhibition zone 11-14 mm;Streptomyces sp.OC1611-8A and Streptomyces sp.R1706-8 showed antifungal active against all indicator strains with an inhibitory diameter of 10-25 mm.Metabolites of Streptomyces sp.OC1401-2,OC1611-8A,and R1706-8 were separated by column chromatography,and 9 compounds were identified by spectral analysis,including manumycin-type derivatives,sesquiterpenoid,esters and other small molecules.Two manumycin-type derivatives,one sesquiterpenoid and two long-chain ester compounds are new compounds,and manumycin-type derivatives are named cornifronin A and B.The identified compounds were three manumycin-type derivatives(cornifronin A,cornifronin B,Antibiotic SW-B),one sesquiterpenoid(OC1611-ST03),two ester compounds(R1706-SH01,81706-SH02)and tyrosol,thymine,uracil.The manumycin-type derivatives,sesquiterpenoid and ester compounds were tested for their antibacterial activity.The antibacterial activity of the compounds was determined by disk diffusion method,minimum inhibitory concentration(MIC)and minimum bactericidal concentration(MBC).Three manumycin-type derivatives and two ester compounds were active against the tested strains.NO inhibitory activity and cytotoxicity assays were performed on OC1611-ST03 and no activity was found,and the hexokinase ? activity was tested with an IC50 of 124.3 ?M.