Genome Mining Of Antibiotic Resources In Streptomyces Qaidamensis S10~T

The Natural products of microorganisms have always been important sources of discovery of new drugs because its diverse structures and bioactivities,many of which have been applied as drugs helpful for human and animal.The development of genome sequencing markedly influenced biological research,especially the research of natural products.The information on genome suggest that Streptomyces have great potential for biosynthesis.Streptomyces,a kind of Gram-positive bacteria,can produce lots of secondary metabolites that are widely used in the pharmaceutical industry,food processing and agriculture production.Streptomyces in extreme environments of extreme cold,hot,over-acid,and high salinity have attracted widespread attention of researchers due to their special physiological and biochemical properties.However,the problem of bacterial drug resistance has seriously been harming human health with multidrug-resistant bacteria discovered all over the world.Traditional separation methods help us obtain a large number of antibiotic precursor molecules,but it now becomes difficult to find novel compounds with good activity by these methods.Therefore,it's urgent to use genome mining to develop new antibiotic precursor molecules.Genome mining uses the genome information of microorganisms to predict potential of synthetic natural products,and then obtain new natural products through genetic engineering.Discovering new active natural products from Streptomyces in extreme environment by genome mining technology is an innovative strategy.Streptomyces qaidamensis S10~T,the research object of this thesis,is screened from the sand samples of Qaidam Basin located in the northwest of the Qinghai Province.The Streptomyces strain is a new species in extreme environment with high saline.Its fermentation crude extract has obvious biological activity against methicillin-resistant Staphylococcus aureus,which suggests that the secondary products produced by the strain have potential to develop into antibiotics.However,S10~T's natural products have not been well studied.The thesis carried out a preliminary genome mining study of S10~T by antiSMASH.Gene sequence analysis suggesting that S10~T has strong ability of secondary metabolite biosynthesis and can synthesize a variety of polypeptides and polyketones.The Region12 gene cluster is similar to the acidic,cyclic lipodepsi-peptide antibiotics biosynthesis gene cluster from Streptomyces fradiae.The core gene of Region12 was knocked out to verify the function of the gene and turned out to be silent gene.In addition,four compounds were isolated and purified from fermented broth of S10~T using various methods including solvent extraction,silica gel column chromatography,TLC,HPLC and so on.Compound 1-4-1 is a known product-differolide.Differolide could enhance the formation of aerial mycelium and spores of Streptomyces.Compound 3-4-1 has the ability to resist both Gram-positive and Gram-negative bacteria,and its structure is to be identified.The paper suggest that S10~T has a strong potential of secondary metabolic synthesis.The preliminary study on the separation and biosynthesis of S10~T natural products provides a theoretical basis for new active natural products and drug development.