Research On Two Marine Algicidal Microorganisms And Their Secondary Metabolites

It is a worldwide project to prevent and control the harmful algal blooms(HABs).It has been proved that there has a special symbiotic system between microalgae and microorganisms in the marine symbiotic system.Small molecules play an important role in the symbiotic system.Among them,marine algae-killing microbials and algicidal components have attracted sustained attention.It is one of the most potential biological approaches to control HABs by algae-killing microbials and algicidal components in the future.As part of the screening of algicidal components in this study,20 strains of marine microorganisms from Dapeng Peninsula in Shenzhen were selected,including 11 bacterial,4 fungi and 5 actinomycete strains.In addition,7 strains of marine fungi from Yongxing Island were also used for this study.The secondary metabolites were extracted from the above 27 strain safter liquid fermentation.14isolates exhibited algicidal activities against red tide causing algae,Akashiwa sanguine.Among them,4 strains,HKB017,F2-2(Streptomyces sp.),Pte-L059-1,and Bzo-L062-2(Myrothecium sp.),exhibited the strongest activities at 100?g·m L^-1(inhibition rate?90%).Myrothecium sp.Bzo-L062-2 and Streptomyces sp.F2-2 were selected for fermentation amplification.The secondary metabolites from the Bzo-L062-2 and F2-2were extracted and separated by organic solvent extraction and modern chromatographic methods,such as silica gel column chromatography,Sephadex LH-20,ODS column chromatography and high performance liquid chromatography,etc.The structures were elucidated on the basis of their spectroscopic and physico-chemical properties.Fifteen compounds were purified and eleven compounds were characterized from Myrothecium sp.Bzo-L062-2,including Myrothspiroxepine(1),2,6,8-Trihydroxy-3,7-dimethylnaphthalene-1,4-dione(2),Aspergiodiquinone(3),2,7-Dihydroxy-6-(1-hydroxyethyl)-3-methylnaphthalene-1,4-dione(4),Terreinol(5),2-Hydroxy-6-methylbenzoic acid(6),P-methylbenzenesulfonamide(7),4-Hydroxybenzoic acid(8),5-hydroxymethyl-2-furoic acid(9),5-Hydroxymethylfuran-2-carboxylate(10),3,4-Dihydroxy-benzoic acid(11);Two compounds were obtained from Streptomyces sp.F2-2,including Actinomycin D(12)and Actinomycin X2(13).Compounds 1 and compound 2 were new compounds.4-Hydroxybenzoic acid(8),5-hydroxymethyl-2-furoic acid(9),5-Hydroxymethylfuran-2-carboxylate(10),Actinomycin D(12),Actinomycin X2(13)were tested against the red tide algae Chattonella marina,however,so far there has no compounds showed significant activities.Futher screening works are ongoing in the lab.