Studies On Isolation, Identification And Agricultural Activity Of Symbiotic Or Epiphytic Actinomycetes From Marine Fish

The oceans cover more than 70% of the earth's surface, and little is known about the symbiotic or epiphyte actinomycetes of marine fish. As an important group of marine ecological environment, the marine fish contain limited amounts of marine microorganism community. The marine fish symbiotic or epiphyte actinomycetes will become a remarkably prolific source of structurally diverse secondary metabolites, including many that possess pharmaceutically relevant biological activities.To better understand the actinomycetes diversity associate with marine fish, we attempted to isolate and cultivate actinomycets from the marine fish collected from Pingtan sea area in Fuzhou city for further physiological studies and to explore natural products. We selected 7 kinds of different actinomycetes isolation media and the results showed that the nutrient-poor media, in addition to suitable inhibitors, could yield more actinomycetes from marine fish. In this study 29 actinomycetes were isolated from marine fish.Biological activity testing of 29 actinomycetes revealed that 17 strains had activities against 4 plant pathogenic fungi strains such as Rhizoctonia cerealis. Evidence is also provided that the strain 030603 has strong anti-fungi activity. Further screening using the secondary metabolite production from strain 030603 fermentation products against 14 plant pathogenic fungi strains indicates that 030603 broadly inhibited plant pathogenic fungi. The medium inhibitory concentration(ECso) agianst Ophiclus graminis was 0.12 g/L and against Rhizoctonia cerealis was 0.36 g/L.Twentiy-nine marine symbiotic and epiphyte actinomycetes strains'crude extracts were tested against TMV and SGC-7901. The evidence show that 6 isolates were strong antagonists of TMV, and the inhibitory rates exceed 50%. Inaddition to strain 042403 which isolated from Acanthopagrus schlegel strongly inhibited growth of gastric cancer SGC-7901.12. The fermentation broth crude extracts and mycelium crude extracts (500μg/mL) inhibitory rates were 96.5% and 99.5%. A combination of physiological parameters, chemotaxonomic characteristics, distinguishing 16S rDNA gene sequences, and the evidences show that the strains 010204,20101,030603 and 042403 were proposed as Streptomyces pseudogriseolus 010204, Streptomyces globisporus 020101, Streptomyces albidoflavus 030603, Streptomyces. hygroscopicus 042403, and 042403 was candidate for new specie.We modified the fermentation conditions on the production of strain 030603 fermentation products against Rhizoctonia cerealis. The optimum culture includes: glycerol 1.5%, peptone 3%, soluble starch 2%, soybean flour 1.5%. sea salt 0%. The optimum inoculation condition is:initial pH 5-7, seed cultural time 48 h,6% inoculation amount and 200 r/min for 120 h. Under the optimized conditions, the crude extracts(1 mg/mL) inhibitory rates against Rhizoctonia cerealis was 98.78%.