| With the antibacterial activity of secondary metabolites produced by sponge-associated actinobacteria on mariculture pathogenic vibrio as the study purposes,27 strains were isolated from Reniochalina sp.,Mycale sp.and Suberites domuncula.59 strains after removing duplicate with strains early saved in the laboratory were preliminary identifyied as Streptomyces by analyzing the sequence of 16 S r DNA,and their antibacterial activity were screened together with4 starins of gram-negative bacteria(Vibrio parahaemolyticus,Vibrio harveyi,Vibrio anguillarum,Vibro Splendidus)and 2 starins of gram-positive bacteria(Streptococcus iniae,Staphylococcus equorum)as indicator.11 strains with strong antibacterial activity and broad spectrum were screened out with repeatedly screening,and FH starin was finally determined for research.The study of antibacterial activity of FH starin with Vibrio parahaemolyticus and Vibrio harveyi as indicator were as follows.The sponge-associated actinobacteria FH was preliminary identifyied as Streptomyces globisporus by analyzing the sequence of 16 S r DNA.Fermentation conditions of FH starin were optimized with antibacterial activity oriented.The optimization results were temperature 25℃,p H 7.5,loading volume 30 m L / 250 m L,fermentation time 120 h.The character study of FH strain showed that the crude extracts from fermented liquid of FH strain was equivalent to the titer of 387.27 mg/L gentamycin standard liquid and was stable preserved at 4℃ and-20℃ in 2months.The vibrios of experimental group adding fermentation products of FH strain were effectively inhibited or even killed in sterile sea water with the initial density of Vibrio parahaemolyticus and Vibrio harveyi as 103 cfu/ m L.The vibrios of experimental group adding mycelia of FH strain were effectively suppressed in sterile sea water with the initial density of Vibrio parahaemolyticus as 103 cfu/ m L and the initial density of Vibrio harveyi as 102 cfu/m L.In the sea cucumber seedling,the mycelia of FH strain showed good results in vibriosis prevention indicating it was feasible as a means of biological control,but the fermentation products and crude extracts from fermented liquid of FH strain were not suitable to add in the aquaculture water directly as prevention or therapy method.The research of antibacterial activity of FH strain and its fermentation product illustrated that sponge-associated actinobacteria had good development potential in natural active products and a broad prospect in mariculture. |
