Study On The Effect Of Co-culture On The Characteristics Of Streptomyces MY02 And Its Inducers

Streptomyces rimosus MY02 was isolated from a soil sample which was collected from the northeast of China.The liquid broth of S.rimosus MY02 could partially inhibited Gram-positive and Gram-negative bacteria,also most fungi.Rimocidin produced by S.rimosus MY02 is a kind of polyene antibiotic,which has important application in medicine and agriculture.In this work,co-culture systems were built to improve the production of rimocidn producing by S.rimosus MY02 and try to explore the inductive mechanism of the co-culture system.The other inductive properties of S.rimosus MY02 were analysised;the influence of activity caused by inductive strains to other Streptomyces was also researched.In this research,70 strains maintained in the lab were used as inductive strains,including 52 strains of bacteria,6 strains of actinomyces and 12 strains of fungi.70 groups of co-culture systems were built with S.rimosus MY02 and inductive strains.After co-culture,the yield of Rimocidin was evaluated and the inductivity of each inductive srtains was calculated.The strains which had significant influence to MY02 were screened:there were fungal inductive strain 3.4261 and bacteria 1.0941.The relations between the growth rate of fungal hyphae and fungal inductivity,the pH of 3.4261 fermentation broth and the yield of Rimocidin were researched.The co-culture condition of 3.4261 and MY02 in shake flask was optimized to get high-yield Rimocidin.The optimal conditions:the inoculation time of 3.4261 was after MY02 fermentation 36 h,the inoculation amount of 3.4261 was 2%,the cell age of 3.4261 was 4 d.Compared with pure-culture MY02,the Rimocidin of MY02 which co-cultured with 3.4261 could increase by 70%.The inductive mechanism of this co-culture system was explored.The results showed us that the elicitor existed in the 3.4261 fermentation broth.Ethyl acetate was used to extract the supernatant of ethanol precipitation which was from 3.4261 fermentation broth,the residual aqueous has significant inductive effect.The optimal inoculation time and inoculation amount of elicitor were 24 h and 10-20%,respectively.Red pigment could be observed when MY02 co-cultured with bacteria inductive strain 1.0941.Further analysis of the water-soluble red pigment was done.The analysis results of UV-visible absorption spectroscopy,liquid chromatography-mass spectrometry and nuclear magnetic resonance showed that:the absorption wavelength was 558nm,molecular weight was about 588.Infrared spectroscopy showed that the molecular structure of the red pigment comtained amino group and carboxyl group.Nuclear magnetic resonance spectroscopy showed that the structure of the red pigment contained benzene ring.Three strains which had higher inductivity were used to co-cultue with 18 other Streptomyces.The results showed different Streptomyces had different fit inductive strains;the same inductive strain had different inductive effects to different Streptomyces.We could find out co-colture could enhance the inhibition activity of Streptomyces.This research laid a foundation for the mechanism of co-culture system.Furthermore,the work in the research also provided proof for new compound in co-culture.It makes the expanded practical application of co-culture become a guide.