Isolation, identification and bioactive metabolites property of the strain secreting violet-blue pigment

Abstract:

[Objective] In order to investigate microbial diversity of the Qinling-Daba region, collect microbial culture and metabolites aimed to screen for active compounds, and establish the collection database as a platform for sharing inform. [Methods] The microbial strains from different habitats were isolated by the different methods and identified by physiological, biochemical and morphological characteristics and 16S rRNA gene sequence analysation, while the microbial metabolites were prepared for screening for active compound by fermentation in shaker flasks, extraction with methanol. [Results] An actinomycete, named strain Str-4331, was isolated from a soil sample in the Qinling-Daba region. It produced grayish-white aerial mycelium and solvable-violet-blue pigment on Gause’s synthetic agar, microscopic observation revealed that it produced helically spore hypha, the spores were elliptic to oblong. It was primarily identified as genus Streptomyces according to its morphological, physiological and biochemical characteristics. The 16S rRNA sequence of strain Str-4331 was analyzed by ClustalX, the phylogenetic tree was derived with NJ and analyzed with bootstrapping. The results showed that the 16S rRNA gene sequence of the strain Str-4331 shared the highest identity (99%) with that of S. lateritius strain: LMG 19372. The antibacterial activity of the extracted metabolites was determined and the results showed that the metabolites had the activity against the Gram-positive bacteria. The aqueous solution containing the metabolites showed different colors under different pH conditions. Liquid chromatography-mass spectroscopy analysation showed that the metabolites produced by the strain Str-4331 composed of three main compounds with the molecular weight separately 557.68 kD, 588.43?kD, 485.18 kD, while the molecular weight of granaticin B was 558 kD according to the documents. [Conclusion] The strain Str-4331 was identified as S. lateritiu from its morphological and cultural characteristics and the 16S rRNA gene sequence. This is the first report that S. lateritius strain was isolated in the Qinling-Daba region, and this study provided basis for the further exploration of the strain.