Secondary Metabolites In Streptomyces Research Articles

A Perspective for Assembling SALP(Streptomyces Artificial Linear Plasmid): A Potential New Genetic Tool of Gene Manipulation System for Producing Bioactive Secondary Metabolites in Streptomyces

Genetic systems for combinatorial biosynthesis of bioactive products including antibiotic have been developed in Streptomyces genus. Several shuttle vectors, including circular plasmid, cosmid, BAC (Bacterial Artificial Chromosome)/PAC (P1-derived Artificial Chromosome) between E. coli-Streptomyces have been used for manipulation of Streptomyces gene cluster for producing bioactive chemicals. Usually normal circular plasmids can carry only 1–20 kb DNA size. Cosmids are able to carry 37 to 52 kb of DNA, it was reported that cosmids have been successfully used for construction of Streptomyces genome libraries to clone biosynthetic gene clusters [2-7]. Nonetheless, most biosynthetic gene clusters for natural products are larger than the average capacity of common cosmid vectors, thus, vectors with large capacity such as BAC or PAC have been used to construct E. coli-Streptomyces artificial chromosomes for heterologous production of secondary metabolites [8-14]. The DNA fragments insertion loading capacity for BAC/PAC is from 100 kb up to 100-300 kb in E. coli cell, the large capacity of BAC/ PAC allows the gene manipulation of complete biosynthesis gene cluster of secondary metabolites in bacteria E. coli cell. However, E coli is not an ideal host for heterologous gene overexpression and production of Streptomyces biosynthesis gene cluster due to its lower genomic GC content compare to Streptomyces’s. In addition, BAC capacity can be up to 100 kb and more, but the copy number usually is low. Therefore, a shutter capability for the vector to introduce BAC back to Streptomyces host is required for efficient production. Intergeneric conjugation is a major approach for manipulating DNA shuttered between Streptomyces and E. coli [11].

Efficient pyramidal arrangement of an ordered cosmid library: Rapid screening of genes of the tacrolimus-producer Streptomyces sp. ATCC 55098

A gene library is a useful tool for molecular biology studies, but the classical screening of multiple plates is laborious and time-consuming. Cosmid gene libraries are particularly well suited for isolation of large gene clusters encoding the biosynthetic pathways of secondary metabolites in Streptomyces. A gene library of the immunosuppressant tacrolimus-producer strain Streptomyces sp. ATCC 55098 was constructed in the SuperCos1 vector and 1656 clones were organized in an easy pyramidal arrangement system. This clustering method allows a dual efficient screening (PCR and in situ colony hybridization) of the gene library in a two-step method by using only one 96-well plate. The dual screening combines the advantages of both techniques, the swiftness of PCR and the robustness of colony hybridization.

Streptoketol A and B, New Secondary Metabolites with DNA-Binding Properties

The new natural products, streptoketol A (1) and B (2), were discovered by chemical screening as secondary metabolites of Streptomyces sp. (strain GT 051243). The absolute stereochemistry of 1 was deduced by Helmchen's method and CD spectroscopy. The streptoketols show DNA-binding properties which were observed with a recently developed method using thin-layer chromatography (bio-molecular-chemical screening).

Gabosines L, N and O: New Carba-Sugars fromStreptomyces with DNA-Binding Properties

In addition to the known gabosines A (4), B (5) and C (6), three new gabosines L (1), N (2) and O (3) were detected by chemical screening as secondary metabolites of Streptomyces (strains GT 041230, GT 051024 and S 1096). The constitutions of 1, 2 and 3 were established by spectroscopic techniques and derivatization reactions. The absolute stereochemistry of 1 and 2 was determined by Helmchen's method and has been verified in the case of gabosine N (2) by X-ray analysis. The DNA-binding properties of the gabosines were investigated and analyzed by binding studies using a recently developed thin-layer chromatography technique (bimolecular-chemical screening).

Metabolites of Streptomyces noursei. V. Relation of the production of cycloheximide and actiphenol to the production of fungicidin.

Production of cycloheximide and fungicidin by the producing strainStreptomyces noursei 52/152 was shown to be coupled. Cycloheximide added to the culture medium increased the production of fungicidin, addition of fungicidin caused an increase of the production of cycloheximide. Antibiotic compounds added were degraded in the course of cultivation approximately to the same amount as if produced in control cultures. Cycloheximide added to the culture medium was not transformed to actiphenol. It was suggested that the synthesis of secondary metabolites ofStreptomyces noursei is controlled by mechanisms analogous to repression or allosteric inhibition.