Discovery and Biosynthesis of the Amodesmycins, Aromatic Polyketide-Siderophore Hybrid Conjugates.

A type II polyketide synthase biosynthetic gene cluster (amd) containing three P450 genes was identified from a soil metagenomic library, and novel benz[h]isoquinoline-desferrioxamine B conjugated compound amodesmycins were isolated from Streptomyces albus J1074 harboring the amd gene cluster. Genetic evidence showed that the benz[h]isoquinoline part and desferrioxamine B part in amodesmycins were derived from the amd gene cluster and S. albus J1074, respectively, while P450 enzymes played critical roles in the conjunction of these two parts.

Biosynthesis of coelulatin for the methylation of anthraquinone featuring HemN-like radical S-adenosyl-L-methionine enzyme.

Bacterial aromatic polyketides are usually biosynthesized by the type II polyketide synthase (PKS-II) system. Advances in deoxyribonucleic acid (DNA) sequencing, informatics, and biotechnologies have broadened opportunities for the discovery of aromatic polyketides. Meanwhile, metagenomics is a biotechnology that has been considered as a promising approach for the discovery of novel natural products from uncultured bacteria. Here, we cloned a type II polyketide biosynthetic gene cluster (BGC) from the soil metagenome, and the heterologous expression of this gene cluster in Streptomyces coelicolor M1146 resulted in the production of three anthraquinones, two of which (coelulatins 2 and 3) had special hydroxymethyl and methyloxymethyl modifications at C2 of the polyketide scaffold. Gene deletion and in vitro biochemical characterization indicated that the HemN-like radical S-adenosyl-L-methionine (SAM) enzyme CoeI exhibits methylation and is involved in C2 modification.

Regulated Expression of an Environmental DNA-Derived Type II Polyketide Gene Cluster in Streptomyces Hosts Identified a New Tetracenomycin Derivative TCM Y.

As bacterial natural products have been proved to be the most important source of many therapeutic medicines, the need to discover novel natural products becomes extremely urgent. Despite the fact that the majority of bacterial species are yet to be cultured in a laboratory setting, and that most of the bacterial natural product biosynthetic genes are silent, "metagenomics technology" offers a solution to help clone natural product biosynthetic genes from environmental samples, and genetic engineering enables the silent biosynthetic genes to be activated. In this work, a type II polyketide biosynthetic gene cluster was identified from a soil metagenomic library and was activated by over-expression of a SARP regulator gene in the gene cluster in Streptomyces hosts. A new tetracenomycin type compound tetracenomycin Y was identified from the fermentation broth. This study shows that metagenomics and genetic engineering could be combined to provide access to new natural metabolites.

Identification and characterization of a novel endo-ß-1,4-glucanase from a soil metagenomic library.

A cosmid clone cZFYN1413 with CMCase activity was identified from a soil metagenomic library. The sequence analysis of a subclone of cZFYN1413 revealed an endo-ß-1,4-glucanase gene ZFYN1413 belonging to glycoside hydrolase family 6 and a transmembrane region in the N-terminal of ZFYN1413. Expression of ZFYN1413 in Escherichia coli BL21 (DE3) resulted in ZFYN1413-87, which was a truncated protein cleaved in transmembrane region of ZFYN1413. ZFYN1413-87 was expressed and its enzyme properties were studied. ZFYN1413-87 possessed strong endo-ß-1,4-glucanase activity, and 52% of the activity could be retained after the protein was treated in buffer of pH 3.0 for 2 h. The study provided a special example of endo-ß-1,4-glucanase in GH6 family.