Genome mining reveals the origin of a bald phenotype and a cryptic nucleocidin gene cluster in Streptomyces asterosporus DSM 41452.

Streptomyces asterosporus DSM 41452 is a producer of the polyketide annimycin and the non-ribosomal depsipeptide WS9326A. This strain is also notable for exhibiting a bald phenotype that is devoid of spores and aerial mycelium when grown on solid media. Based on the similarity of the 16S rRNA sequence to Streptomyces calvus, the only known producer of the fluorometabolite nucleocidin, the genome of S. asterosporus DSM 41452 was sequenced and analyzed. Twenty-nine natural product gene clusters were detected in the genome, including a gene cluster predicted to encode the fluorometabolite nucleocidin. Through genome analysis and gene complementation experiments, we demonstrate that the bald phenotype arises from a transposon gene inserted within the promoter sequence for the pleiotropic regulator adpA. Complementation of S. asterosporus DSM 41452 with a functional adpA sequence restored morphological differentiation and promoted the production of nucleocidin.

SeMPI: a genome-based secondary metabolite prediction and identification web server.

The secondary metabolism of bacteria, fungi and plants yields a vast number of bioactive substances. The constantly increasing amount of published genomic data provides the opportunity for an efficient identification of gene clusters by genome mining. Conversely, for many natural products with resolved structures, the encoding gene clusters have not been identified yet. Even though genome mining tools have become significantly more efficient in the identification of biosynthetic gene clusters, structural elucidation of the actual secondary metabolite is still challenging, especially due to as yet unpredictable post-modifications. Here, we introduce SeMPI, a web server providing a prediction and identification pipeline for natural products synthesized by polyketide synthases of type I modular. In order to limit the possible structures of PKS products and to include putative tailoring reactions, a structural comparison with annotated natural products was introduced. Furthermore, a benchmark was designed based on 40 gene clusters with annotated PKS products. The web server of the pipeline (SeMPI) is freely available at: http://www.pharmaceutical-bioinformatics.de/sempi.

StreptomeDB 2.0--an extended resource of natural products produced by streptomycetes.

Over the last decades, the genus Streptomyces has stirred huge interest in the scientific community as a source of bioactive compounds. The majority of all known antibiotics is isolated from these bacterial strains, as well as a variety of other drugs such as antitumor agents, immunosuppressants and antifungals. To the best of our knowledge, StreptomeDB was the first database focusing on compounds produced by streptomycetes. The new version presented herein represents a major step forward: its content has been increased to over 4000 compounds and more than 2500 host organisms. In addition, we have extended the background information and included hundreds of new manually curated references to literature. The latest update features a unique scaffold-based navigation system, which enables the exploration of the chemical diversity of StreptomeDB on a structural basis. We have included a phylogenetic tree, based on 16S rRNA sequences, which comprises more than two-thirds of the included host organisms. It enables visualizing the frequency, appearance, and persistence of compounds and scaffolds in an evolutionary context. Additionally, we have included predicted MS- and NMR-spectra of thousands of compounds for assignment of experimental data. The database is freely accessible via http://www.pharmaceutical-bioinformatics.org/streptomedb.

Metabolic pathway monitoring of phenalinolactone biosynthesis from Streptomyces sp. Tü6071 by liquid chromatography/mass spectrometry coupling.

RATIONALE: A rapid and precise analytical method for the investigation of natural products is required for pathway monitoring of the biosynthesis of secondary metabolites. Phenalinolactones, used in antibiotic research, are produced by Streptomyces sp. Tü6071. For the analysis of those compounds, prior to mass spectrometric analysis, an efficient separation technique is required. METHODS: For the identification of phenalinolactones from liquid cultures of Streptomyces sp. Tü6071, a new method comprising the combination of solid-phase extraction (SPE) prior to liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) was established. MS/MS product ion scans were applied for phenalinolactone detection and structure elucidation, performed in negative mode and optimized for sensitivity and specificity. For the discovery of new intermediates, a MS/MS precursor ion scan was applied. RESULTS: Analysis of the extracts revealed that the Oasis® MAX cartridge, containing a quaternary amine functionality, is the most efficient SPE material for purification of phenalinolactones, since it allowed sufficient enrichment and detection of intermediates from the biosynthetic pathway by LC/ESI-MS/MS. Using the precursor ion scan technique, two new secondary metabolites, PL IM1 with m/z 672.6 and PL IM2 with m/z 433.3, have been detected. The structures of the new intermediates are postulated and arranged into the biosynthetic pathway of phenalinolactones. CONCLUSIONS: A precise analytical method was established for the identification of phenalinolactones by combining purification from Streptomyces using SPE prior to LC/ESI-MS/MS. By optimising LC/ESI-MS/MS settings, this method has been successfully applied for pathway monitoring of secondary metabolites. Application of a precursor ion scan allowed for the identification of unknown intermediates in biosynthetic pathways.