Exploring the specialized metabolome of the plant pathogen Streptomyces sp. 11-1-2

Streptomyces bacteria are notable for producing chemically diverse specialized metabolites that exhibit various bioactivities and mediate interactions with different organisms. Streptomyces sp. 11-1-2 is a plant pathogen that produces nigericin and geldanamycin, both of which display toxic effects against various plants. Here, the 'One Strain Many Compounds' approach was used to characterize the metabolic potential of Streptomyces sp. 11-1-2. Organic extracts were prepared from 11-1-2 cultures grown on six different agar media, and the extracts were tested in antimicrobial and plant bioassays and were subjected to untargeted metabolomics and molecular networking. Most extracts displayed strong bioactivity against Gram-positive bacteria and yeast, and they exhibited phytotoxic activity against potato tuber tissue and radish seedlings. Several known specialized metabolites, including musacin D, galbonolide B, guanidylfungin A, meridamycins and elaiophylin, were predicted to be present in the extracts along with closely related compounds with unknown structure and bioactivity. Targeted detection confirmed the presence of elaiophylin in the extracts, and bioassays using pure elaiophylin revealed that it enhances the phytotoxic effects of geldanamycin and nigericin on potato tuber tissue. Overall, this study reveals novel insights into the specialized metabolites that may mediate interactions between Streptomyces sp. 11-1-2 and other bacteria and eukaryotic organisms.

Revealing Genome-Based Biosynthetic Potential of Streptomyces sp. BR123 Isolated from Sunflower Rhizosphere with Broad Spectrum Antimicrobial Activity

Actinomycetes, most notably the genus Streptomyces, have great importance due to their role in the discovery of new natural products, especially for finding antimicrobial secondary metabolites that are useful in the medicinal science and biotechnology industries. In the current study, a genome-based evaluation of Streptomyces sp. isolate BR123 was analyzed to determine its biosynthetic potential, based on its in vitro antimicrobial activity against a broad range of microbial pathogens, including gram-positive and gram-negative bacteria and fungi. A draft genome sequence of 8.15 Mb of Streptomyces sp. isolate BR123 was attained, containing a GC content of 72.63% and 8103 protein coding genes. Many antimicrobial, antiparasitic, and anticancerous compounds were detected by the presence of multiple biosynthetic gene clusters, which was predicted by in silico analysis. A novel metabolite with a molecular mass of 1271.7773 in positive ion mode was detected through a high-performance liquid chromatography linked with mass spectrometry (HPLC-MS) analysis. In addition, another compound, meridamycin, was also identified through a HPLC-MS analysis. The current study reveals the biosynthetic potential of Streptomyces sp. isolate BR123, with respect to the synthesis of bioactive secondary metabolites through genomic and spectrometric analysis. Moreover, the comparative genome study compared the isolate BR123 with other Streptomyces strains, which may expand the knowledge concerning the mechanism involved in novel antimicrobial metabolite synthesis.

Targeted Discovery of the Polyene Macrolide Hexacosalactone A from Streptomyces by Reporter-Guided Selection of Fermentation Media

New approaches are still needed to fully explore the biosynthetic potential of microbes. We recently devised a melC reporter-guided fermentation media screening approach for targeted activation of cryptic gene clusters. Using this approach, we successfully activated the expression of the hcl gene cluster in Streptomyces sp. LZ35 and discovered a novel polyene macrolide hexacosalactone A (1).

Isolation and Identification of Secondary Metabolites FromStreptomycessp. SP301

Seven compounds, namely aminobenzoates A to D (1-4), naphthalenecarboxylates A and B (5-6), and glycosylatelactone A (7), were isolated from the fermentation medium of Streptomyces sp. SP301. Of these, aminobenzoates C and D (3-4), naphthalenecarboxylate B (6), and glycosylatelactone A (7) are new compounds. Aminobenzoates A to D (1-4) shared a common aromatic starter unit, para-aminobenzoic acid , and biosynthesis involving a different pathway. The structures were elucidated on the basis of 1D- and 2D-Nuclear Magnetic Resonance (NMR) spectroscopy and HR-ESIMS analysis.