Genome-directed discovery of antiproliferative bafilomycins from a deepsea-derived Streptomyces samsunensis

Exploring the bioactive potential of deep-sea microorganisms: A review of recent discoveries

The deep-sea ecosystem, one of the most extreme and underexplored environments, harbors a remarkable diversity of microorganisms capable of producing bioactive compounds with immense pharmaceutical potential. Deep-sea microorganisms, inhabiting depths beyond 100 m, have emerged as a particularly promising source of novel bioactive compounds due to their adaptation to extreme conditions such as high pressure, low temperatures, and absence of light. This review highlights recent advancements in the discovery and characterization of 440 novel natural products from deep-sea organisms (100-11,000 m) between 2020 and October 2024. It encompasses a diverse range of deep-sea fungi and actinomycetes, detailing their source organisms, collection depths, and geographic origins. Remarkably, 80 % of these compounds exhibit bioactivity, with nearly half demonstrating potent cytotoxicity at low micromolar concentrations against various human cancer cell lines. Despite the vast majority of deep-sea microbes remaining unexplored, their potential to yield unique natural products is immense. This review succinctly presents these discoveries, emphasizing their potential biological applications and underscoring the deep-sea as a frontier for future pharmaceutical research.

Genome-guided discovery of two undescribed 6,6-spiroketal polyketides and stereochemical correction of bafilomycins P and Q from the marine-derived Streptomyces sp. SCSIO 66814

Bafilomycins are macrocyclic polyketides with intriguing structures and therapeutic value. Genomic analysis of Streptomyces sp. SCSIO 66814 revealed a type I polyketide synthase biosynthetic gene cluster (BGC), namely blm, which encoded bafilomycins and featured rich post-modification genes. The One strain many compounds (OSMAC) strategy led to the discovery of six compounds related to the blm BGC from the strain, including two previously undescribed 6,6-spiroketal polyketides, streptospirodienoic acids D (1) and E (2), and four known bafilomycins, bafilomycins P (3), Q (4), D (5), and G (6). The structures of 1 and 2 were determined by extensive spectroscopic analysis, quantum calculation, and biosynthetic analysis. Additionally, the absolute configurations of the 6/5/5 tricyclic ring moiety containing six consecutive chiral carbons in the putative structures of 3 and 4 were corrected through NOE analysis, DP4+ calculation, and single-crystal X-ray diffraction data. Bioinformatic analysis uncovered a plausible biosynthetic pathway for compounds 1-6, indicating that both streptospirodienoic acids and bafilomycins were derived from the same blm BGC. Additionally, sequence analysis revealed that the KR domains of module 2 from blm BGC was B1-type, further supporting the configurations of 1-4. Notably, compounds 3 and 4 displayed significant cytotoxic activities against A-549 human non-small cell lung cancer cells and HCT-116 human colon cancer cells.