Guillen-Matus, D. | bioRxiv Science

bioRxiv2024

Structure elucidation, biosynthetic gene cluster distribution, and biological activities of ketomemicin analogs in Salinispora

We report three new ketomemicin pseudopeptides (1-3) from extracts of the marine actinomycete Salinispora pacifica strain CNY-498. Their constitution and relative configuration were elucidated using NMR, mass spectrometry, and quantum chemical calculations. Using GNPS molecular networking and publicly available Salinispora LCMS datasets, five additional ketomemicin analogs (4-8) were identified with ketomemicin production detected broadly across Salinispora species. The ketomemicin biosynthetic gene cluster (ktm) is highly conserved in Salinispora, occurring in 79 of 118 public genome sequences including eight of the nine named species. Outside Salinispora, ktm homologs were detected in various genera of the phylum Actinomycetota that might encode novel ketomemicin analogs. Ketomemicins 1-3 were tested against a panel of eleven proteases, with 2 displaying moderate inhibitory activity. This study describes the first report of ketomemicin production by Salinispora cultures, the distribution of the corresponding biosynthetic gene cluster, and the protease inhibitory activity of new ketomemicin derivatives. Table of Content/Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=64 SRC="FIGDIR/small/620863v1_ufig1.gif" ALT="Figure 1"> View larger version (23K): org.highwire.dtl.DTLVardef@481b56org.highwire.dtl.DTLVardef@1fad340org.highwire.dtl.DTLVardef@433ffaorg.highwire.dtl.DTLVardef@11d5d33_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2020

Complex evolutionary dynamics govern the diversity and distribution of biosynthetic gene clusters and their encoded specialized metabolites

While specialized metabolites are thought to mediate ecological interactions, the evolutionary processes driving their diversification, particularly among closely related lineages, remain poorly understood. Here, we examine the evolutionary dynamics governing the distribution of natural product biosynthetic gene clusters (BGCs) using 118 strains within the marine actinomycete genus Salinispora. While previous evidence indicated that horizontal gene transfer (HGT) largely contributed to BGC diversity, we find that a majority of BGCs in Salinispora genomes are conserved through processes of vertical descent. In particular, vertical inheritance maintained BGCs over evolutionary timescales (millions of years) allowing for BGC diversification among Salinispora species. By coupling the genomic analyses with high-resolution tandem mass spectrometry (LC-MS/MS), we identified that BGC evolution in Salinispora proceeds largely through gene gain/loss events and constrained recombination that contributes to interspecies diversity at the gene, pathway, and metabolite levels. Consequently, the evolutionary processes driving BGC diversification had direct consequences for compound production and contributed to chemical diversification, as exemplified in our case study of the medically relevant proteosome inhibitors, the salinosporamides. Together, our results support the concept that specialized metabolites, and their cognate BGCs, represent functional traits associated with niche differentiation among Salinispora species. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=107 SRC="FIGDIR/small/423547v2_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@aef190org.highwire.dtl.DTLVardef@17536baorg.highwire.dtl.DTLVardef@5bf336org.highwire.dtl.DTLVardef@bc7d2f_HPS_FORMAT_FIGEXP M_FIG C_FIG O_TEXTBOXSIGNIFICANCENatural products are traditionally exploited for their pharmaceutical potential; yet what is often overlooked is that the evolution of the biosynthetic gene clusters (BGCs) encoding these small molecules likely affects the diversification of the produced compounds and implicitly has an impact on the compounds activities and ecological functions. And while the prevailing dogma in natural product research attributes frequent and widespread horizontal gene transfer (HGT) as an integral driver of BGC evolution, we find that the majority of BGC diversity derives from processes of vertical descent, with HGT events being rare. This understanding can facilitate informed biosynthetic predictions to identify novel natural products, in addition to uncovering how these specialized metabolites contribute to the environmental distribution of microbes. C_TEXTBOX

microbiology↗