Biosynthesis, Transcriptional Modulation, and Antibiotic Antidote Effect of Pseudovibriamides

Pseudovibrio α-Proteobacteria, frequently isolated from marine sponges, are hypothesized to benefit their hosts. A highly conserved hybrid nonribosomal peptide synthetase (NRPS)-polyketide synthase (PKS) gene cluster in Pseudovibrio spp., termed the ppp biosynthetic gene cluster (BGC), encodes the production of pseudovibriamides. Using reverse genetics and genetic complementation, we assigned functions to specific biosynthetic genes and defined the boundaries of the ppp BGC. Pseudovibriamide A is a linear heptapeptide and pseudovibriamide B is a nonadepsipeptide derived from pseudovibriamide A and pseudovibriamide C. Then, we report roles of pseudovibriamides in Pseudovibrio brasiliensis Ab134. We tested the hypothesis that pseudovibriamides modulate bacterial motility by influencing gene transcription. RNA-seq analysis of strains producing different pseudovibriamide compositions indicated that pseudovibriamides A and B regulate genes beyond those associated with motility, with pseudovibriamide B primarily promoting gene activation and pseudovibriamide A exerting inhibitory effects. This interplay suggests a compensatory mechanism in strains producing only pseudovibriamide A, as these strains exhibit flagellar motility comparable to the wild type. A differentially expressed LuxR-family regulator may contribute to the motility and transcriptional differences observed between strains producing different pseudovibriamide compositions. Furthermore, we demonstrated that pseudovibriamides selectively antagonize the antibiotic blasticidin S, highlighting their potential as antibiotic antidotes. This work enhances the understanding of the ecological roles of pseudovibriamides and provides insights into the broader applications of marine microbial natural products.