Discovery of Ureido-Containing Alteropeptilides and Intramolecular Cyclized Alteramides in <i>Pseudoalteromonas flavipulchra</i> S16 by Promoter Engineering of Cryptic Biosynthetic Gene Clusters

<i>Pseudoalteromonas</i> are abundant in the oceans and possess great potential in the synthesis of bioactive natural products. Although many secondary metabolite biosynthetic gene clusters have been identified from <i>Pseudoalteromonas</i> genomes, most of their products have not been characterized. In this study, endogenous constitutive promoters with high transcriptional activity were obtained from <i>Pseudoalteromonas flavipulchra</i> S16 through RNA-seq and a fluorescence assay of luciferase gene expression. Through <i>in situ</i> promoter replacement two silent biosynthetic gene clusters (BGCs) were successfully activated, leading to production of intramolecular cyclized alteramides and two novel ureido-containing linear peptides, alteropeptilides. This study provides a feasible approach for the activation of silent BGCs and the mining of novel compounds from marine bacteria.