Characterization of Prodiginine Biosynthetic Pathway in Pseudoalteromonas rubra PPB1 Isolated from Petrosia Species

Abstract

Marine sponges (Porifera) play an ecologically important role in the coral reef ecosystem, providing diversity, biomass, primary production, and nitrification. Many sponges have been known to host biologically active microorganisms within their tissue system. These harboring microorganisms produce bioactive secondary metabolites, particularly pigments, that can benefit the sponge host. Marine sponge tissue samples were collected from Puhi Bay off the Eastern shore of Hilo, Hawai‘i. The sponge was identified as Petrosia sp. and possessed red pigmentation. Harboring microorganisms were isolated via surface sterilization and aseptic plating of sponge tissue samples. One isolate (PPB1) produced a colony with red pigmentation like that of Petrosia sp. Through 16S characterization, the isolate grouped within the Pseudoalteromonas genus. Biological assays of Pseudoalteromonas sp. PPB1 crude extract demonstrated both antimicrobial and antioxidant activity. To determine the potential metabolites that contribute to both the red pigmentation and biological activity, the draft genome was sequenced, assembled, and annotated. The genome revealed a prodiginine biosynthetic pathway and the first cited-incidence of a prodiginine-producing Pseudoalteromonas species harboring within a marine sponge host. This study aims to: (i) understand the biological activity of prodiginine derivatives, (ii) characterize gene clusters involved in prodiginine and other secondary metabolite biosynthesis, and (iii) determine factors that influence prodiginine biosynthesis gene expression. Further understanding of the bioactivity, biosynthesis, and regulation of secondary metabolites like prodiginine may uncover the ecological interactions between host sponge and microorganism.