“Pinkalicious": Outer Membrane Vesicles Isolated from Pseudoalteromonas rubra Carry Prodigiosin Antibiotics as Cargo

Author(s)

Margaret HillFollow

Major

Pharmaceutical Sciences

Minor(s)

Biology

Advisor

Rowley, David, C

Advisor Department

Biomedical and Pharmaceutical Sciences

Date

5-2023

Keywords

Pseudoalteromonas rubra; Probiotics; Prodigiosin; Prodiginines; Astrangia poculata

Abstract

Astrangia poculata, the state coral of Rhode Island, is susceptible to infection by Vibrio coralliilyticus RE22, which is a common marine pathogen affecting various invertebrate species. The settlement of coral larvae prior to the establishment of colonies is mediated by crustose coralline algae (CCA). This process may be induced by CCA-associated protective bacteria that colonize corals in early metamorphosis; furthermore, such bacteria potentially have downstream effects in the susceptibility of corals to pathogens. Strains of Pseudoalteromonas rubra isolated from CCA have been shown to induce larval settlement of tropical corals. We hypothesize that P. rubra induces the settlement of A. poculata larvae by producing specialized metabolites packaged within outer membrane vesicles (OMVs). Prodiginines are a class of red-pigmented secondary metabolites that were first isolated from Serratia marcescens, and subsequently identified in extracts of various Pseudoalteromonas species including our putative probiotic of interest, P. rubra. Prodiginines have a broad spectrum of biological activities, such as antimicrobial and algicidal activity, toxigenicity, and immunosuppressive properties; furthermore, their ability to affect biofilm production also hint at their potential role in quorum sensing. P. rubra OMVs would likely select for cargoes that exhibit antagonism towards competing (pathogenic) strains. We have identified such prodiginines, namely prodigiosin and 2-methyl-3-hexyl prodiginine, in extracted supernatants, as well as isolated OMVs of P. rubra strains KB1 and CH007. The future directions of this project will include further characterization and eventual quantification of P. rubra OMVs, with the intention of focusing on the prodiginine analogues as cargo.