Membrane Vesicle-Mediated Delivery of Antibacterial Lipopeptides by Pseudoalteromonas piscicida

Area of Science:

• Microbiology
• Natural Products Chemistry
• Biochemistry

Background:

• Bacterial membrane vesicles (MVs) are recognized carriers of biomolecules.
• The transport of lipophilic specialized metabolites via MVs is poorly understood.
• Aquatic microbial ecosystems rely on metabolite exchange, often involving poorly soluble compounds.

Purpose of the Study:

• To investigate the role of MVs in transporting lipophilic metabolites.
• To identify and characterize metabolites packaged into MVs by *Pseudoalteromonas piscicida* JC3.
• To assess the functional implications of MV-mediated metabolite delivery.

Main Methods:

• Untargeted metabolomics and molecular networking for metabolite identification.
• Targeted LC-MS/MS for metabolite localization within cells and MVs.
• Isolation, spectroscopic analysis (including modified Marfey's analysis) for structure elucidation.
• Functional assays to evaluate MV antibacterial activity.

Main Results:

• Bromoalterochromides (BACs), lipophilic depsipeptides, were identified within MVs of *P. piscicida* JC3.
• Six known and two novel BACs were discovered; BACs were localized to MVs and cells, not supernatants.
• A new analogue, bromoalterochromide E/E', was structurally elucidated.
• BAC-loaded MVs demonstrated antibacterial activity against *Staphylococcus aureus* and *Vibrio anguillarum*.

Conclusions:

• Bacterial membrane vesicles actively transport lipophilic specialized metabolites like BACs.
• MV-mediated delivery of BACs contributes to microbial competition in aquatic environments.
• These findings suggest MVs as potential natural drug delivery systems for therapeutic applications.