Biomedical and Pharmaceutical Sciences
Pseudoalteromonas; alterochromides; probiotics; marine natural products; secondary metabolite
Pseudoalteromonas is a genus of ubiquitous Gram-negative marine bacteria known to produce a diverse array of bioactive secondary metabolites. Pseudoalteromonas piscicida JC3 is a probiotic strain discovered at the University of Rhode Island that has been shown to protect shrimp from fatal infections caused by pathogenic Vibrio parahaemolyticus. However, the mechanism for this host protection is currently unknown. We hypothesized that the JC3 strain secretes antimicrobial compounds that limit infections by the Vibrio. Genomic analysis of JC3 suggested that its biosynthetic potential to produce secondary metabolites known as alterochromides. Alterochromides and the related brominated derivatives bromoalterochromides are highly conjugated, cyclic chromopeptides that have been shown to exert cytotoxic effects. Recently, these secondary metabolites have also been linked with biofilm formation. To investigate the production of alterochromides by JC3, 24-hour cultures of P. piscicida were extracted by solvent partitioning with ethyl acetate then further separated via high-performance liquid chromatography (HPLC) using UV detection at 350 nm. Purified compounds were analyzed using liquid chromatography mass spectrometry (LCMS) and nuclear magnetic resonance (NMR) spectroscopy. Two alterochromides were isolated from the JC3 cultures and will be studied for their antimicrobial effects against V. parahaemolyticus. These findings lay the groundwork between linking secondary metabolite production and the probiotic activity of P. piscicida JC3.