Assessment of metabolic changes in Acinetobacter johnsonii and Pseudomonas fluorescens co-culture from bigeye tuna (Thunnus obesus) spoilage by ultra-high-performance liquid chromatography-tandem mass spectrometry

Acinetobacter johnsonii and Pseudomonas fluorescens are specific spoilage microorganisms (SSO) of aquatic products, and their metabolites are effective indicators for analyzing these two SSOs. However, the metabolome of a coculture of A. johnsonii and P. fluorescens is still unclear. The aim of this study was to investigate the metabolomic changes in A. johnsonii, P. fluorescens, and their co-culture by screening for metabolic markers. PCA and PLS-DA revealed that A, P, and AP groups were different from each other, indicating a significantly varying metabolic profile among them. Based on UHPLC information, 540 metabolites with significant differences, were identified in the ESI+ and ESI- modes, which covered 79 metabolic pathways. The different metabolites were mainly related to the pathways, such as taurine and hypotaurine metabolism:M, bile secretion:OS, and arginine biosynthesis:M were in the A vs AP group, while PPAR signaling pathway:OS, tropane, piperidine, and pyridine alkaloid biosynthesis:M, longevity regulating pathway-worm:OS, choline metabolism in cancer:HD, biosynthesis of phenylpropanoids:M, and amoebiasis:HD were in the P vs AP group. Therefore, this study may provide significant information regarding the metabolic mechanisms of A. johnsonii, P. fluorescens, and their co-cultures, which may provide insights on their role in deteriorating the quality of aquatic products.