Adaptive responses of Pseudomonas marginalis to modified atmosphere packaging conditions

Postharvest bacterial infections pose a significant threat to fruit and vegetable quality and safety, particularly due to pathogens' adaptive responses to storage conditions. This study utilized morphological and multi-omics approaches to investigate Pseudomonas marginalis survival and tomato soft rot progression under modified atmosphere packaging (MAP) conditions. Our findings indicate that MAP (initial 21 % O₂, 0 % CO₂, transitioning to 1 % O₂, 20 % CO₂ over 48 h) supported colony growth (12 ± 0.5 mm) comparable to air, whereas rapid shift to controlled atmosphere (1 % O₂, 20 % CO₂) markedly suppressed growth (10 ± 0.5 mm) and caused membrane disruption, consistent with the highest proportion of PI-positive cells (24.3 ± 2.7 %) after 2 days. In contrast, MAP maintained moderate viability (17.8 ± 2.0 %), indicating enhanced adaptive response. Transcriptomic and metabolomic analyses revealed that MAP gases influenced bacterial responses, specifically modulating two-component system (TCS) and ATP-binding cassette (ABC) transporter pathways crucial for adaptation. MAP decreased the expression of genes associated with multi-step phosphorelay signaling (fecl, pfeS, cheV, narL, vicR, spo0F) and glutamine signaling (potF, pstS), and altered iron homeostasis-related genes (fecl, fecR, pvdE). Metabolomics profiling showed elevated levels of L-type amino acids (LAA) and fumaric acids, with reduced D- (+)- Glucose. Transcriptomic patterns were validated by RT-qPCR with strong correlations (R² = 0.83). In conclusion, MAP facilitates P. marginalis adaptation and soft rot development by modulating key stress and metabolic pathways. These findings provide a foundation for refining MAP strategies, suggesting rapid shifts to microaerobic conditions of controlled atmosphere or active O₂ scavenging to mitigate P. marginalis-induced postharvest losses.