Phenotypic and Functional Diversity in Meat-Associated Pseudomonas Isolates: Motility, Biofilm Formation, and AI-2 Activity

Abstract

Pseudomonas species are important spoilage bacteria in aerobically stored chilled meat; however, the occurrence of the interspecies quorum sensing signal autoinducer-2 (AI-2) and its association with biofilm formation and motility in these bacteria remain insufficiently understood. In this study, Pseudomonas isolates obtained from spoiled beef steak and minced beef were characterized for biofilm formation, motility traits, and AI-2 activity. RpoD sequence analysis of the preselected Pseudomonas fragi-related isolates revealed a diverse species composition, with Pseudomonas bubulae being more frequently identified than P. fragi. This finding highlights the importance of updated taxonomic approaches for species-level identification within this group. Thirty-five isolates that were positive in the Congo red agar assay were evaluated for biofilm formation at 4 °C and 25 °C over 7 days. Mean biofilm formation was significantly higher at 25 °C during early incubation, whereas prolonged incubation resulted in comparable biofilm levels under chilled conditions. AI-2 activity was detected in 25 isolates using a Vibrio campbellii bioluminescence assay. Principal component analysis showed that AI-2-like activity and biofilm formation contributed to a similar phenotypic dimension, whereas direct Spearman correlation analysis revealed no significant monotonic relationship between these traits. Overall, these findings highlight the phenotypic versatility of meat-associated Pseudomonas spp. and suggest that biofilm formation is likely influenced by multiple strain-specific and environmental factors beyond AI-2-like activity.