Phenotypic and Genomic Characterization of Paenibacillus polymyxa SABE1 as a Probiotic Candidate in European Sea Bass...

In the 21st century, the emergence of multidrug-resistant bacteria has become a major concern in human and animal health, promoting the search for sustainable alternatives to antibiotics in aquaculture. Among these, probiotics have shown promising potential to improve fish health and disease resistance. This study evaluates the probiotic potential of Paenibacillus polymyxa SABE1 for application in European seabass (Dicentrarchus labrax) aquaculture. Its functional properties were assessed through in vitro assays, a challenge test against Vibrio parahaemolyticus, and whole-genome sequencing to determine safety and potential risks. Results indicate that P. polymyxa SABE1 exhibits strong antimicrobial activity, adhesion capacity, digestive resilience, and no hemolytic or pathogenic traits. Notably, the challenge assay showed a survival rate of 56.67% in treated fish, confirming its protective effect. Genomic analysis further supported its safety, revealing no relevant antibiotic resistance or virulence factors. Overall, P. polymyxa SABE1 demonstrates strong potential as a safe and effective probiotic candidate, supporting its use as a sustainable alternative to antibiotics in aquaculture.