Functional genomic characterization reveals the probiotic tendency and safety assessment of Exiguobacterium acetylicum G1-33 isolated from the gut of the hybrid grouper ( Epinephelus fuscoguttatus ♀ x E. lanceolatus ♂)

Probiotics are commonly used as nutritional supplements and antibiotic substitutes and thus are of great commercial interest. The present study was performed to demonstrate the probiotic potential of Exiguobacterium acetylicum G1-33 isolated from the gut of the hybrid grouper ( Epinephelus fuscoguttatus female x E. lanceolatus male ) by integrating genomics and phenotypic traits. In silico genome analysis confirmed its identity as E. acetylicum . Functional annotation of the genome revealed the existence of molecular markers responsible for the functional properties of potential probiotics, such as resistance to the host's harsh gastrointestinal environment, adhesion and colonization of the intestinal mucosa, competition and inhibition of pathogens, responses to oxidative stress, and biosynthesis of essential amino acids and vitamins. The genomic analysis was validated by in vitro experiments. Effective toxin-encoding genes were not identified in the G1-33 genome, and the safety of the strain was confirmed by in vitro experiments. These results indicate that E. acetylicum G1-33 exhibits excellent probiotic properties and can become a probiotic with high application value in aquaculture.