Functional characterization of the recombinant L-type lectin from red alga
Gracilaria fisheri with antibacterial potential

Marine algal lectins are promising bioactive compounds with antimicrobial potential. This study produced and characterized a recombinant legume-type lectin from Gracilaria fisheri (rLGFL) and evaluated its antibacterial activity. The LGFL gene was cloned, sequence-verified, and expressed in Escherichia coli. Western blot analysis using a mouse polyclonal antiserum confirmed rLGFL expression. Functional assays demonstrated strong hemagglutination against rabbit erythrocytes, indicating carbohydrate recognition domain (CRD) functionality. rLGFL agglutinated Vibrio parahaemolyticus (3HP), Vibrio harveyi (1114), and Aeromonas veronii while exhibiting bactericidal activity against all tested pathogens, including non-agglutinated V. parahaemolyticus (A3212), Streptococcus agalactiae, Aeromonas hydrophila, and Edwardsiella ictaluri. These findings suggest dual antibacterial mechanisms: agglutination-mediated pathogen immobilization and direct bactericidal effects. Seasonal analysis of G. fisheri from Songkhla, Thailand, revealed peak LGFL expression from January to March and July to September, identifying optimal harvesting periods. This study highlights rLGFL as a potential eco-friendly antibacterial agent with applications in aquaculture and disease management.