Antimicrobial activities and phylogenetic study of Erythrina senegalensis DC (Fabaceae) seed lectin

Erythrina senegalensis (Fabaceae) have been traditionally used in the treatment of microbial ailments, and the specific agent mediating its efficacy has been investigated in several studies. In this study, the antimicrobial activity of purified E. senegalensis lectin (ESL) was analyzed. The phylogenetic relationship of the gene encoding lectin with other legume lectins was also established to investigate their evolutionary relationship via comparative genomics. Antimicrobial activity of ESL against selected pathogenic bacteria and fungi isolates was evaluated by the agar well diffusion method, using fluconazole (1 mg/ml) and streptomycin (1 mg/ml) as positive controls for fungi and bacteria sensitivity, respectively. Potent antimicrobial activity of ESL against Erwinia carotovora, Pseudomonas aeruginosa, Klebsiella pneumonia, Staphylococcus aureus, Aspergillus niger, Penicillium camemberti, and Scopulariopsis brevicaulis was observed, with inhibition zones ranging from 18 to 24 mm. Minimum inhibitory concentrations of ESL ranged between 50 and 400 μg/ml. Primer-directed polymerase chain reaction of E. senegalensis genomic DNA detected a 465-bp lectin gene with an open reading frame encoding a 134-amino acid polypeptide. The obtained nucleotide sequence of the ESL gene shared high sequence homology: 100, 100, and 98.18% with Erythrina crista-galli, Erythrina corallodendron, and Erythrina variegata lectin genes, respectively, suggesting that the divergence of Erythrina lectins might follow species evolution. This study concluded that ESL could be used to develop lectin-based antimicrobials, which could find applications in the agricultural and health sectors.