Design, expression and characterization of lactiscin—A novel broad-spectrum peptidic bacteriocin

Bacteria-derived antimicrobial peptides known as peptidic bacteriocins offer a promising alternative to traditional antibiotics in the face of the emergence of multidrug-resistant bacteria. Here, a nucleotide sequence of the gene encoding Lactococcus lactis-derived peptidic bacteriocin designated as lactiscin selectively identified from the GenBank® database was synthesized with an added 6⋅His sequence and cloned into Escherichia coli. Upon low-temperature expression at 16 °C, the His-tagged peptide could be produced in both soluble form and insoluble inclusions. Efficient purification of the soluble His-tagged peptide was achieved via immobilized-Ni2+ affinity chromatography (IMAC) and its estimated molecular mass of ∼13.4 kDa was determined by tricine-sodium dodecyl sulfate polyacrylamide gel electrophoresis. The purified peptide was highly active against both Gram-positive and Gram-negative bacteria as it exhibited a minimal inhibitory concentration of 0.45 mg/mL, 0.15 mg/mL, 0.35 mg/mL and 0.45 mg/mL against. Escherichia coli, Vibrio parachemolyticus, Staphylococcus aureus and Micrococcus luteus, respectively. In addition, the lactiscin peptide still retained antimicrobial activity over a pH range of 3.0–12.0 and heat stability of 100 °C for 30 min. A membrane integrity study revealed that this peptidic bacteriocin was able to induce E. coli membrane permeabilization in a concentration-dependent manner, albeit it showed a negligible toxic effect on erythrocytic cells. Gel retardation assay demonstrated that the lactiscin bacteriocin could suppress the migration of genomic DNA extracted from pathogenic bacteria, suggesting the presence of bacteriocin-responsive binding genomic. Our findings of lactiscin—a novel broad-spectrum bacteriocin would be a valuable additive for the application of food industry as a potential bio-preservative.