| Abstract [eng] |
Bacteriocins are a diverse group of ribosomally synthesized antimicrobial peptides produced by bacteria to inhibit the growth of competing microorganisms. These compounds have gained attention as promising alternatives to traditional chemical products due to their high specificity, low toxicity, and potential applications in agriculture, food preservation, and medicine. Among the various bacteriocins, lasso peptides and LCI-type bacteriocins represent structurally unique subgroups. Lasso peptides are characterized by a threaded lasso topology that provides resistance to heat and proteolysis, while LCI-type peptides are small, heat-stable antimicrobials. Despite their potential, the native production of these bacteriocins is often limited by low yields and the difficulty of cultivating producer strains under laboratory conditions. The aim of this research was to heterologously synthesize and characterize novel bacteriocins with antimicrobial activity against phytopathogenic bacteria. To achieve this, objectives were pursued: the heterologous expression of lasso peptide and LCI-type bacteriocins in Escherichia coli and Lactococcus lactis host strains; verification of bacteriocin production through Tricine-SDS-PAGE analysis; purification of the expressed LCI peptides using Ni²⁺-affinity and ion-exchange chromatography; and evaluation of the antibacterial activity of the synthesized peptides against selected phytopathogenic bacterial strains. The results showed successful heterologous expression of LCI-type bacteriocins LCI1, LCI2, and LCI3 in E. coli BL21 (DE3), as confirmed by Tricine-SDS-PAGE. LCI1 and LCI2 peptides were subsequently purified using Ni²⁺-affinity and ion-exchange chromatography, while the purification of LCI3 was not performed. In contrast, heterologous expression of the lasso peptide in both E. coli and L. lactis cells was unsuccessful. Antimicrobial activity assays revealed no inhibitory effect of either the lasso peptide cell lysates or the purified LCI peptides against selected phytopathogenic bacteria, which may be attributed to insufficient LCI peptide concentrations or incomplete post-translational modifications of the lasso peptide in the heterologous host. |
