Characterization and structure analysis of a novel bacteriocin, lacticin Z, produced by Lactococcus lactis QU 14.

The research focuses on the discovery and analysis of a new bacterial toxin, lacticin Z, produced by a strain of bacteria found in a horse’s intestinal tract. This toxin effectively kills various strains of gram-positive bacteria and maintains stability even under high heat and alkaline conditions.

Isolation and Purification of Lacticin Z

• The bacterium Lactococcus lactis QU 14, which produces lacticin Z, was isolated from a horse’s intestines.
• To extract and purify lacticin Z, a multi-step process involving hydrophobic-interaction, cation-exchange chromatography, and reverse-phase HPLC was used.

Molecular Characteristics of Lacticin Z

• Using ESI-TOF MS, the team was able to determine the molecular mass of lacticin Z to be 5,968.9 Da.
• Lacticin Z was found to be made up of 53 amino acid residues and does not have any leader sequence or signal peptide often found in other proteins.
• Homology, or similar characteristics, was found between lacticin Z and other bacteriocins such as lacticin Q, aureocin A53, and mutacin BHT-B. This implies that lacticin Z might act in a similar fashion or have similar structures to these other bacteriocins.

Antibacterial Activity and Stability of Lacticin Z

• Lacticin Z was found to be effective against various Gram-positive bacteria, as indicated by its nanomolar range of Minimum Inhibitory Concentrations (MICs).
• The bacteriocin was found to be extremely hardy, maintaining complete stability up to a temperature of 100 degrees Centigrade.
• Unlike many bacteriocins from Lactic Acid Bacteria (LAB), lacticin Z remained stable under alkaline conditions rather than acidic ones.

Conclusion

• Based on its unique characteristics, researchers concluded that lacticin Z represents a new type of bacteriocin. This opens up opportunities for its potential use in various applications, particularly those that require conditions of high heat or alkalinity.