Antibacterial activity of a prophage lysin Sply828 from fish-derived Streptococcus parauberis

Abstract:

[Background] Streptococcus parauberis is a major aquatic pathogen which has gradually evolved new serotypes and multi-drug resistance. Therefore, it is urgent to develop a new antibacterial drug for the prevention and treatment of the disease caused by this pathogen. Studies have demonstrated that a lysin encoded by a prophage can effectively kill the host and has a good prospect of antibacterial application. [Objective] In this paper, we investigated the host spectrum of the prophage lysin from S. parauberis and optimized the conditions for the lytic activity. [Methods] We used bioinformatics tools to analyze the whole genomic sequence of the S. parauberis strain KRS02083 and discovered a lysin gene Sply828. By gene cloning, protein expression and purification, we obtained the lysin Sply828. We then evaluated the activities against different bacteria and the optimal lysis conditions of Sply828 by performing the turbidity decrease assay. [Results] Sply828 displayed the best activity against fish-derived S. parauberis and exhibited the highest activity against the bacteria in the exponential growth phase. This enzyme had the highest activity at 28 °C and pH 6.2, and its activity can be improved by Ca²⁺ and Mg²⁺ while inhibited by Zn²⁺, Cu²⁺, Fe²⁺, and Ni²⁺. [Conclusion] The prophage lysin Sply828 existing in the genomic sequence of S. parauberis possesses efficient and specific bactericidal activity, providing a preliminary basis for the prevention and control of the disease caused by S. parauberis.