Phage endolysin Lysin1902: prokaryotic expression and evaluation of its bactericidal activity combined with ε-poly-lysine

Abstract:

[Objective] To investigate the antibacterial effect of the phage endolysin Lysin1902 combined with ε-poly-lysine (ε-PL) on Escherichia coli O157:H7. [Methods] We employed Mega to construct the phylogenetic tree and used online tools to analyze the amino acid sequence of Lysin1902. After prokaryotic expression, Lysin1902 was purified. We then detected the lytic activity of Lysin1902 against autoclaved E. coli O157:H7 by plate lysis assay and detected the lysis activity of Lysin1902 or ε-PL on live E. coli O157:H7 in 96-well plates. Further, we adopted checkerboard assay to measure the bactericidal activity of Lysin1902 combined with ε-PL. [Results] We successfully expressed and purified Lysin1902. Lysin1902 showed lytic activity against autoclaved E. coli O157:H7 but cannot effectively lyse live E. coli strains. After the addition of Lysin1902, the concentration of ε-PL that could completely control the proliferation of E. coli O157:H7 decreased from 0.7 mg/mL to 0.1 mg/mL. [Conclusion] Lysin1902 was successfully expressed and purified. Lysin1902 alone has no lytic activity against E. coli O157:H7, while the combined use of Lysin1902 with ε-PL significantly increased the lytic activity of ε-PL against E. coli O157:H7.