Cloning and characterization of the lysis protein LysSGF3 from Shigella Microviridae phage SGF3 for control of pathogenic bacteria and biofilms

Endolysins (lysins) are novel bactericidal agents derived from phages. In contrast, single-stranded DNA (ssDNA) phages can lyse host bacteria via an isolated lysis protein, with improved efficiency and speed compared to the binary lysis system “lysin-holin” employed by double-stranded DNA (dsDNA) phages. In this study, three uncharacterized proteins from Shigella Microviridae phage SGF3 were cloned and expressed. From them, a novel lysis protein, LysSGF3, was identified, and factors influencing its bactericidal activity and properties were investigated. These features were applied to biofilm control. LysSGF3 at a concentration of 100 μg/mL exhibited robust lysis activity of 76.13 % against S. flexneri 1.10599 at 37 °C and pH = 7. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of LysSGF3 on S. flexneri 1.10599 were 50 μg/mL and 300 μg/mL, respectively. Moreover, LysSGF3 exhibited a wider lysis spectrum than phage SGF3, with robust effects against 11 Gram-negative strains of Shigella, Escherichia coli, and Edwardsiella and three Gram-positive strains including Staphylococcus aureus and Bacillus. The biofilm formed by strains of Shigella, E. coli, and S. aureus experienced a removal rate of at least 50 %. At the same time, the combined biofilm of S. flexneri 1.10599 and other strains also experienced adequate removal. In summary, LysSGF3 is a promising new bactericidal agent that will provide alternative solutions to overcome antibiotic resistance.