Characterization of staphylococcal endolysin LysSAP33 possessing untypical domain composition

Abstract

Endolysin, a peptidoglycan hydrolase derived from bacteriophage, has been suggested as an alternative antimicrobial agent. Many endolysins on staphylococcal phages have been identified and applied extensively against Staphylococcus spp. Among them, LysK-like endolysin, a well-studied staphylococcal endolysin, accounts for most of the identified endolysins. However, relatively little interest has been paid to LysKunlike endolysin and a few of them has been characterized. An endolysin LysSAP33 encoded on bacteriophage SAP33 shared low homology with LysK-like endolysin in sequence by 41% and domain composition (CHAP-unknown CBD). A green fluorescence assay using a fusion protein for LysSAP33_CBD indicated that the CBD domain (157-251 aa) was bound to the peptidoglycan of S. aureus. The deletion of LysSAP33_CBD at the C-terminal region resulted in a significant decrease in lytic activity and efficacy. Compared to LysK-like endolysin, LysSAP33 retained its lytic activity in a broader range of temperature, pH, and NaCl concentrations. In addition, it showed a higher activity against biofilms than LysK-like endolysin. This study could be a helpful tool to develop our understanding of staphylococcal endolysins not belonging to LysK-like endolysins and a potential biocontrol agent against biofilms.