The endolysin from the Enterococcus faecalis bacteriophage VD13 and conditions stimulating its lytic activity.

Bacteriophages produce endolysins (peptidoglycan hydrolases) to lyse the host cell from within and release nascent bacteriophage particles. Recombinant endolysins can lyse Gram-positive bacteria when added exogenously. As a potential alternative antimicrobial, we cloned and expressed the enterococcal VD13 bacteriophage endolysin. VD13 endolysin has a CHAP catalytic domain with 92% identity with the bacteriophage IME-EF1 endolysin. The predicted size of VD13 endolysin is ∼27 kDa as verified by SDS-PAGE. The VD13 endolysin lyses Enterococcus faecalis strains, but not E. faecium or other non-enterococci. VD13 endolysin has activity from pH 4 to pH 8, with peak activity at pH 5, and exhibits greater activity in the presence of calcium. Optimum activity at pH 5 occurs in the absence of NaCl. VD13 endolysin, in ammonium acetate (C2H3O2NH4) calcium chloride (CaCl2) buffer pH 5, is stimulated to higher activity upon heating at temperatures up to 65°C for 30 min, whereas activity is lost upon heating to 42°C, in pH 7 buffer. Published by Oxford University Press on behalf of FEMS 2016. This work is written by (a) US Government employee(s) and is in the public domain in the US.