ABSTRACTAs a potential antimicrobial, the bacteriophage lysin PlyG has been reported to specifically recognizeBacillus anthracisvegetative cells only and to killB. anthracisvegetative cells and its germinating spores. However, how PlyG interacts withB. anthracisspores remains unclear. Herein, a 60-amino-acid domain in PlyG (residues 106 to 165), located mainly in the previously identified catalytic domain, was found able to specifically recognizeB. anthracisspores but not vegetative cells. The exosporium of the spores was found to be the most probable binding target of this domain. This is the first time that a lysin for spore-forming bacteria has been found to have separate domains to recognize spores and vegetative cells, which might help in understanding the coevolution of phages with spore-forming bacteria. Besides providing new biomarkers for developing better assays for identifyingB. anthracisspores, the newly found domain may be helpful in developing PlyG as a preventive antibiotic to reduce the threat of anthrax in suspected exposures toB. anthracisspores.

Developing chimeric lysins with a wide lytic spectrum would be important for treating some infections caused by multiple pathogenic bacteria. In the present work, a novel chimeric lysin (Ply187N-V12C) was constructed by fusing the catalytic domain (Ply187N) of the bacteriophage lysin Ply187 with the cell binding domain (146-314aa, V12C) of the lysin PlyV12. The results showed that the chimeric lysin Ply187N-V12C had not only lytic activity similar to Ply187N against staphylococcal strains but also extended its lytic activity to streptococci and enterococci, such as Streptococcus dysgalactiae, Streptococcus agalactiae, Streptococcus pyogenes, Enterococcus faecium and Enterococcus faecalis, which Ply187N could not lyse. Our work demonstrated that generating novel chimeric lysins with an extended lytic spectrum was feasible through fusing a catalytic domain with a cell-binding domain from lysins with lytic spectra across multiple genera.