Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 25, 2006
Publication Date: October 19, 2006
Citation: Donovan, D.M., Foster Frey, J.A. 2006. Bacteriophage phi11 endolysin has antimicrobial activity against the mastitis pathogens staphylococcus aureus and coagulase negative staphylococcus. Applied and Environmental Microbiology. 265(1):133-139. Interpretive Summary: Mastitis is an infection of dairy cattle mammary glands. It costs the US dairy industry $2 billion dollars annually. In an effort to identify novel antimicrobial proteins for use against mastitis causing pathogens, bacteriophage endolysins are being examined. Staphylococcus aureus is one of the most serious mastitis pathogens. The bacteriophage phi11 has an enzyme (endolysin) that can degrade the cell wall of S. aureus and thus kill the cell. When examined, the phi11 endolysin is functional at the ph and calcium concentration of milk and when the protein is truncated, we can identify the essential protein sequences required for this lytic activity.
Technical Abstract: The Staphylococcus aureus bacteriophage phi11 endolysin has two peptidoglycan activity domains, CHAP endopeptidase and amidase. In turbidity reduction assays on un-treated cells, the purified protein can lyse staphylococcal mastitis pathogens including S. aureus and multiple coagulase negative staphylococci (S. chronogenes, S. epidermis, S. hyicus, S. simulans, S. warneri and, S. xylocus), making it a strong candidate antimicrobial. The endolysin was tested and shown to maintain this lytic activity over a broad pH range, including that of milk, pH 6.7, and has a peak of activity at the free calcium concentration of milk (3mM). The lytic activity of the phi11 endolysin in turbidity assays is comparable to that of the well characterized lysostaphin. A truncated phi11 protein with just 194 amino acids (contains the entire CHAP domain) shows no lysis of Streptococcus agalactiae but is lytic against untreated S. aureus despite the lack of the SH3b cell wall binding domain.