Classification of bacterial cell wall hydrolysases and their potentials as novel alternatives to antibiotics - a response to the letter of Biziulevicius and Kazlauskaite

Abstract

This is a response to the letter of Biziulevicius and Kazlauskaite, who made a few valuable comments on our recent paper published on the Journal of Applied Microbiology regarding the classification and potential clinic applications as alternative antibiotics of bacterial cell wall hydrolases (BCWH). We confirm that it is of significant practical and theoretical relevance to categorize BCWH according to their sources owing to their strikingly different antibacterial specificities, which are of critical importance to their potential clinic applications. Among the three groups of lytic enzymes, i.e. lysozymes, microlysins and virolysins, virolysins seem to be the most promising alternative antibiotics as a result of a few unique characteristics of this group of lytic enzymes.

Production and Application of Bacteriophage and Bacteriophage-Encoded Lysins

“…Lysozymes, which are defined here as lytic enzymes produced by animals or plants as a part of their defence against the invasion of bacteria, are the most well studied BCWHs. However, virolysins are deemed to be the most promising enzybiotics among the three groups of BCWHs because [52]: 1) they have the capacity of rapidly killing sensitive bacteria, even if these bacteria are resistant to lysozymes; 2) they have in general narrow spectra of sensitive bacteria, minimizing the disturbance to normal microflora; 3) there is a tremendous diversity of lytic bacteriophages in the biosphere [1], which guarantees the availability of virolysins targeting almost any Gram-positive bacteria; 4) the bacteriolytic activity of bacteriophages to their hosts is easily detectable, providing a solid basis for rational selection of bacteriophages for isolation of desired virolysins targeting specific pathogenic bacteria.…”

“…On a broader scope, virolysins belong to a group of bacterial cell wall hydrolases (BCWH), which can be classified into three sub-groups according to the sources of these enzymes: 1) lysozymes, BCWHs produced by animals and plants as an essential component of their innate defense system; 2) microlysins, BCWHs produced by microbes except those encoded by bacteriophages, i.e., virolysins; and 3) virolysins [52]. Lysozymes, which are defined here as lytic enzymes produced by animals or plants as a part of their defence against the invasion of bacteria, are the most well studied BCWHs.…”