Recent Advances in Endolysin Engineering.

Antimicrobial resistance threatens a new "dark age" in medical practice. Chronic antibiotic overuse has driven the rise in antimicrobial resistance and promoted the emergence of multidrug-resistant organisms. To address this problem, researchers have developed new approaches. Antimicrobials derived from bacteriophage, which are viruses that target bacteria, are promising candidates. Amongst these candidates, bacteriophage enzymes used in the viral replication cycle are of significant interest. Specifically, endolysins are used by bacteriophage to lyse the bacterial cell wall, leading to structural collapse and cell lysis. Researchers are increasingly applying these proteins externally to multidrug-resistant organisms as a novel antimicrobial treatment. Following this increased interest, many studies have presented protein engineering methods to further enhance the effectiveness of endolysins as antimicrobials. These methods include attachment of membrane-permeabilizing peptides, domain-swapping, and catalytic-site modification. Recent advances in all three fields have seen the implementation of tools like novel in silico design pipelines and library-based screening methods. This review summarizes these recent advances in the rapidly developing field of endolysin engineering and discusses potential future directions in this field.