Bacteriophage – Salmonella enteritidis
The holin-endolysin lysis system is an essential and well-studied factor in the phage life cycle, as endolysins are a promising alternative to antibiotics and have even been used against Gram-positive bacteria.
Unfortunately, few endolysins can lyse Gram-negative bacteria from the outside because the peptidoglycan layer is protected by an envelope.
However, recent studies on a novel Salmonella phage (vB_Sal-S-S10) suggest that it carries a classical holin-endolysin lysis system that includes an overlapping holin-lysin gene and a novel lysin gene. The two endolysins encoded by these genes could lyse S. enteritidis externally, suggesting that they have natural extracellular antibacterial properties.
This information could be used to develop engineered endolysins as a therapy for bacterial infections.
The authors Xinrui Wang, Lili Han, Jiaqing Rong, Huiying Ren, Wenhua Liu, and Can Zhang published their findings in the article ‘Endolysins of bacteriophage vB_Sal-S-S10 can naturally lyse Salmonella enteritidis‘, dated 21 November 2022.
Key topics include:
- A new Salmonella phage vB_Sal-S-S10 (S10) was characterized and found to infect 51.4% of S. enteritidis strains tested.
- Phage S10 has a classical holin-endolysin lysis system carrying an overlapping holin-lysin gene and a novel lysin gene.
- Both endolysins encoded by the lysine genes could externally lyse S. enteritidis, making them promising alternatives to antibiotics for the treatment of infections with multidrug-resistant Gram-negative bacteria.
The holin-endolysin lysis system plays an essential role in the phage life cycle. Endolysins are promising alternatives to antibiotics, and have been successfully used against Gram-positive bacteria. However, a few endolysins can externally lyse Gram-negative bacteria, due to the inaccessible peptidoglycan layer covered by the envelope.
This study investigated the lysis system of a new Siphoviridae bacteriophage vB_Sal-S-S10 (S10), which, that was isolated from broiler farms, was found to be able to infect 51.4% (37/72) of tested S. enteritidis strains. Phage S10 genome had a classic holin-endolysin lysis system, except that one holin and one endolysin gene were functionally annotated. The orf 22 adjacent to the lysis cassette was identified as a new endolysin gene. Antibacterial activity assays showed that holin had an intracellular penetrating activity against S. enteritidis 35; both endolysins acted on the cell envelope of S. enteritidis 35 and showed a natural extracellular antibacterial activity, leading to a ~ 1 log titer decrease in 30 min. Protein characterization of lysin1 and lysin2 revealed that the majority of the N-terminus and the C-terminus were hydrophobic amino acids or positively charged.
In this study, a new Salmonella phage vB_Sal-S-S10 (S10) was characterized and showed an ideal development prospect. Phage S10 has a classic holin-endolysin lysis system, carrying an overlapping holin-lysin gene and a novel lysin gene. Both endolysins coded by lysin genes could externally lyse S. enteritidis. The natural extracellular antibacterial character of endolysins would provide necessary information for the development of engineering endolysin as the antibiotic alternative against the infection with multidrug-resistant gram-negative bacteria.
Keywords: Antibacterial activity; Bacteriophage vB_Sal-S-S10; Biological and genomic character; Endolysin; Holin; Salmonella enteritidis.
Copyright: the authors