The Holin-Endolysin Lysis System of the OP2-Like Phage X2 Infecting Xanthomonas oryzae pv. oryzae

Abstract

Most endolysins of dsDNA phages are exported by a holin-dependent mechanism, while in some cases endolysins are exported via a holin-independent mechanism. However, it is still unclear whether the same endolysins can be exported by both holin-dependent and holin-independent mechanisms. This study investigated the lysis system of OP2-like phage X2 infecting Xanthomonas oryzae pv. oryzae, causing devastating bacterial leaf blight disease in rice. Based on bioinformatics and protein biochemistry methods, we show that phage X2 employs the classic "holin-endolysin" lysis system. The endolysin acts on the cell envelope and exhibits antibacterial effects in vitro, while the holin facilitates the release of the protein into the periplasm. We also characterized the role of the transmembrane domain (TMD) in the translocation of the endolysin across the inner membrane. We found that the TMD facilitated the translocation of the endolysin via the Sec secretion system. The holin increases the efficiency of protein release, leading to faster and more efficient lysis. Interestingly, in E. coli, the expression of either holin or endolysin with TMDs resulted in the formation of long rod shaped cells. We conclude that the TMD of X2-Lys plays a dual role: One is the transmembrane transport while the other is the inhibition of cell division, resulting in larger cells and thus in a higher number of released viruses per cell.

Functional Analysis of the Endopeptidase and Holin From Planktothrix agardhii Cyanophage PaV-LD

“…The co-existence of holin and endopeptidase had an obvious bactericidal effect on E. coli than that of holin or endopeptidase alone, which indicated that holin might help the release of endopeptidase. Similar phenomena have been reported in other phages, including the lytic systems of bacteriophage phiSASD1 and OP2-Like Phage X2 ( Nl et al, 2020 ; Wu et al, 2021 ).…”

Isolation of bacteriophages infecting Xanthomonas oryzae pv. oryzae and genomic characterization of novel phage vB_XooS_NR08 for biocontrol of bacterial leaf blight of rice

“…In most of the previously reported Xoophages, members of holins and endolysins have been found involved in the lysis function. Holins create holes or pores in the lipid bilayer membrane of the host bacterium, thus allowing other enzymes of the lysis module to pass through the holes, whereas Rz spanin like lysis protein assists the lysozyme to enter the outer membrane from the inner membrane while one among the endolysins is peptidoglycan endopeptidase escapes through the holes and cleaves the peptide moiety, the structural portion of the bacterial cell wall ( Wu et al, 2021 ). All these enzymatic activities lead to the difference in osmotic pressure between the bacterial cell and its surrounding environment, thus finally resulting in complete cell lysis and release of progeny phage particles.…”

Characterization and Genomic Analysis of Escherichia coli O157:H7 Phage UAE_MI-01 Isolated from Birds

“…This is also evident from the morphology of the plaques ( Figure 1 ) and one-step growth ( Figure 2 ). Most tailed phages make use of the archetypical holin-endolysis system to induce the lysis of the host cell and the release of virions [ 36 , 37 , 38 ]. Holin-like class I and class II genes and lysin were identified, thus indicating lytic activity.…”