Activity of a Holin-Endolysin System in the Insecticidal Pathogenicity Island of Yersinia enterocolitica

Abstract

is a pathogen that causes gastroenteritis in humans. Because of its low-temperature-dependent insecticidal activity, it can oscillate between invertebrates and mammals as host organisms. The insecticidal activity of strain W22703 is associated with a pathogenicity island of 19 kb (Tc-PAI ), which carries regulators and genes encoding the toxin complex (Tc). The island also harbors four phage-related and highly conserved genes of unknown functions, which are polycistronically transcribed. Two open reading frames showed significant homologies to holins and endolysins and exhibited lytic activity in cells upon overexpression. When a set of strains was tested in an equivalent manner, highly diverse susceptibilities to lysis were observed, and some strains were resistant to lysis. If cell lysis occurred (as demonstrated by membrane staining), it was more pronounced when two accessory elements of the cassette coding for an i-spanin and an o-spanin were included in the overexpression construct. The pore-forming function of the putative holin, HolY, was demonstrated by complementation of the lysis defect of a phage λ S holin mutant. In experiments performed with membrane preparations, ElyY exhibited high specificity for W22703 peptidoglycan, with a cleavage activity resembling that of lysozyme. Although the functionality of the lysis cassette from Tc-PAI was demonstrated in this study, its biological role remains to be elucidated. The knowledge of how pathogens survive in the environment is pivotal for our understanding of bacterial virulence. The insecticidal and nematocidal activity of spp., by which the bacteria gain access to nutrients and thus improve their environmental fitness, is conferred by the toxin complex (Tc) encoded on a highly conserved pathogenicity island termed Tc-PAI While the regulators and the toxin subunits of the island had been characterized in some detail, the role of phage-related genes within the island remained to be elucidated. Here, we demonstrate that this cassette encodes a holin, an endolysin, and two spanins that, at least upon overexpression, lyse strains.

A holin/peptidoglycan hydrolase‐dependent protein secretion system

“…Deliberate overproduction of the Y. enterocolitica W22703 holin and endopeptidase in E. coli was shown to result in cell lysis (Springer et al, 2018), which has also been observed when ChiW/ChiX are highly overproduced (Owen, 2016). However, in the native context S. marcescens DB10 chiW and chiX expression is carefully regulated (Hamilton et al, 2014), presumably to prevent the uncontrolled accumulation of these proteins to levels could induce lysis, and this also appears the case for the Y. enterocolitica system (Springer et al, 2018). This underscores the importance of studying the function of these proteins produced at native levels under physiological conditions wherever possible.…”

“…It has been shown that these two regulators control toxin induction in Yersinia enterocolytica strain W22703 at low temperatures (Starke et al, 2013). More recently, it was reported that the holin/endopeptidase/ spanin genes in the cluster are transcriptionally coupled, and that expression of these genes is exceptionally low (Springer et al, 2018).…”

“…It has been shown that these two regulators control toxin induction in Yersinia enterocolytica strain W22703 at low temperatures (Starke et al ., 2013). More recently, it was reported that the holin/endopeptidase/spanin genes in the cluster are transcriptionally coupled, and that expression of these genes is exceptionally low (Springer et al ., 2018). Deliberate overproduction of the Y. enterocolitica W22703 holin and endopeptidase in E. coli was shown to result in cell lysis (Springer et al ., 2018), which has also been observed when ChiW/ChiX are highly overproduced (Owen, 2016).…”

“…More recently, it was reported that the holin/endopeptidase/spanin genes in the cluster are transcriptionally coupled, and that expression of these genes is exceptionally low (Springer et al ., 2018). Deliberate overproduction of the Y. enterocolitica W22703 holin and endopeptidase in E. coli was shown to result in cell lysis (Springer et al ., 2018), which has also been observed when ChiW/ChiX are highly overproduced (Owen, 2016). However, in the native context S. marcescens DB10 chiW and chiX expression is carefully regulated (Hamilton et al ., 2014), presumably to prevent the uncontrolled accumulation of these proteins to levels could induce lysis, and this also appears the case for the Y. enterocolitica system (Springer et al ., 2018).…”

Dissecting the invasion of Galleria mellonella by Yersinia enterocolitica reveals metabolic adaptations and a role of a phage lysis cassette in insect killing

“…ElyY revealed an endopeptidase with high substrate specificity that cleaves yersinial murein. We also demonstrated that upon overexpression, the dual lysis cassette is able to lyse cells of E. coli and of several, but not all, Yersinia species including Y. enterocolitica and Y. pseudotuberculosis (15). Remarkably, HolY and ElyY lyse Y. enterocolitica at body temperature, but not at 15°C.…”