Correction: Peptidoglycan-Modifying Enzyme Pgp1 Is Required for Helical Cell Shape and Pathogenicity Traits in Campylobacter jejuni

Abstract

The impact of bacterial morphology on virulence and transmission attributes of pathogens is poorly understood. The prevalent enteric pathogen Campylobacter jejuni displays a helical shape postulated as important for colonization and host interactions. However, this had not previously been demonstrated experimentally. C. jejuni is thus a good organism for exploring the role of factors modulating helical morphology on pathogenesis. We identified an uncharacterized gene, designated pgp1 (peptidoglycan peptidase 1), in a calcofluor white-based screen to explore cell envelope properties important for C. jejuni virulence and stress survival. Bioinformatics showed that Pgp1 is conserved primarily in curved and helical bacteria. Deletion of pgp1 resulted in a striking, rod-shaped morphology, making pgp1 the first C. jejuni gene shown to be involved in maintenance of C. jejuni cell shape. Pgp1 contributes to key pathogenic and cell envelope phenotypes. In comparison to wild type, the rod-shaped pgp1 mutant was deficient in chick colonization by over three orders of magnitude and elicited enhanced secretion of the chemokine IL-8 in epithelial cell infections. Both the pgp1 mutant and a pgp1 overexpressing strain -which similarly produced straight or kinked cells -exhibited biofilm and motility defects. Detailed peptidoglycan analyses via HPLC and mass spectrometry, as well as Pgp1 enzyme assays, confirmed Pgp1 as a novel peptidoglycan DL-carboxypeptidase cleaving monomeric tripeptides to dipeptides. Peptidoglycan from the pgp1 mutant activated the host cell receptor Nod1 to a greater extent than did that of wild type. This work provides the first link between a C. jejuni gene and morphology, peptidoglycan biosynthesis, and key host-and transmission-related characteristics.

Virulence Traits of Inpatient Campylobacter jejuni Isolates, and a Transcriptomic Approach to Identify Potential Genes Maintaining Intracellular Survival

“…Recent studies reported that during oxidative stress conditions, C. jejuni transformed its spiral shape to a coccoid one [81]. Although we did not evaluate the morphological state of the internalized C. jejuni, decreased expression of pgp1 and pgp2 [13,111], two genes contributing to the helical cell shape, suggested that the bacterium lost its curved shape in the vacuole. In the rod shape formation, there is increased expression of penicillin-binding protein genes (pbp) [71,112], supporting our findings as elevated expression levels of pbpA, pbpB, and pbpC in the internalized C. jejuni following 3 h of internalisation were detected ( Supplementary Table S2C).…”

Structural basis for the recognition of muramyltripeptide byHelicobacter pyloriCsd4, aD,L-carboxypeptidase controlling the helical cell shape

“…The substrate of Csd4, mDAP-containing muramyltripeptide, is an agonist for the cytosolic innate immune receptor Nod1 (Girardin et al, 2003;Chamaillard et al, 2003), and thus a decreased amount of muramyltripeptide as a result of catalysis by Csd4 is likely to affect Nod1 activation and ultimately NF-B activity. Ápgp1, the mutant of the Csd4 homologue in C. jejuni, produces a significantly higher interleukin-8 (IL-8) response in human epithelial cells (INT407) than does wild-type C. jejuni (Frirdich et al, 2012;Sycuro et al, 2012), even though the Ácsd4 mutant is comparable to wildtype H. pylori in pro-inflammatory cytokine induction of gastric epithelial AGS cells (Sycuro et al, 2012). Therefore, it is suggested that d,l-carboxypeptidation by Csd4 homologues could affect the overall amount of released mDAP-containing muramyltripeptides, affect the helical shape and influence immune detection (Frirdich et al, 2012;Wyckoff et al, 2012).…”

“…3), but is absent in other CPases with known structures. Interestingly, Csd4 homologues are mainly found in spiral-shaped bacteria (Sycuro et al, 2012;Frirdich et al, 2012). Next, the CPase domain (Met22-Asn267) of H. pylori Csd4 shows relatively large r.m.s.…”

“…In many bacteria, the peptidoglycan layer is remodelled by a number of cell-wall hydrolases as well as synthetases for peptidoglycan maturation, regulation of cell-wall growth, cell division, peptidoglycan turnover and recycling, cell lysis and the release of peptidoglycan fragments for host-pathogen interactions (Vollmer, Joris et al, 2008). In H. pylori, seven cell shape-determining genes have been identified to date: csd1, csd2, csd3/hdpA, ccmA, csd4, csd5 and csd6 (Sycuro et al, 2010(Sycuro et al, , 2012(Sycuro et al, , 2013Bonis et al, 2010;Frirdich et al, 2012). Peptidoglycan cross-linking relaxation by these proteins is critical for the helical cell shape of H. pylori and for stomach colonization.…”

“…The Ácsd4 mutant with the straight rod cell shape shows impaired stomach colonization (Sycuro et al, 2012). A Csd4 homologue in Campylobacter jejuni, Pgp1, exhibits a similar Zn 2+ -dependent d,l-CPase activity against the monomeric disaccharide tripeptide substrate and promotes the helical rod shape of this organism (Frirdich et al, 2012). It has 41% sequence identity and 60% similarity to H. pylori Csd4.…”