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.

Helical Shape of Helicobacter pylori Requires an Atypical Glutamine as a Zinc Ligand in the Carboxypeptidase Csd4

“…Deletion of H. pylori csd4 led to the loss of helical shape, resulting in slightly curved or straight rods that were impaired in murine stomach colonization assays (8). A similar study in C. jejuni, a closely related human diarrheal pathogen, revealed that deletion of the csd4 homolog, pgp1, led to a similar straight rod phenotype with impaired chick colonization ability, a model representing the natural reservoir of this pathogen (9). HPLC analysis of H. pylori ⌬csd4 PG sacculi or purified disaccharide-linked tripeptide digested with Csd4 demonstrated production of a disaccharide dipeptide (i.e.…”

“…9 and 10). Homologs were identified primarily within the ␦ and ⑀ Proteobacteria, Deferribacteres, and Aquificae (9). Although primarily found in helical or curved rodshaped organisms, homologs of Csd4 were identified in a number of rod-shaped bacteria, including ones isolated from deep sea hydrothermal vents and coastal sediments.…”

Colonize, evade, flourish

“…For example, Campylobacter jejuni expresses Pgp1, a homolog of Csd4 in H. pylori. 57 Like csd4, deletion of pgp1 results in a straight, rod-shaped cell with defects in motility and colonization of the gastric epithelium. Enzymatically, Pgp1 possesses activity identical to that of Csd4, trimming PG tripeptides to dipeptides (Fig.…”

“…5C). 57 Clearly, remodeling of the PG layer on both large and small scales majorly impacts cell shape and allows the helical bacteria to adopt their characteristic shape.…”

Influência da vida séssil e planctônica no perfil de resistência antimicrobiana de Campylobacter jejuni isoladas de carcaças de frangos comercializadas no Brasil

“…Os determinantes genéticos da formação de biofilmes diferem entre as espécies, e pouco se sabe como as estirpes de uma mesma espécie conseguem características genéticas próprias na presença de diferentes origens genéticas (FRIRDICH et al, 2012;SULAEMAN et al, 2012).…”