title: Peptidoglycan LD-carboxypeptidase Pgp2 influences Campylobacter jejuni helical cell shape and pathogenic properties and provides the substrate for the DL-carboxypeptidase Pgp1.
abstract: Despite the importance of Campylobacter jejuni as a pathogen, little is known about the fundamental aspects of its peptidoglycan (PG) structure and factors modulating its helical morphology. A PG dl-carboxypeptidase Pgp1 essential for maintenance of C. jejuni helical shape was recently identified. Bioinformatic analysis revealed the CJJ81176_0915 gene product as co-occurring with Pgp1 in several organisms. Deletion of cjj81176_0915 (renamed pgp2) resulted in straight morphology, representing the second C. jejuni gene affecting cell shape. The PG structure of a Δpgp2 mutant showed an increase in tetrapeptide-containing muropeptides and a complete absence of tripeptides, consistent with ld-carboxypeptidase activity, which was confirmed biochemically. PG analysis of a Δpgp1Δpgp2 double mutant demonstrated that Pgp2 activity is required to generate the tripeptide substrate for Pgp1. Loss of pgp2 affected several pathogenic properties; the deletion strain was defective for motility in semisolid agar, biofilm formation, and fluorescence on calcofluor white. Δpgp2 PG also caused decreased stimulation of the human nucleotide-binding oligomerization domain 1 (Nod1) proinflammatory mediator in comparison with wild type, as expected from the reduction in muropeptide tripeptides (the primary Nod1 agonist) in the mutant; however, these changes did not alter the ability of the Δpgp2 mutant strain to survive within human epithelial cells or to elicit secretion of IL-8 from epithelial cells after infection. The pgp2 mutant also showed significantly reduced fitness in a chick colonization model. Collectively, these analyses enhance our understanding of C. jejuni PG maturation and help to clarify how PG structure and cell shape impact pathogenic attributes.
authors.affiliation: From the Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Emilisa
authors.initials: E
authors.lastname: Frirdich
authors.forename: Jenny
authors.initials: J
authors.lastname: Vermeulen
authors.forename: Jacob
authors.initials: J
authors.lastname: Biboy
authors.forename: Fraser
authors.initials: F
authors.lastname: Soares
authors.forename: Michael E
authors.initials: ME
authors.lastname: Taveirne
authors.forename: Jeremiah G
authors.initials: JG
authors.lastname: Johnson
authors.forename: Victor J
authors.initials: VJ
authors.lastname: DiRita
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Girardin
authors.forename: Waldemar
authors.initials: W
authors.lastname: Vollmer
authors.forename: Erin C
authors.initials: EC
authors.lastname: Gaynor
mesh_terms: D018441:Biofilms / Q000254:growth & development; D002169:Campylobacter Infections / Q000382:microbiology*; D016123:Campylobacter jejuni / Q000166:cytology* / Q000201:enzymology* / Q000472:pathogenicity / Q000502:physiology; D002268:Carboxypeptidases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004847:Epithelial Cells / Q000382:microbiology*; D017353:Gene Deletion; D054884:Host-Pathogen Interactions; D006801:Humans; D010457:Peptidoglycan / Q000737:chemistry / Q000378:metabolism
chemical_list: D010457:Peptidoglycan; D002268:Carboxypeptidases; C021505:LD-carboxypeptidase
keywords: Bacterial Cell Shape; Campylobacter; Carboxypeptidase; Host-Pathogen Interactions; Microbial Pathogenesis; Peptidoglycan