Peptidoglycan ld-Carboxypeptidase Pgp2 Influences Campylobacter jejuni Helical Cell Shape and Pathogenic Properties and Provides the Substrate for the dl-Carboxypeptidase Pgp1

• Published in: The Journal of biological chemistry 2014-03, Vol.289 (12), p.8007-8018
• Main Authors: Frirdich, Emilisa, Vermeulen, Jenny, Biboy, Jacob, Soares, Fraser, Taveirne, Michael E., Johnson, Jeremiah G., DiRita, Victor J., Girardin, Stephen E., Vollmer, Waldemar, Gaynor, Erin C.
• Format: Article
• Language: English
• Subjects: Bacterial Cell Shape; Biofilms - growth & development; Campylobacter; Campylobacter Infections - microbiology; Campylobacter jejuni; Campylobacter jejuni - cytology; Campylobacter jejuni - enzymology; Campylobacter jejuni - pathogenicity; Campylobacter jejuni - physiology; Carboxypeptidase; Carboxypeptidases - genetics; Carboxypeptidases - metabolism; Cell Line; Epithelial Cells - microbiology; Gene Deletion; Host-Pathogen Interactions; Humans; Microbial Pathogenesis; Microbiology; Peptidoglycan; Peptidoglycan - chemistry; Peptidoglycan - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.491829

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. Background:C. jejuni helical shape is important to pathogenesis. Results: Deletion of pgp2 results in loss of C. jejuni helical shape and change in peptidoglycan structure and pathogenic properties. Conclusion: Pgp2 is a ld-carboxypeptidase cleaving peptidoglycan tetrapeptides to tripeptides. Significance: Characterization of enzymes involved in C. jejuni peptidoglycan and cell shape maintenance is crucial to the understanding of fundamental properties of this organism.