The Campylobacter jejuni Dps Homologue Is Important forIn VitroBiofilm Formation and Cecal Colonization of Poultry and May Serve as a Protective Antigen for Vaccination

Abstract

<jats:title>ABSTRACT</jats:title><jats:p>In this work, we investigated the<jats:named-content content-type="genus-species">Campylobacter jejuni dps</jats:named-content>(DNA binding protein from starved cells) gene for a role in biofilm formation and cecal colonization in poultry.<jats:italic>In vitro</jats:italic>biofilm formation assays were conducted with stationary-phase cells in cell culture plates under microaerophilic conditions. These studies demonstrated a significant (&gt;50%) reduction in biofilm formation by the<jats:named-content content-type="genus-species">C. jejuni dps</jats:named-content>mutant compared to that by the wild-type strain. Studies in poultry also demonstrated the importance of the<jats:italic>dps</jats:italic>gene in host colonization by<jats:named-content content-type="genus-species">C. jejuni</jats:named-content>. Real-time PCR analysis of mRNA extracted from the cecal contents of poultry infected with wild-type<jats:named-content content-type="genus-species">C. jejuni</jats:named-content>indicated that the<jats:italic>dps</jats:italic>gene is upregulated 20-fold during poultry colonization. Cecal colonization was greater than 5 log CFU lower in chicks infected with the<jats:italic>dps</jats:italic>mutant than chicks infected with the wild-type<jats:named-content content-type="genus-species">C. jejuni</jats:named-content>strain. Moreover, the<jats:italic>dps</jats:italic>mutant failed to colonize 75% of the chicks following challenge with 10<jats:sup>5</jats:sup>CFU. Preliminary studies were conducted in chicks by parenteral vaccination with a recombinant Dps protein or through oral vaccination with a recombinant attenuated<jats:italic>Salmonella enterica</jats:italic>strain synthesizing the<jats:named-content content-type="genus-species">C. jejuni</jats:named-content>Dps protein. No reduction in<jats:named-content content-type="genus-species">C. jejuni</jats:named-content>was noted in chicks vaccinated with the parenteral recombinant protein, whereas, a 2.5-log-unit reduction of<jats:named-content content-type="genus-species">C. jejuni</jats:named-content>was achieved in chicks vaccinated with the attenuated<jats:italic>Salmonella</jats:italic>vector after homologous challenge. Taken together, this work demonstrated the importance of Dps for biofilm formation and poultry colonization, and the study also provides a basis for continued work using the Dps protein as a vaccine antigen when delivered through a<jats:italic>Salmonella</jats:italic>vaccine vector.</jats:p>

Campylobacter jejuni Dps Protein Binds DNA in the Presence of Iron or Hydrogen Peroxide

“…Our data suggest that Dps could act to protect DNA under low pH; this hypothesis is supported by the fact that C. jejuni Dps expression is induced under acid stress (48) and during host colonization (35). Furthermore, it was shown that E. coli Dps contributes to acid tolerance by protecting DNA under low pH (20), and a dps gene isolated from a metagenome library conferred acid resistance to E. coli (49).…”

“…The concerted activation of C. jejuni Dps DNA binding in response to low pH, H 2 O 2 , and Fe 2ϩ would effectively protect DNA during host colonization and explain, at least in part, the described inability of C. jejuni dps mutants to colonize poultry and piglets (34,35). Other animal pathogens, such as Haemophilus influenzae and Salmonella enterica, also rely on Dps for bacterial resistance during host colonization (21,50).…”

“…In C. jejuni, the gene encoding the Dps protein is required for resistance to H 2 O 2 stress (17), biofilm formation, and colonization of poultry and piglets (34,35). Previous studies failed to detect C. jejuni Dps-DNA binding activity (17 …”

Peptidoglycan Acetylation of Campylobacter jejuni Is Essential for Maintaining Cell Wall Integrity and Colonization in Chicken Intestines

“…PG plays an important role in maintaining cell shape, and structural changes in PG affect various phenotypes, such as motility and biofilm formation (8,9). Reduced motility and/or biofilm formation have been reported to reduce C. jejuni colonization in chicken intestines (10,11).…”

“…PG plays an important role in maintaining cell shape, and structural changes in PG affect various phenotypes, such as motility and biofilm formation (8, 9). Reduced motility and/or biofilm formation have been reported to reduce C. jejuni colonization in chicken intestines (10,11).O-Acetylation, N-deacetylation, and N-glycosylation are common secondary modifications of glycan strands of PG and confer resistance against degrading enzymes such as lysozyme (12). The reported base-labile acetate contents of PG glycan strands purified from two C. jejuni strains were 55.7% and 62.…”