title: Characterization of two putative cytochrome c peroxidases of Campylobacter jejuni involved in promoting commensal colonization of poultry.
abstract: Campylobacter jejuni is a leading cause of bacterial gastroenteritis in humans throughout the world, but infection of animals, especially poultry, results in a commensal colonization of the intestines. We previously found that a mutant lacking docA, which encodes a putative cytochrome c peroxidase (CCP), demonstrates up to a 10(5)-fold reduction in colonization of the chick cecum compared to wild-type C. jejuni strain 81-176. Predictions from genomic sequences identified CJJ0382 as a second locus in C. jejuni encoding a CCP, making the bacterium unusual in having two putative CCPs. To understand what advantages are imparted by having two putative CCPs, we compared the colonization requirements of C. jejuni mutants lacking DocA or Cjj0382. Unlike the DeltadocA mutant, a DeltaCJJ0382 mutant demonstrates a maximal 50-fold colonization defect that is dependent on the inoculum dose. The colonization differences of mutants lacking DocA or Cjj0382 suggest that the two predicted CCPs are unlikely to perform redundant functions during in vivo growth. In the characterizations of DocA and Cjj0382, we found that they are stable periplasmic proteins with an apparent heme-dependent peroxidase activity, which are characteristics of bacterial CCPs. However, the peroxidase activities of the proteins do not appear to contribute to resistance to hydrogen peroxide. Instead, we found that resistance to hydrogen peroxide in C. jejuni is mostly attributed to the cytoplasmic catalase KatA. Our data suggest that DocA and Cjj0382 have characteristics of CCPs but likely perform different physiological functions for the bacterium in colonization that are not related to resisting oxidative stress.
authors: University of Texas Southwestern Medical Center, Department of Microbiology, 5323 Harry Hines Boulevard, Dallas, TX 75390-9048, USA.
authors: Lacey K
authors: LK
authors: Bingham-Ramos
authors: David R
authors: DR
authors: Hendrixson
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D016123:Campylobacter jejuni / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D002432:Cecum / Q000382:microbiology; D002645:Chickens; D015169:Colony Count, Microbial; D003578:Cytochrome-c Peroxidase / Q000235:genetics / Q000502:physiology*; D005243:Feces / Q000382:microbiology; D041981:Gastrointestinal Tract / Q000382:microbiology*; D017353:Gene Deletion; D006418:Heme / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology; D050296:Microbial Viability; D019897:Periplasm / Q000737:chemistry; D033903:Periplasmic Proteins / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D033903:Periplasmic Proteins; D006418:Heme; D006861:Hydrogen Peroxide; D003578:Cytochrome-c Peroxidase; D002374:Catalase