Role of Alkyl Hydroperoxide Reductase (AhpC) in the Biofilm Formation of Campylobacter jejuni

Abstract

Biofilm formation of Campylobacter jejuni, a major cause of human gastroenteritis, contributes to the survival of this pathogenic bacterium in different environmental niches; however, molecular mechanisms for its biofilm formation have not been fully understood yet. In this study, the role of oxidative stress resistance in biofilm formation was investigated using mutants defective in catalase (KatA), superoxide dismutase (SodB), and alkyl hydroperoxide reductase (AhpC). Biofilm formation was substantially increased in an ahpC mutant compared to the wild type, and katA and sodB mutants. In contrast to the augmented biofilm formation of the ahpC mutant, a strain overexpressing ahpC exhibited reduced biofilm formation. A perR mutant and a CosR-overexpression strain, both of which upregulate ahpC, also displayed decreased biofilms. However, the introduction of the ahpC mutation to the perR mutant and the CosR-overexpression strain substantially enhanced biofilm formation. The ahpC mutant accumulated more total reactive oxygen species and lipid hydroperoxides than the wild type, and the treatment of the ahpC mutant with antioxidants reduced biofilm formation to the wild-type level. Confocal microscopy analysis showed more microcolonies were developed in the ahpC mutant than the wild type. These results successfully demonstrate that AhpC plays an important role in the biofilm formation of C. jejuni.

PerR controls oxidative stress defence and aerotolerance but not motility-associated phenotypes of Campylobacter jejuni

“…Since a fur mutant constitutively expresses iron acquisition systems (Miller et al, 2009;van Vliet et al, 2002), this further complicates interpretation of transcriptomic and proteomic characterization of PerR regulation in C. jejuni. Inactivation of perR results in reduced colonization in chickens, suggesting a role of oxidative stress regulation in intestinal colonization (Palyada et al, 2009), although the reduced motility of the perR mutant reported in this study makes it difficult to distinguish the roles of motility and PerR on colonization.…”

“…Exposure of C. jejuni perR mutants to hydrogen peroxide on discs revealed that the level of peroxide resistance was considerably higher than previously reported, where 3 % hydrogen peroxide was used (Baillon et al, 1999;Flint & Stintzi, 2015;Palyada et al, 2009;van Vliet et al, 1999). Wild-type C. jejuni were sensitive to 5 % H 2 O 2 (Fig.…”

“…When exposed to such conditions, C. jejuni will be under oxidative stress; hence, its ability to deal with such stresses is thought to contribute significantly to its success as a bacterial pathogen. C. jejuni expresses an array of factors combatting oxidative stresses, including several peroxidases (Atack et al, 2008;Baillon et al, 1999;Kendall et al, 2014) and an iron-cofactored superoxide dismutase (Purdy et al, 1999), and the absence of these factors severely affects important aspects of C. jejuni food chain survival and transmission (Oh & Jeon, 2014;Stead & Park, 2000) as well as virulence .…”

“…In C. jejuni, the metalloregulatory proteins Fur and PerR control iron uptake and oxidative stress responses (Holmes et al, 2005;Palyada et al, 2009;van Vliet et al, 1999), with regulation of oxidative stress further complicated by overlapping control circuitry through other regulatory proteins such as CosR and Cj1556 (Dufour et al, 2013;Gundogdu et al, 2011;Hwang et al, 2012;Svensson et al, 2009). Furthermore, DNA-binding by the Dps protein is activated in the presence of iron or hydrogen peroxide, and protects against DNA damage by hydroxyl radicals (Huergo et al, 2013).…”

“…In C. jejuni, PerR was first shown to mediate iron-dependent regulation of catalase (KatA) and alkyl hydroperoxide reductase (AhpC) (van Vliet et al, 1999). Subsequent studies using transcriptional profiling, RNA sequencing (RNA-seq) and chromatin immunoprecipitation using iron, fur and perR mutants have shown that there is significant overlap between the iron, Fur and PerR regulons (Butcher et al, 2012;Butcher & Stintzi, 2013;Holmes et al, 2005;Palyada et al, 2009). PerR has been proposed to modulate its own expression (Kim et al, 2011), while complete derepression of catalase expression was only observed in a fur perR double mutant (van Vliet et al, 1999).…”