An Iron-Regulated Alkyl Hydroperoxide Reductase (AhpC) Confers Aerotolerance and Oxidative Stress Resistance to the Microaerophilic Pathogen Campylobacter jejuni

ABSTRACT Microaerophiles like Campylobacter jejuni must resist oxidative stresses during transmission or infection. Growth of C. jejuni 81116 under iron limitation greatly increased the expression of two polypeptides of 26 and 55 kDa. The identification of these proteins by N-terminal amino acid sequencing showed both to be involved in the defense against oxidative stress. The 55-kDa polypeptide was identical to C. jejuni catalase (KatA), whereas the N terminus of the 26-kDa polypeptide was homologous to a 26-kDa Helicobacter pylori protein. The gene encoding theC. jejuni 26-kDa protein was cloned, and the encoded protein showed significant homology to the small subunit of alkyl hydroperoxide reductase (AhpC). The upstream region of ahpCencoded a divergent ferredoxin (fdxA) homolog, whereas downstream sequences contained flhB and motBhomologs, which are involved in flagellar motility. There was no evidence for an adjacent homolog of ahpF, encoding the large subunit of alkyl hydroperoxide reductase. Reporter gene studies showed that iron regulation of ahpC and katA is achieved at the transcriptional level. Insertional mutagenesis of theahpC gene resulted in an increased sensitivity to oxidative stresses caused by cumene hydroperoxide and exposure to atmospheric oxygen, while resistance to hydrogen peroxide was not affected. TheC. jejuni AhpC protein is an important determinant of the ability of this microaerophilic pathogen to survive oxidative and aerobic stress.

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Regulation ofperRExpression by Iron and PerR in Campylobacter jejuni

Journal of Bacteriology ◽

10.1128/jb.05493-11 ◽

2011 ◽

Vol 193 (22) ◽

pp. 6171-6178 ◽

Cited By ~ 17

Author(s):

Minkyeong Kim ◽

Sunyoung Hwang ◽

Sangryeol Ryu ◽

Byeonghwa Jeon

Keyword(s):

Oxidative Stress ◽

Campylobacter Jejuni ◽

Regulatory Region ◽

Transcriptional Level ◽

Mobility Shift ◽

Content Type ◽

Dnase I Footprinting ◽

Transcriptional Changes ◽

Electrophoretic Mobility Shift Assays ◽

Binding Sequence

Campylobacter jejuniis a leading food-borne pathogen causing gastroenteritis in humans. Although OxyR is a widespread oxidative stress regulator in many Gram-negative bacteria,C. jejunilacks OxyR and instead possesses the metalloregulator PerR. Despite the important role played by PerR in oxidative stress defense, little is known about the factors influencingperRexpression inC. jejuni. In this study, aperRpromoter-lacZfusion assay demonstrated that iron significantly reduced the level ofperRtranscription, whereas other metal ions, such as copper, cobalt, manganese, and zinc, did not affectperRtranscription. Notably, aperRmutation substantially increased the level ofperRtranscription and intranscomplementation restored the transcriptional changes, suggestingperRis transcriptionally autoregulated inC. jejuni. In theperRmutant, iron did not repressperRtranscription, indicating the iron dependence ofperRexpression results fromperRautoregulation. Electrophoretic mobility shift assays showed that PerR binds to theperRpromoter, and DNase I footprinting assays identified a PerR binding site overlapping the −35 region of the twoperRpromoters, further supportingperRautoregulation at the transcriptional level. Alignment of the PerR binding sequence in theperRpromoter with the regulatory region of other PerR regulon genes ofC. jejunirevealed a 16-bp consensus PerR binding sequence, which shares high similarities to theBacillus subtilisPerR box. The results of this study demonstrated that PerR directly interacts with theperRpromoter and regulatesperRtranscription and thatperRautoregulation is responsible for the repression ofperRtranscription by iron inC. jejuni.

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Alkyl hydroperoxide reductase from Bacillus aquimaris MKSC 6.2 protects Esherichia coli from oxidative stress

Journal of Basic Microbiology ◽

10.1002/jobm.201500406 ◽

2015 ◽

Vol 56 (7) ◽

pp. 834-837 ◽

Cited By ~ 3

Author(s):

Dessy Natalia ◽

Ozi Jumadila ◽

Irika Devi Anggraini ◽

Febrina Meutia ◽

Fernita Puspasari ◽

...

Keyword(s):

Oxidative Stress ◽

Alkyl Hydroperoxide Reductase ◽

Alkyl Hydroperoxide ◽

Esherichia Coli

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

PLoS ONE ◽

10.1371/journal.pone.0087312 ◽

2014 ◽

Vol 9 (1) ◽

pp. e87312 ◽

Cited By ~ 42

Author(s):

Euna Oh ◽

Byeonghwa Jeon

Keyword(s):

Campylobacter Jejuni ◽

Biofilm Formation ◽

Alkyl Hydroperoxide Reductase ◽

Alkyl Hydroperoxide

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Alkyl Hydroperoxide Reductase Is Required for Helicobacter cinaedi Intestinal Colonization and Survival under Oxidative Stress in BALB/c and BALB/c Interleukin-10−/−Mice

Infection and Immunity ◽

10.1128/iai.05477-11 ◽

2011 ◽

Vol 80 (3) ◽

pp. 921-928 ◽

Cited By ~ 20

Author(s):

Nisanart Charoenlap ◽

Zeli Shen ◽

Megan E. McBee ◽

Suresh Muthupalani ◽

Gerald N. Wogan ◽

...

Keyword(s):

Oxidative Stress ◽

Serum Levels ◽

Interleukin 10 ◽

Intestinal Bacterium ◽

Bacterial Survival ◽

Alkyl Hydroperoxide Reductase ◽

Content Type ◽

Helicobacter Cinaedi ◽

Alkyl Hydroperoxide

Helicobacter cinaedi, a common human intestinal bacterium, has been implicated in various enteric and systemic diseases in normal and immunocompromised patients. Protection against oxidative stress is a crucial component of bacterium-host interactions. Alkyl hydroperoxide reductase C (AhpC) is an enzyme responsible for detoxification of peroxides and is important in protection from peroxide-induced stress.H. cinaedipossesses a singleahpC, which was investigated with respect to its role in bacterial survival during oxidative stress. TheH. cinaedi ahpCmutant had diminished resistance to organic hydroperoxide toxicity but increased hydrogen peroxide resistance compared with the wild-type (WT) strain. The mutant also exhibited an oxygen-sensitive phenotype and was more susceptible to killing by macrophages than the WT strain.In vivoexperiments in BALB/c and BALB/c interleukin-10 (IL-10)−/−mice revealed that the cecal colonizing ability of theahpCmutant was significantly reduced. The mutant also had diminished ability to induce bacterium-specific immune responsesin vivo, as shown by immunoglobulin (IgG2a and IgG1) serum levels. Collectively, these data suggest thatH. cinaedi ahpCnot only contributes to protecting the organism against oxidative stress but also alters its pathogenic propertiesin vivo.

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