Role of the thioredoxin system and the thiol-peroxidases Tpx and Bcp in mediating resistance to oxidative and nitrosative stress in Helicobacter pylori

• Published in: Microbiology (Society for General Microbiology) Vol. 149; no. 1; pp. 121 - 129
• Main Authors: Comtois, Spencer L, Gidley, Mark D, Kelly, David J
• Format: Journal Article
• Language: English
• Published: Reading Soc General Microbiol 01-01-2003; Society for General Microbiology
• Subjects: Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; bcp gene; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Helicobacter pylori; Helicobacter pylori - drug effects; Helicobacter pylori - growth & development; Helicobacter pylori - physiology; Humans; Membrane Proteins - genetics; Membrane Proteins - metabolism; Microbiology; Mutagenesis; Mutation; Nitric Oxide - pharmacology; Oxidative Stress; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Peroxidases - genetics; Peroxidases - metabolism; Peroxides - pharmacology; Peroxiredoxins; Superoxides - pharmacology; Thioredoxin; Thioredoxins - genetics; Thioredoxins - metabolism; tpx gene; Trx1 protein; Trx2 protein; trxA1 gene; trxA2 gene; Resistance; Oxidative stress; Spirillales; Helicobacter pylori; Peroxidases; Enzyme; Sulfoprotein; Nitric oxide; Spirillaceae; Bacteria; Oxidoreductases; Thioredoxin
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.25896-0

Department of Molecular Biology & Biotechnology, University of Sheffield, Firth Court, Western Bank, Sheffield S10 2TN, UK
Correspondence David J. Kelly d.kelly{at}sheffield.ac.uk
Helicobacter pylori possesses two distinct thioredoxin proteins (Trx1 and Trx2) which may play important roles in the ability of this bacterium to survive oxidative stress. Trx1 has previously been shown to be an electron donor in vitro for alkyl-hydroperoxide reductase (AhpC), one of three members of the peroxiredoxin family of antioxidant peroxidases present in H. pylori . In this study, mutants in the trxA1 and trxA2 genes encoding Trx1 and Trx2, respectively, and in the tpx and bcp genes, which encode the remaining two members of the H. pylori peroxiredoxin family, were constructed in order to determine their roles in resistance to damage by reactive oxygen and nitrogen species. Mutation of trxA1 led to a pronounced increase in sensitivity to oxygen, hydrogen peroxide and the superoxide generator paraquat, as well as to the nitric oxide (NO) releasers sodium nitroprusside (SNP) and S -nitrosoglutathione (GSNO), consistent with an in vivo role for Trx1 as a reductant for AhpC. A trxA2 single mutant grew normally in an atmosphere of 2 % (v/v) O 2 but grew very poorly in 10 % (v/v) O 2 . It showed slight increases in killing by hydrogen peroxide, paraquat, SNP and GSNO compared to the wild-type, but was significantly more sensitive to cumene hydroperoxide in disc-diffusion assays. A trxA1 trxA2 double mutant was very sensitive to all of the oxidative and nitrosative stresses applied. Comparison of the phenotypes of the tpx and bcp mutants showed that Tpx plays a significant role in peroxide and superoxide resistance in H. pylori , while the role of Bcp is minimal. No evidence was obtained for a role for either Tpx or Bcp in resistance to the toxic effects of NO. The results show that a functional thioredoxin system is necessary for both oxidative and nitrosative stress resistance in H. pylori but, surprisingly, is not essential for viability despite the absence of glutathione and a glutaredoxin system in this bacterium.
Abbreviations: GSNO, S -nitrosoglutathione; SNP, sodium nitroprusside
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