Oxidative stress defense mechanisms to counter iron-promoted DNA damage in Helicobacter pylori.

Iron, a key element in Fenton chemistry, causes oxygen-related toxicity to cells of most living organisms. Helicobacter pylori is a microaerophilic bacterium that infects human gastric mucosa and causes a series of gastric diseases. Exposure of H.

Up-expression of NapA and other oxidative stress proteins is a compensatory response to loss of major Helicobacter pylori stress resistance factors.

Twenty-six Helicobacter pylori targeted mutant strains with deficiencies in oxidative stress combating proteins, including 12 double mutant strains were analyzed via physiological and proteomic approaches to distinguish the major expression changes caused by the mutations. Mutations were introduced into both a Mtz(S) and a Mtz(R) strain background. Most of the mutations caused increased growth sensitivity of the strains to oxygen, and they all exhibited clear compensatory up-expression of oxidative stress resistance proteins enabling survival of the bacterium.

Contribution of the Helicobacter pylori thiol peroxidase bacterioferritin comigratory protein to oxidative stress resistance and host colonization.

Peroxiredoxins, the enzymes that catalyze the reduction of hydrogen peroxide and organic hydroperoxides, are ubiquitous proteins that protect organisms from damage by reactive oxygen species. Helicobacter pylori contains three members of the peroxiredoxin family: AhpC (alkyl hydroperoxide reductase), Tpx (thiol-specific peroxidase), and bacterioferritin comigratory protein (BCP). In this study, we characterized H.

Role of a bacterial organic hydroperoxide detoxification system in preventing catalase inactivation.

In the gastric pathogen Helicobacter pylori, catalase (KatA) and alkyl hydroperoxide reductase (AhpC) are two highly abundant enzymes that are crucial for oxidative stress resistance and survival of the bacterium in the host. Here we report a connection unidentified previously between the two stress resistance enzymes. We observed that the catalase in ahpC mutant cells in comparison with the parent strain is inactivated partially (approximately 50%).

Association of Helicobacter pylori antioxidant activities with host colonization proficiency.

To assess the importance of two separate antioxidant activities in Helicobacter pylori, we tested the abilities of strains with mutations in either tpx (encoding thiolperoxidase) or ahpC (encoding alkyl hydroperoxide reductase [AhpC]) to colonize the stomachs of mice. The tpx strain was clearly more sensitive than the parent strain to both oxygen and cumene hydroperoxide. The strain colonized only 5% of the inoculated mice.

Oxidative-stress resistance mutants of Helicobacter pylori.

Within a large family of peroxidases, one member that catalyzes the reduction of organic peroxides to alcohols is known as alkyl hydroperoxide reductase, or AhpC. Gene disruption mutations in the gene encoding AhpC of Helicobacter pylori (ahpC) were generated by screening transformants under low-oxygen conditions. Two classes of mutants were obtained.