Effects of peroxides on susceptibilities of Escherichia coli and Mycobacterium smegmatis to isoniazid

Rosner, Judah L.; Storz, Gisela

doi:10.1128/aac.38.8.1829

Cited by 37 publications

(29 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…In contrast, the introduction of katG (LC80), katE (HDO3), or both katG and katE (LC84) mutations did not increase ␤-galactosidase activity at all (0.04 Ϯ 0.01, 0.03 Ϯ 0.01, and 0.04 Ϯ 0.01 U/mg, respectively). These results agreed with the observations of Rosner and Storz (27) and Ritz et al (25a).…”

Section: Resultssupporting

confidence: 83%

Alkyl Hydroperoxide Reductase Is the Primary Scavenger of Endogenous Hydrogen Peroxide in Escherichia coli

2001

View full text Add to dashboard Cite

Hydrogen peroxide is generated during aerobic metabolism and is capable of damaging critical biomolecules. However, mutants of Escherichia coli that are devoid of catalase typically exhibit no adverse phenotypes during growth in aerobic media. We discovered that catalase mutants retain the ability to rapidly scavenge H 2 O 2 whether it is formed internally or provided exogenously. Analysis of candidate genes revealed that the residual activity is due to alkyl hydroperoxide reductase (Ahp

show abstract

Section: Resultssupporting

confidence: 83%

Alkyl Hydroperoxide Reductase Is the Primary Scavenger of Endogenous Hydrogen Peroxide in Escherichia coli

2001

View full text Add to dashboard Cite

show abstract

“…Our finding that the ahpC-1613 insertion mutation derepresses the peroxide regulon sug-gests that H 2 O 2 may not be the only inducer. A similar inference can be drawn from the observation that ahpC mutations in E. coli lead to high-level transcription of the oxyRregulated gene oxyS, and transcription is further elevated in the katG ahpCF double mutant (31). Although AhpCF is reported to reduce H 2 O 2 in vitro (28,30), our measurements of H 2 O 2 consumption in wild-type and katA mutant strains suggest that KatA accounts for Ͼ95% of the H 2 O 2 -decomposing activity in vivo (data not shown).…”

Section: Discussionmentioning

confidence: 93%

Mutation of the Bacillus subtilis alkyl hydroperoxide reductase (ahpCF) operon reveals compensatory interactions among hydrogen peroxide stress genes

1996

View full text Add to dashboard Cite

In Bacillus subtilis, hydrogen peroxide induces the synthesis of catalase (KatA), alkyl hydroperoxide reductase (AhpCF), and a DNA-binding protein of the Dps family (MrgA). KatA, AhpCF, heme biosynthesis enzymes, and MrgA are also induced upon entry into stationary phase under conditions of iron and manganese limitation. In an effort to define the peroxide regulon repressor, PerR, we used mini-Tn10 mutagenesis to identify loci affecting the regulation of mrgA. From this screen, we isolated two mini-Tn10 insertions in ahpC, the gene encoding the small subunit of AhpCF, that increase the transcription of mrgA-lacZ even in ironsupplemented minimal medium. Indeed, these ahpC::Tn10 insertions lead to elevated expression from all peroxide regulon promoters, including those for mrgA, katA, hemAXCDBL, and ahpCF. As a result, the ahpC::Tn10 mutants display an increased resistance to H 2 O 2 . The ahpCF promoter region contains three sequences similar to the peroxide regulon consensus operator (per box). We demonstrate that the ability of ahpC::Tn10 mutations to derepress mrgA requires aerobic growth. In contrast, a second distinct trans-acting regulatory mutation bypasses this requirement for aerobic growth. Since the peroxide regulon is activated in the absence of AhpCF, which degrades alkyl hydroperoxides, we propose that organic hydroperoxides may be physiologically relevant inducers in vivo.

show abstract

“…Such an increased resistance due to elevated expression from all peroxide regulon promoters has been reported for a Bacillus subtilis ahpC mutant (7). Similarly, the lack of AhpCAhpF peroxidase expression in E. coli has been shown to lead to constitutive OxyR activation due to the accumulation of endogenous oxidants (43). Somewhat surprising was the hypersusceptibility to H 2 O 2 of strains harboring the ahpCF genes on a multicopy plasmid.…”

Section: Discussionmentioning

confidence: 98%

Role of the Pseudomonas aeruginosa oxyR-recG Operon in Oxidative Stress Defense and DNA Repair: OxyR-Dependent Regulation of katB-ankB , ahpB , and ahpC-ahpF

et al. 2000

View full text Add to dashboard Cite

Pseudomonas aeruginosa possesses an extensive armament of genes involved in oxidative stress defense, including katB-ankB, ahpB, and ahpC-ahpF. Transcription of these genes was regulated in response to H 2 O 2 , paraquat, or organic peroxides. Expression of katB-lacZ and the observed KatB catalase levels in P. aeruginosa PAO1 were induced up to 250-fold after exposure to oxidative stress-generating compounds. Also, ahpB-lacZ and ahpC-lacZ expression was 90-and 3-fold higher, respectively, upon exposure to paraquat. The dose-and time-response curves revealed that 1 M paraquat was sufficient for half-maximal activation of each reporter fusion within 5 min of exposure. Expression of these genes was not observed in a ⌬oxyR mutant, indicating that OxyR was essential for this response. The transcriptional start sites of katB-ankB, ahpB, and ahpC-ahpF were mapped, putative OxyR-binding sites were identified upstream of the ؊35 promoter elements, and direct binding of purified OxyR protein to these target promoters was demonstrated. The oxyR mutant was hypersusceptible to oxidative stress-generating agents, including H 2 O 2 and paraquat, in spite of total KatA catalase activity being comparable to that of the wild type. The oxyR phenotype was fully complemented by a plasmid containing the oxyR gene, while any of the katB, ahpB, or ahpCF genes alone resulted in only marginal complementation. Increased katB-lacZ expression and higher KatB catalase levels were detected in a ⌬ahpCF background compared to wild-type bacteria, suggesting a compensatory function for KatB in the absence of AhpCF. In P. aeruginosa, oxyR is located upstream of recG, encoding a putative DNA repair enzyme. oxyR-lacZ and recG-lacZ reporter activities and oxyR-recG mRNA analysis showed that oxyR and recG are organized in an operon and expressed constitutively with regard to oxidative stress from a single promoter upstream of oxyR. Mutants affected in recG but not oxyR were dramatically impaired in DNA damage repair as measured by sensitivity to UV irradiation. In conclusion, we present evidence that the oxyR-recG locus is essential for oxidative stress defense and for DNA repair.Pseudomonas aeruginosa generates metabolic energy primarily through aerobic respiration. This process, involving a four-electron reduction of molecular oxygen (O 2 ) to water, can be potentially dangerous to the cell. Specifically, aberrant electron flow from the electron transport chain or cellular redox enzymes to O 2 can lead to the production of reactive oxygen intermediates (ROIs). These include superoxide (O 2 Ϫ ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radical (HO ⅐ ). Furthermore, bacteria can be exposed to exogenous ROIs, especially during infection of humans, where phagocytes (e.g., neutrophils) mount a dramatic oxygen-dependent antimicrobial response (16, 38). The unchecked production or accumulation of these species can lead to cell damage, mutations, or death. The generation of HO ⅐ , the most destructive of the above-mentioned compounds, is in part dependent...

show abstract

Effects of peroxides on susceptibilities of Escherichia coli and Mycobacterium smegmatis to isoniazid

Cited by 37 publications

References 16 publications

Alkyl Hydroperoxide Reductase Is the Primary Scavenger of Endogenous Hydrogen Peroxide in Escherichia coli

Alkyl Hydroperoxide Reductase Is the Primary Scavenger of Endogenous Hydrogen Peroxide in Escherichia coli

Mutation of the Bacillus subtilis alkyl hydroperoxide reductase (ahpCF) operon reveals compensatory interactions among hydrogen peroxide stress genes

Role of the Pseudomonas aeruginosa oxyR-recG Operon in Oxidative Stress Defense and DNA Repair: OxyR-Dependent Regulation of katB-ankB , ahpB , and ahpC-ahpF

Contact Info

Product

Resources

About