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Role of the ArcAB two-component system in the resistance of Escherichia coli to reactive oxygen stress.

Loui C, Chang AC, Lu S - BMC Microbiol. (2009)

Bottom Line: Our results demonstrated that both ArcA and ArcB were necessary for resistance to hydrogen peroxide (H2O2), a type of ROS, and their function in this resistance was independent from H2O2 scavenge.An abundant protein flagellin was elevated at both the protein and mRNA levels in the DeltaarcA mutant as compared to the wild type E. coli, and deletion of flagellin restored the resistance of the DeltaarcA mutant to H2O2.The resistance of the DeltaarcA mutant E. coli to H2O2 can also be restored by amino acid supplementation, suggesting that a deficiency in amino acid and/or protein synthesis in the mutant contributed to its susceptibility to H2O2, which is consistent with the notion that protein synthesis is necessary for ROS resistance.

View Article: PubMed Central - HTML - PubMed

Affiliation: Program in Infectious Diseases and Immunity, School of Public Health, University of California, Berkeley, CA 94720, USA. csloui@berkeley.edu

ABSTRACT

Background: The global regulatory system ArcAB controls the anaerobic growth of E. coli, however, its role in aerobic conditions is not well characterized. We have previously reported that ArcA was necessary for Salmonella to resist reactive oxygen species (ROS) in aerobic conditions.

Results: To investigate the mechanism of ROS resistance mediated by ArcAB, we generated deletion mutants of ArcA and ArcB in E. coli. Our results demonstrated that both ArcA and ArcB were necessary for resistance to hydrogen peroxide (H2O2), a type of ROS, and their function in this resistance was independent from H2O2 scavenge. Mutagenesis analysis of ArcA indicated that ROS resistance was mediated through a distinct signaling pathway from that used in anaerobic conditions. An abundant protein flagellin was elevated at both the protein and mRNA levels in the DeltaarcA mutant as compared to the wild type E. coli, and deletion of flagellin restored the resistance of the DeltaarcA mutant to H2O2. The resistance of the DeltaarcA mutant E. coli to H2O2 can also be restored by amino acid supplementation, suggesting that a deficiency in amino acid and/or protein synthesis in the mutant contributed to its susceptibility to H2O2, which is consistent with the notion that protein synthesis is necessary for ROS resistance.

Conclusion: Our results suggest that in addition to its role as a global regulator for anaerobic growth of bacteria, ArcAB system is also important for bacterial resistance to ROS in aerobic conditions, possibly through its influence on bacterial metabolism, especially amino acid and/or protein assimilation and synthesis.

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The ArcAB system is dispensable for H2O2 scavenge. The ΔarcA (square), ΔarcB (triangle) mutant and the wild type E. coli K12 (diamond) was cultured in LB broth supplemented with 2 mM of H2O2 at 37°C with shaking. Bacterial concentration and the H2O2 concentration were measured at various time points. The H2O2 scavenge was measured as the decrease of H2O2 concentration per 107 c.f.u. bacteria. A control sample without bacteria (cross) was included to monitor any possible spontaneous degradation of H2O2. The experiment was repeated at least three times, and data from one representative assay performed in duplicates were shown. Error bars indicate standard deviation and sometimes fall within the data label.
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Figure 2: The ArcAB system is dispensable for H2O2 scavenge. The ΔarcA (square), ΔarcB (triangle) mutant and the wild type E. coli K12 (diamond) was cultured in LB broth supplemented with 2 mM of H2O2 at 37°C with shaking. Bacterial concentration and the H2O2 concentration were measured at various time points. The H2O2 scavenge was measured as the decrease of H2O2 concentration per 107 c.f.u. bacteria. A control sample without bacteria (cross) was included to monitor any possible spontaneous degradation of H2O2. The experiment was repeated at least three times, and data from one representative assay performed in duplicates were shown. Error bars indicate standard deviation and sometimes fall within the data label.

Mentions: To determine the mechanism of how the ArcAB system is involved in H2O2 resistance, we analyzed the H2O2 scavenging activity of the ΔarcA and ΔarcB mutant of E. coli K12, since a defect in H2O2 scavenging activity may lead to the susceptibility to H2O2. The overnight culture was diluted in LB containing 2 mM of H2O2, and the concentration of the residual H2O2 was measured after various incubation period. The scavenge of H2O2 was measured as the reduction in H2O2 concentration over the incubation period. Our results indicate that both ΔarcA and ΔarcB mutants scavenged H2O2 normally as compared to the wild type E. coli K12., and no deficiency was observed (Figure 2).


Role of the ArcAB two-component system in the resistance of Escherichia coli to reactive oxygen stress.

Loui C, Chang AC, Lu S - BMC Microbiol. (2009)

The ArcAB system is dispensable for H2O2 scavenge. The ΔarcA (square), ΔarcB (triangle) mutant and the wild type E. coli K12 (diamond) was cultured in LB broth supplemented with 2 mM of H2O2 at 37°C with shaking. Bacterial concentration and the H2O2 concentration were measured at various time points. The H2O2 scavenge was measured as the decrease of H2O2 concentration per 107 c.f.u. bacteria. A control sample without bacteria (cross) was included to monitor any possible spontaneous degradation of H2O2. The experiment was repeated at least three times, and data from one representative assay performed in duplicates were shown. Error bars indicate standard deviation and sometimes fall within the data label.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2748088&req=5

Figure 2: The ArcAB system is dispensable for H2O2 scavenge. The ΔarcA (square), ΔarcB (triangle) mutant and the wild type E. coli K12 (diamond) was cultured in LB broth supplemented with 2 mM of H2O2 at 37°C with shaking. Bacterial concentration and the H2O2 concentration were measured at various time points. The H2O2 scavenge was measured as the decrease of H2O2 concentration per 107 c.f.u. bacteria. A control sample without bacteria (cross) was included to monitor any possible spontaneous degradation of H2O2. The experiment was repeated at least three times, and data from one representative assay performed in duplicates were shown. Error bars indicate standard deviation and sometimes fall within the data label.
Mentions: To determine the mechanism of how the ArcAB system is involved in H2O2 resistance, we analyzed the H2O2 scavenging activity of the ΔarcA and ΔarcB mutant of E. coli K12, since a defect in H2O2 scavenging activity may lead to the susceptibility to H2O2. The overnight culture was diluted in LB containing 2 mM of H2O2, and the concentration of the residual H2O2 was measured after various incubation period. The scavenge of H2O2 was measured as the reduction in H2O2 concentration over the incubation period. Our results indicate that both ΔarcA and ΔarcB mutants scavenged H2O2 normally as compared to the wild type E. coli K12., and no deficiency was observed (Figure 2).

Bottom Line: Our results demonstrated that both ArcA and ArcB were necessary for resistance to hydrogen peroxide (H2O2), a type of ROS, and their function in this resistance was independent from H2O2 scavenge.An abundant protein flagellin was elevated at both the protein and mRNA levels in the DeltaarcA mutant as compared to the wild type E. coli, and deletion of flagellin restored the resistance of the DeltaarcA mutant to H2O2.The resistance of the DeltaarcA mutant E. coli to H2O2 can also be restored by amino acid supplementation, suggesting that a deficiency in amino acid and/or protein synthesis in the mutant contributed to its susceptibility to H2O2, which is consistent with the notion that protein synthesis is necessary for ROS resistance.

View Article: PubMed Central - HTML - PubMed

Affiliation: Program in Infectious Diseases and Immunity, School of Public Health, University of California, Berkeley, CA 94720, USA. csloui@berkeley.edu

ABSTRACT

Background: The global regulatory system ArcAB controls the anaerobic growth of E. coli, however, its role in aerobic conditions is not well characterized. We have previously reported that ArcA was necessary for Salmonella to resist reactive oxygen species (ROS) in aerobic conditions.

Results: To investigate the mechanism of ROS resistance mediated by ArcAB, we generated deletion mutants of ArcA and ArcB in E. coli. Our results demonstrated that both ArcA and ArcB were necessary for resistance to hydrogen peroxide (H2O2), a type of ROS, and their function in this resistance was independent from H2O2 scavenge. Mutagenesis analysis of ArcA indicated that ROS resistance was mediated through a distinct signaling pathway from that used in anaerobic conditions. An abundant protein flagellin was elevated at both the protein and mRNA levels in the DeltaarcA mutant as compared to the wild type E. coli, and deletion of flagellin restored the resistance of the DeltaarcA mutant to H2O2. The resistance of the DeltaarcA mutant E. coli to H2O2 can also be restored by amino acid supplementation, suggesting that a deficiency in amino acid and/or protein synthesis in the mutant contributed to its susceptibility to H2O2, which is consistent with the notion that protein synthesis is necessary for ROS resistance.

Conclusion: Our results suggest that in addition to its role as a global regulator for anaerobic growth of bacteria, ArcAB system is also important for bacterial resistance to ROS in aerobic conditions, possibly through its influence on bacterial metabolism, especially amino acid and/or protein assimilation and synthesis.

Show MeSH
Related in: MedlinePlus