Catalases Promote Resistance of Oxidative Stress in Vibrio cholerae

Abstract

Oxidative stress is a major challenge faced by bacteria. Many bacteria control oxidative stress resistance pathways through the transcriptional regulator OxyR. The human pathogen Vibrio cholerae is a Gram-negative bacterium that is the causative agent of cholera. V. cholerae lives in both aquatic environments and human small intestines, two environments in which it encounters reactive oxygen species (ROS). To study how V. cholerae responds to oxidative stress, we constructed an in-frame oxyR deletion mutant. We found that this mutant was not only sensitive to H2O2, but also displayed a growth defect when diluted in rich medium. Further study showed that two catalases, KatG and KatB, either when expressed in living cells, present in culture supernatants, or added as purified recombinant proteins, could rescue the oxyR growth defect. Furthermore, although it could colonize infant mouse intestines similar to that of wildtype, the oxyR mutant was defective in zebrafish intestinal colonization. Alternatively, co-infection with wildtype, but not katG-katB deletion mutants, greatly enhanced oxyR mutant colonization. Our study suggests that OxyR in V. cholerae is critical for antioxidant defense and that the organism is capable of scavenging environmental ROS to facilitate population growth.

OxyR2 Modulates OxyR1 Activity and Vibrio cholerae Oxidative Stress Response

“…The expression of both prxA and katG was also significantly higher in the presence of H 2 O 2 in an OxyR1-dependent manner (Fig. 3C), confirming previous findings (15,17). Both prxA and katG transcriptome levels were significantly higher in the ΔoxyR2 mutants, either in the absence or in the presence of H 2 O 2 , again implying that OxyR2 may negatively affect OxyR1-activated gene expression.…”

“…Several bacteria have AhpC, although not all have the reducing partner AhpF (e.g., Helicobacter pylori and Salmonella enterica serovar Typhimurium) (10). In V. cholerae, OxyR positively activates genes for peroxiredoxin PrxA and DPS (DNA-binding protein from starved cells), and these genes are critical for V. cholerae oxidative stress resistance (15,16). In this study, we sought to find additional peroxiredoxins that may be involved in V. cholerae oxidative stress resistance.…”

The Na + -Translocating NADH:Quinone Oxidoreductase Enhances Oxidative Stress in the Cytoplasm of Vibrio cholerae

“…cholerae ⌬oxyR is hypersensitive to overexpression of Na ؉ -NQR. OxyR is a transcriptional regulator that is activated by H 2 O 2 to promote the synthesis of ROS protection enzymes like catalase under conditions of oxidative stress (47,48). We showed that the Na ϩ -NQR is a source for O 2˙Ϫ and H 2 O 2 and reasoned that V. cholerae critically depended on its ROS protection enzymes, especially under conditions of overexpression of Na ϩ -NQR, which leads to increased ROS formation (Table 2).…”

Legionella pneumophila OxyR Is a Redundant Transcriptional Regulator That Contributes to Expression Control of the Two-Component CpxRA System

“…Interestingly, the recovery of a ΔoxyR Lp L. pneumophila mutant on laboratory medium did not require the addition of the catalase enzyme to achieve isolated single colonies. Elsewhere, deletion of oxyR in the Gram-negative bacteria Pseudomonas aeruginosa, Haemophilus influenzae, Shigella flexneri, and Vibrio cholerae resulted in a lack of isolated colonies when grown on rich laboratory medium, as well as growth defects in corresponding broth media that could only be rescued by the addition of catalase or expression of factors that alleviate oxidative stress (59)(60)(61)(62). However, the inclusion of ␣-ketoglutarate in buffered charcoal yeast extract (BCYE) medium may have assisted in combatting reactive oxygen species (ROS), allowing the isolation of the oxyR Lp mutant strain.…”