Regulation of Brucella abortus Catalase

Abstract

All aerobic organisms have mechanisms that protect against oxidative compounds. Catalase, peroxidase, superoxide dismutase, glutathione, and thioredoxin are widely distributed in many taxa and constitute elements of a nearly ubiquitous antioxidant metabolic strategy. Interestingly, the regulatory mechanisms that control these elements are rather different depending on the nature of the oxidative stress and the organism. Catalase is well documented to play an important role in protecting cells from oxidative stress. In particular, pathogenic bacteria seem to use this enzyme as a defensive tool against attack by the host. To investigate the significance of catalase in hostile environments, we made catalase deletion mutations in two different B. abortus strains and used two-dimensional gel analysis, survival tests, and adaptation experiments to explore the behavior and role of catalase under several oxidative stress conditions. These studies show that B. abortus strains that do not express catalase activity exhibit increased sensitivity to hydrogen peroxide. We also demonstrate that catalase expression is regulated in this species, and that preexposure to a sublethal concentration of hydrogen peroxide allows B. abortus to adapt so as to survive subsequent exposure to higher concentrations of hydrogen peroxide.

The katA Catalase Gene Is Regulated by OxyR in both Free-Living and Symbiotic Sinorhizobium meliloti

“…The position of oxyR is very variable in the different bacterial genomes, but it is often next to a gene involved in oxidative stress protection and regulated by OxyR: for example, ahpC in Mycobacterium tuberculosis (7) and Xanthomonas campestris pv. phaseoli (25), dps in Bacteroides fragilis (32), oxyS in E. coli (4), recG in Pseudomonas aeruginosa (28), kat in B. abortus (17). Similar genomic relationships between oxyR and catalase genes are observed for most members of the Rhizobiales studied so far, such as S. meliloti, Agrobacterium tumefaciens, B. abortus, Mesorhizobium loti, Rhizobium etli, and Rhizobium leguminosarum bv.…”

“…The oxyR homologous gene in S. meliloti is located 193 bp upstream of and in the strand opposite to katA. The regulation of an HPII-like catalase by OxyR has been described for Brucella abortus only (17). The alignment of the oxyR-katA intergenic regions from S. meliloti and B. abortus (Fig.…”

Identification of Brucella abortus OxyR and Its Role in Control of Catalase Expression

“…Brucella abortus has a single hydroperoxidase, a true catalase, which is expressed in the periplasm (17). In previous studies (10,11), it was shown that Brucella catalase is regulated at the transcriptional level.…”

Comparative Study of the Roles of AhpC and KatE as Respiratory Antioxidants inBrucella abortus2308

“…Although this protein does not possess a standard export signal sequence (63) or a predicted twin arginine transport signal sequence (data not shown), cell fractionation studies with the appropriate controls indicate that this protein resides in the periplasmic compartment (63). B. abortus and Brucella melitensis katE mutants exhibit increased sensitivity to H 2 O 2 compared to their parental strains in in vitro assays (21,33). A B. melitensis katE mutant retains its virulence in experimentally infected goats (21), and B. abortus katE mutants display wild-type virulence in the mouse model (59).…”