Identification of Brucella abortus OxyR and its role in control of catalase expression

Abstract

We report the cloning and sequencing of the Brucella abortus oxyR homolog and provide evidence that the transcription product of this gene binds to the B. abortus catalase promoter region. A gene replacement/deletion Brucella oxyR mutant exhibits increased sensitivity to prolonged exposure to H(2)O(2) and is unable to adapt to H(2)O(2) in the environment.

FIG. 1

Comparison of known OxyR binding sites to sequences in the B. abortus catalase promoter region. The numbers between the sequences indicate the number of nucleotides between the motif sites. Underlined nucleotides match the consensus sequence (24) listed at the top. The fractions of matched nucleotides are at the right. oxyRS, E. coli; katG, E. coli; ahpC, Salmonella enterica serovar Typhimurium; gorA, E. coli; Mu mom, bacteriophage Mu; bacat, B. abortus catalase gene; boxyR, B. abortus oxyR.

FIG. 2

Southwestern blot. B. abortus soluble extract was separated on a sodium dodecyl sulfate–12% (wt/vol) polyacrylamide gel and transferred to nitrocellulose. Membranes were incubated with 5 × 10⁵ cpm of ³²P-labeled catalase promoter probe without (A) or with (B) specific competitor DNA. Arrow, approximate size of the larger band.