Affiliation:
1. Department of Microbiology and Immunology, East Carolina University School of Medicine, Greenville, North Carolina 27834
Abstract
ABSTRACT
Brucella
strains are exposed to potentially toxic levels of H
2
O
2
both as a consequence of their aerobic metabolism and through the respiratory burst of host phagocytes. To evaluate the relative contributions of the sole catalase KatE and the peroxiredoxin AhpC produced by these strains in defense against H
2
O
2
-mediated toxicity, isogenic
katE
,
ahpC
, and
katE ahpC
mutants were constructed and the phenotypic properties of these mutants compared with those of the virulent parental strain
B. abortus
2308. The results of these studies indicate that AhpC is the primary detoxifier of endogenous H
2
O
2
generated by aerobic metabolism. KatE, on the other hand, plays a major role in scavenging exogenous and supraphysiologic levels of H
2
O
2
, although this enzyme can play a supporting role in the detoxification of H
2
O
2
of endogenous origin if AhpC is absent.
B. abortus ahpC
and
katE
mutants exhibit wild-type virulence in C57BL/6 and BALB/c mice, but the
B. abortus ahpC katE
double mutant is extremely attenuated, and this attenuation is not relieved in derivatives of C57BL/6 mice that lack NADPH oxidase (cybb) or inducible nitric oxide synthase (Nos2) activity. These experimental findings indicate that the generation of endogenous H
2
O
2
represents a relevant environmental stress that
B. abortus
2308 must deal with during its residence in the host and that AhpC and KatE perform compensatory roles in detoxifying this metabolic H
2
O
2
.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
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