Thioredoxin Reductase Is Essential for Thiol/Disulfide Redox Control and Oxidative Stress Survival of the Anaerobe Bacteroides fragilis
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Date
2007-11
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Authors
Rocha, Edson R.
Tzianabos, Arthur O.
Smith, C. Jeffrey
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Publisher
East Carolina University
Abstract
Results of this study showed that the anaerobic, opportunistic pathogen Bacteroides fragilis lacks the
glutathione/glutaredoxin redox system and possesses an extensive number of putative thioredoxin (Trx)
orthologs. Analysis of the genome sequence revealed six Trx orthologs and an absence of genes required for
synthesis of glutathione and glutaredoxins. In addition, it was shown that the thioredoxin reductase (TrxB)/Trx
system is the major or sole redox system for thiol/disulfide cellular homeostasis in this anaerobic bacterium.
Expression of the B. fragilis trxB gene was induced following treatment with diamide or H2O2 or exposure to
oxygen. This inducible trxB expression was OxyR independent. Northern blot hybridization analysis showed
that the trxB mRNA was cotranscribed with lolA as a bicistronic transcript or was present as a monocistronic
transcript that was also highly induced under the same conditions. The role of LolA, a prokaryotic periplasmic
lipoprotein-specific molecular chaperone in the thiol/disulfide redox system, is unknown. A trxB deletion
mutant was more sensitive to the effects of diamide and oxygen than the parent strain. In addition, the trxB
mutant was unable to grow in culture media without addition of a reductant. Furthermore, the trxB mutant was
not able to induce intraabdominal abscess formation in a mouse model, whereas the parent strain was. Taken
together, these data strongly suggest that TrxB/Trx is the major, if not the sole, thiol/disulfide redox system in
this anaerobe required for survival and abscess formation in a peritoneal cavity infection model. Originally published Journal of Bacteriology, Vol. 189, No. 22, Nov. 2007
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Citation
Journal of Bacteriology; 189:22 p. 8015-8023