Thioredoxin Reductase Is Essential for Thiol/Disulfide Redox Control and Oxidative Stress Survival of the Anaerobe Bacteroides fragilis

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 H 2 O 2 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.

Adaptation of Porphyromonas gingivalis to microaerophilic conditions involves increased consumption of formate and reduced utilization of lactate

“…The thioredoxin system (thioredoxin, thioredoxin reductase and NADPH) is a disulfide-reducing system present in a variety of bacteria and has been demonstrated to protect cells against oxidative stress. Our results are also consistent with other reports that demonstrate induction of these genes upon exposure to oxygen in P. gingivalis (Diaz et al, 2006;Meuric et al, 2008) as well as in the related bacterium B. fragilis (Rocha et al, 2007).…”

Characterization of the Bacteroides fragilis bfr Gene Product Identifies a Bacterial DPS-Like Protein and Suggests Evolutionary Links in the Ferritin Superfamily

“…Mutant strains were constructed by allelic exchange (see Fig. S1 in the supplemental material) as described previously using the suicide vector pFD516 and the PCR primers described in Table S1 in the supplemental material (53). For the construction of mutant BER63, 400 bp from the central portion of the ftnA gene was deleted and replaced with a 2.2-kb tetQ gene fragment.…”

Thioredoxin system – a novel therapeutic target

“…Similarly as in many non-pathogenic organisms' genomes, also in pathogens have been identified a number of Trx and TrxR. For example, Trx system is a major thiol-disulfide redox system in gram-negative, opportunistic pathogen B. fragilis (Rocha et al 2007) and contains six genes encoding homologues of Trx and one gene for TrxR (Reott et al 2009). Recently studies revealed that not all Trx proteins are still active and providing an active protection.…”