In B. fragilis, the TrxB/Trx system is the sole mechanism used to maintain the cellular thiol/disulfide balance and the lack of trxB has a major effect on the bacterial growth, oxidative stress response, increased susceptibility to peroxides and thiol oxidants, and survival in intra‐abdominal experimental infections (Reott, Parker, Rocha & Smith, 2009; Rocha et al., 2007). This evidence concerns the gene TXN and infection.