Purified thioredoxin reductase from O2-sensitive Bifidobacterium bifidum degrades H2O2 by interacting with alkyl hydroperoxide reductase

Genome-Wide Assessment of Stress-Associated Genes in Bifidobacteria

“…A second gene encoding a thioredoxin reductase (TrxR), which has been identified in B. longum subsp. longum NCC2705 and B. bifidum JCM1255, that lacks the N-terminal domain of the disulfide reductase AhpF and seems not to be induced by O 2 stress ( 13 , 25 ) was found to be highly conserved across genomes of species included in this study ( Fig. 1 ).…”

“…Several studies found a positive correlation between O 2 tolerance of Bifidobacterium strains and the ability to detoxify H 2 O 2 ( 20 , 69 , 70 ). Genomics and proteomics have revealed that bifidobacteria lack a gene for NADH peroxidase ( 35 , 78 ) and that an alkyl hydroperoxide reductase subunit C (AhpC) and a thioredoxin reductase-like protein (TrxR), encoded next to AhpC, instead may be responsible for H 2 O 2 decomposition ( 25 , 27 , 35 , 78 ). Our results showed that in 78% of the analyzed species, all strains harbored both an AhpC and TrxR homolog ( Fig.…”

“…S1). Gene regulation, the ratio of different enzymes involved in the ROS-detoxification system ( 25 ), as well as the efficiency of NAD(P)H production driving the oxidative stress response may vary between these Bifidobacterium species. More knowledge on the functions of individual enzymes as well as on O 2 tolerance of individual strains will need to be collected to allow further connections between genotypes and O 2 sensitivity.…”

“…Over the past 2 decades, the morphological, physiological, and metabolic stress responses of bifidobacteria have been increasingly studied to understand the molecular mechanisms that underlie their stability and robustness ( 2 – 32 ). The stress responses of Bifidobacterium strains with diverse stability properties have been assessed, applying traditional methodologies ( 2 – 7 , 14 , 25 , 27 – 32 ) and, more recently, omics technologies ( 8 – 13 , 15 – 24 , 26 ) to characterize and compare strains. The response and tolerance of bifidobacteria to a particular stressor was found to differ significantly among species but also among strains ( 33 , 34 ).…”

Stress Response in Bifidobacteria

“…A thioredoxin reductase-like protein (TrxR; EC 1.8.1.9; encoded by trxB) possessing the Nterminal domain of AhpF is considered to replace the function of AhpF (Fig. 4) (75,111,112). The trxB and ahpC genes are tandemly located in the genome of B. longum NCC2705 and B. bifidum ATCC 29521 (75,112).…”