Thioredoxin reductase is a key factor in the oxidative stress response of Lactobacillus plantarum WCFS1

ABSTRACT: BACKGROUND: Thioredoxin (TRX) is a powerful disulfide oxido-reductase that catalyzes a wide spectrum of redox reactions in the cell. The aim of this study is to elucidate the role of the TRX system in the oxidative stress response in Lactobacillus plantarum WCFS1. RESULTS: We have identified the trxB1-encoded thioredoxin reductase (TR) as a key enzyme in the oxidative stress response of Lactobacillus plantarum WCFS1. Overexpression of the trxB1 gene resulted in a 3-fold higher TR activity in comparison to the wild-type strain. Higher TR activity was associated with an increased resistance towards oxidative stress. Gene expression profiling showed significant differential expression of 27 genes in the trxB1-overexpression strain. We further determined the global transcriptional response to hydrogen peroxide stress in the trxB1-overexpression and wild-type strains grown in continuous cultures. Over expression of trxB1 was found to activate genes associated with DNA repair and stress mechanisms as well as genes associated with the activity of biosynthetic pathways for purine and sulfur-containing amino acids. Hydrogen peroxide stress and overproduction of TR collectively resulted in the up-regulation of 267 genes. A total of 16 genes showed a response to both TR overproduction and hydrogen peroxide stress. These genes are involved in the purine metabolism, central metabolism (gapB) as well as in stress-response (groEL, npr2), and transport (mntH2). CONCLUSIONS: Based on our findings we propose that the trxB1-encoded TR in L. plantarum is an important factor in the oxidative stress-associated signal transduction network containing at least 16 genes. This may explain the phenotype of the trxB1-overexpression strain, which appears to be prepared for encountering oxidative stress. This latter property can be used for engineering robustness towards oxidative stress in industrial strains of L. plantarum