Cystine uptake prevents production of hydrogen peroxide byLactobacillus fermentumBR11

Abstract

BspA is an abundant surface protein from Lactobacillus fermentum BR11, and is required for normal cystine uptake. In previous studies, a mutant strain deficient in BspA (L. fermentum PNG201) was found to be sensitive to oxidative stress. In this study, the biochemical basis for this was explored. It was found that under aerobic batch culture conditions in de Mann^Rogosa^Sharpe medium, both L. fermentum BR11 and PNG201 entered stationary phase due to hydrogen peroxide accumulation. However, this took place at a lower optical density for PNG201 than for BR11. Measurements of hydrogen peroxide levels revealed that the BspA mutant strain overproduces this compound. Addition of 6 mM cystine to aerobic cultures was found to prevent hydrogen peroxide production by both the BR11 and PNG201 strains, but lower cystine concentrations depressed hydrogen peroxide production in BR11 more efficiently than in PNG201. Each mole of cystine was able to prevent the production of several moles of hydrogen peroxide by L. fermentum BR11, suggesting that hydrogen peroxide breakdown is dependent upon a thiol that cycles between reduced and oxidized states. It was concluded that peroxide breakdown by L. fermentum BR11 is dependent upon exogenous cystine. It is most probable that the imported L-cystine is catabolized by a cystathionine lyase and then converted into a thiol reductant for a peroxidase.

The l-Cysteine/l-Cystine Shuttle System Provides Reducing Equivalents to the Periplasm in Escherichia coli

“…3, A and B). The latter finding is consistent with the previous observation in L. fermentum (30). It should be noted that, as FliY is a periplasmic solute-binding protein, FliY probably cooperates with a certain transporter for the uptake of L-cystine (Fig.…”

Effects of a Lactobacillus reuteri BR11 Mutant Deficient in the Cystine-Transport System in a Rat Model of Inflammatory Bowel Disease

“…The uptake system of L. reuteri BR11 comprises a high affinity cystine binding protein termed Cystine Uptake C (CyuC), a component of the ATP binding cassette cystine transport system [20]. In order to determine the role of this unique system, the cyuC gene was inactivated using homologous recombination to produce a L. reuteri mutant (PNG201) deficient in cystine uptake [13,21]. Utilizing a rat model of colitis induced by ingesting dextran sulfate sodium (DSS) it was hypothesized that elimination of the CyuC protein, which effectively inactivates the entire transport of cystine, would result in a decreased ability of the bacteria to prevent colonic injury.…”

Cystathionine γ-Lyase Is a Component of Cystine-Mediated Oxidative Defense in Lactobacillus reuteri BR11

“…L. reuteri rapidly transports cystine and converts it to a thiol(s), which is, at least in part, secreted from the cell in a process requiring CyuC (47). A cyuC-deficient mutant was found to be more sensitive to oxidative stress due to overproduction of hydrogen peroxide in the presence of oxygen (18). It was therefore concluded that the CyuC transporter plays a role in oxidative defense of L. reuteri BR11 by deriving thiols from exogenous cystine.…”

“…In addition, sulfur amino acid lyases are unique in that they are able to produce free thiols without consuming reducing equivalents (47). Therefore, it is reasonable to hypothesize that Cgl works in concert with the CyuC transporter in oxidative defense by cleaving cystine into thiols that act as reductants for thiol peroxidases (18,47). Alternatively, thiols may reduce hydrogen peroxide nonenzymatically, as shown in the spontaneous reaction between sulfides and hydrogen peroxide (42).…”