Several [Fe-S] clusters containing enzymes (pyruvate-ferredoxin-oxidoreductase, ferredoxin, hydrogenase) participate in the production of acetyl-CoA from pyruvate in clostridia while lactate production

by LDH does not require [Fe-S] clusters [53, 54]. The conversion of pyruvate to acetyl-CoA is therefore dependent on the iron and cysteine supply. C. perfringens might increase LDH synthesis during cysteine limitation to decrease the excess of reducing equivalents produced by glycolysis combined with low [Fe-S] cluster requirements. Interestingly, the lactate production is increased during iron starvation in C. acetobutylicum [55]. Regulation of genes involved in redox systems Genes involved in see more electron transfer and maintenance of the cell redox status were also differentially expressed in response to cysteine availability. The expression of cpe2511 encoding a [3Fe-4S] ferredoxin was up-regulated in the presence of homocysteine while that of cpe2447 encoding a 2[2Fe-2S] ferredoxin playing a role in shuttling electrons between a number of redox enzymes [53] increased in the presence of cystine. The rubR1 and rubR2 genes SB525334 encode rubredoxins. These proteins contain an iron associated to 4 cysteinyl residues and play a role in electron transfers for the nitrate reductase or the NADH/rubredoxin oxidoreductase involved in

oxygen and reactive oxygen species detoxification [56, 57]. The rubR genes were about 2-fold Dolutegravir concentration more expressed in the presence of homocysteine than in the presence of cystine. We confirmed by qRT-PCR that rubR2 was 4-fold up-regulated during cysteine limitation. The rubredoxins participate in the oxidative stress response in C. perfringens and C. acetobutylicum [56, 58] via their role in electron transfer for the NADH/rubredoxin oxidoreductase involved in the detoxification of oxygen and reactive oxygen species

[59, 60]. We then tested the sensitivity of strain 13 to stresses after growth in the presence of homocysteine or cystine. The growth inhibition area in the presence of H2O2 and diamide increased 11 and 13% (p-value <0.05), respectively in the presence of homocysteine as compared with cystine while no difference was observed with paraquat. So, the strain 13 appeared more sensitive to H2O2 and diamide during cysteine depletion despite the induction of rubR1 and rubR2 transcription. This induction is probably not sufficient to increase the resistance to H2O2 in the absence of induction of other scavenging components [NADH/rubredoxin oxidoreductase, FprA, Rubperoxin (formerly reverse rubrerythrin)]. The increased sensitivity of strain 13 to H2O2 and disulfide stress may be rather due to cysteine depletion during growth with homocysteine. Cysteine is a precursor of glutathione that is detected in C perfringens [61]. Glutathione plays a key role in thiol homeostasis and in protein protection after an oxidative stress [62]. However, genes involved in glutathione biosynthesis (Fig.