Project description:Staphylococcus xylosus is one of the major starter cultures used for meat fermentation because of its crucial role in the reduction of nitrate to nitrite, which contributes to color and flavor development. Despite the long use of these additives, their impact on the physiology of S. xylosus has not yet been explored. We present the first in situ global gene expression profile of S. xylosus in meat supplemented with nitrate and nitrite. More than 600 genes of S. xylosus were differentially expressed at 24 or 72 hours of incubation. They represent more than 20% of the total genes and led us to suppose that addition of nitrate and nitrite to meat leads to a global change in gene expression. This profile revealed that S. xylosus is subject to nitrosative stress caused by reactive nitrogen species generated from nitrate and nitrite. To overcome this stress, S. xylosus has developed several oxidative stress resistance mechanisms, such as modulation of the expression of several genes involved in iron homeostasis and in antioxidant defense. Most of these genes belong to the Fur and PerR regulons respectively. S. xylosus has also counteracted this stress by developing DNA and protein repair. Furthermore, it has adapted its metabolic responseM-bM-^@M-^Tcarbon and nitrogen metabolism, energy production and cell wall biogenesisM-bM-^@M-^Tto the alterations produced by nitrosative stress. Microarray was used to evaluate modification in the transcriptome of S. xylosus C2a strain in the presence (N) or absence (V) of nitroso compounds. Three biological replicates collected on separate days for each meat matrix and labelled following a dye-switch design; for each condition one labeling in Cy3 and one in Cy5.
Project description:Staphylococcus xylosus is one of the major starter cultures used for meat fermentation because of its crucial role in the reduction of nitrate to nitrite, which contributes to color and flavor development. Despite the long use of these additives, their impact on the physiology of S. xylosus has not yet been explored. We present the first in situ global gene expression profile of S. xylosus in meat supplemented with nitrate and nitrite. More than 600 genes of S. xylosus were differentially expressed at 24 or 72 hours of incubation. They represent more than 20% of the total genes and led us to suppose that addition of nitrate and nitrite to meat leads to a global change in gene expression. This profile revealed that S. xylosus is subject to nitrosative stress caused by reactive nitrogen species generated from nitrate and nitrite. To overcome this stress, S. xylosus has developed several oxidative stress resistance mechanisms, such as modulation of the expression of several genes involved in iron homeostasis and in antioxidant defense. Most of these genes belong to the Fur and PerR regulons respectively. S. xylosus has also counteracted this stress by developing DNA and protein repair. Furthermore, it has adapted its metabolic response—carbon and nitrogen metabolism, energy production and cell wall biogenesis—to the alterations produced by nitrosative stress.
Project description:Staphylococcus xylosus is used as starter culture for sausage fermentation for a long time but the molecular mechanisms for its adaptation in meat remained unknown. A global transcriptomic approach was carried out to determine these molecular mechanisms. S. xylosus modulated the expression of about 30% of the total genes during its growth and survival in the meat model. The expression of many genes encoding enzymes involved in glucose and lactate catabolism was up regulated. In parallel, genes encoding transport of peptides and peptidases that could furnish amino acids were up expressed and thus concomitantly a lot of genes involved in amino acids synthesis were down regulated. Finally S. xylosus responded to salt added in the meat model by over expressing genes involved in transport and synthesis of osmoprotectants, Na+ and H+ extrusion and in production of energy through the F0F1-ATPase.
Project description:Staphylococcus xylosus is used as starter culture for sausage fermentation for a long time but the molecular mechanisms for its adaptation in meat remained unknown. A global transcriptomic approach was carried out to determine these molecular mechanisms. S. xylosus modulated the expression of about 30% of the total genes during its growth and survival in the meat model. The expression of many genes encoding enzymes involved in glucose and lactate catabolism was up regulated. In parallel, genes encoding transport of peptides and peptidases that could furnish amino acids were up expressed and thus concomitantly a lot of genes involved in amino acids synthesis were down regulated. Finally S. xylosus responded to salt added in the meat model by over expressing genes involved in transport and synthesis of osmoprotectants, Na+ and H+ extrusion and in production of energy through the F0F1-ATPase. Microarray was used to evaluate modification in the transcriptome of S. xylosus C2a strain in the inoculum (Mx) or in meat (V). Three biological replicates were collected on separate days for samples and labelled following a dye-switch design; for each condition one labeling in Cy3 and one in Cy5.
Project description:Acididesulfobacillus acetoxydans is an acidophilic sulfate reducer that can dissimilatory reduce nitrate to ammonia (DNRA). However, no known nitrite reductase is encoded. This study was performed to investigate how A. acetoxydans reduces nitrate to nitrite and elucidated a novel DNRA mechanism and potential nitrosative stress resistance mechanisms in acidophiles.
Project description:Aims: Coagulase negative Staphylococcus xylosus strains are used as starter organisms for sausage fermentation. As those strains have to cope with low pH-values during fermentation, the aim of this study was to identify the acid adaptation mechanisms of S. xylosus TMW 2.1523 previously isolated from salami. Methods and Results: A comparative proteomic study between two different acid tolerant mutants was performed. Therefore, both S. xylosus mutants were grown pH-static under acid stress (pH 5.1) and reference conditions (pH 7.0). Proteomic data were supported by metabolite and cell membrane lipids analyses. S. xylosus acid stress adaptation is mainly characterized by a metabolic change towards neutral metabolites, enhanced urease activity, reduced ATP consumption, an increase in membrane fluidity and changes of the membrane thickness. Conclusion: This study corroborates mechanisms as previously described for other Gram-positive bacteria. Additionally, the adjustment of membrane structure and composition in S. xylosus TMW 2.1523 play a prominent role in its acid adaptation. Significance and Impact of the Study: This study demonstrates for the first time changes of the membrane lipid composition due to acid stress adaptation in staphylococci.