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:RNA-seq was used in combination with various analytical chemistry approaches to identify the chemical and genetic basis of pigment production of the bacterium Glutamicibacter arilaitensis when growing on cheese. This bacterium commonly found in cheese rinds where it co-occurs with Penicillium species and other molds. Pinkish-red pigments are produced by the bacterium in response to growth with Penicillium. Both chemical analyses and RNA-seq point to coproporphyrin III as the major metabolite leading to pigment formation.
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:The viability and competitiveness of Staphylococcus xylosus in meat mostly depend on the ability to adapt itself to rapid oxygen and nutrients depletion during meat fermentation. The utilization of nitrite instead of oxygen becomes a successful strategy for this strain to improve its performance in anaerobiosis; however, metabolic pathways of this strain underlying this adaptation, are partially known. The aim of this study was to provide an overview on proteomic changes of S. xylosus DSM 20266T cultured under anaerobiosis and nitrite exposure. Thus, two different cultures of this strain, supplemented or not with nitrite, were in vitro incubated in aerobiosis and anaerobiosis monitoring cell viability, pH, oxidation reduction potential and nitrite content. Protein extracts, obtained from cells, collected as nitrite content was depleted, were analyzed by 2DE/MALDI-TOF/TOF-MS. Results showed that DSM 20266T growth was significantly sustained by nitrite in anaerobiosis, whereas no differences were found in aerobiosis. Accordingly, nitrite content was depleted after 13 h only in anaerobiosis. At this time of sampling, a comparative proteomic analysis showed 45 differentially expressed proteins. Most differences were found between aerobic and anaerobic cultures without nitrite; the induction of glycolytic enzymes and glyoxylate cycle, the reduction of TCA enzymes, and acetate fermentation were found in anaerobiosis to produce ATP and maintain the cell redox balance. In anaerobic cultures the nitrite supplementation partially restored TCA cycle, and reduced the amount of glycolytic enzymes. These results were confirmed by phenotypic microarray that, for the first time, was carried out on cell previously adapted at the different growth conditions. Overall, metabolic changes were similar between aerobiosis and anaerobiosis NO2-adapted cells, whilst cells grown under anaerobiosis showed different assimilation profiles by confirming proteomic data; indeed, these latter extensively assimilated substrates addressed at both supplying glucose for glycolysis or fueling alternative pathways to TCA cycle. In conclusion, metabolic pathways underlying the ability of S. xylosus to adapt itself to oxygen starvation were revealed; the addition of nitrite allowed S. xylosus to take advantage of nitrite to this condition, restoring some metabolic pathway underlying aerobic behavior of the strain.