Staphylococcus xylosus is a species of bacteria belonging to the genus Staphylococcus. This genus currently includes several species and subspecies. We distinguish between 2 groups: the group of coagulase-positive sta...Staphylococcus xylosus is a species of bacteria belonging to the genus Staphylococcus. This genus currently includes several species and subspecies. We distinguish between 2 groups: the group of coagulase-positive staphylococci (CoPS) and coagulase-negative staphylococci (CoNS), a larger group that includes more than forty species and subspecies. Among the CoNS, Staphylococcus xylosus occupies a special place because it is frequently isolated from meats, dairy products, and agricultural environments. It is commonly used in fermentation due to its primary role in the flavor and color development of fermented products. It is a commensal bacterium of the skin of small mammals and farm animals, where it constitutes the majority of flora. In this species, there are a large number of strains, including phenotypes and genotypes. Although S. xylosus is actually a recognized non-pathogenic species, a few strains can be potentially dangerous. They can thus be responsible for mastitis and dermatitis in cattle. With the multiplicity of breeding farms, the consumption of livestock products and the increasingly frequent contact of humans with animals a few rare cases of human opportunistic infections have also been reported in the literature. These include pyelonephritis, endocarditis, urinary, lymphatic, and lymph node infections, contamination of orthopedic materials and catheters. Thereby, we report the case of a lingering and chronic infection of the lacrimal tract by Staphylococcus xylosus in an 8-year-old child in the Ophthalmology Department of Sikasso hospital in Mali.展开更多
In this paper,the effect of different concentrations of sucrose stress on color formation of the Staphylococcus xylosus was investigated.The results showed that the highest a*value and the best coloring effect similar...In this paper,the effect of different concentrations of sucrose stress on color formation of the Staphylococcus xylosus was investigated.The results showed that the highest a*value and the best coloring effect similar to those of nitrite were observed after the addition of 0.05 g/mL sucrose to stress the S.xylosus.UV-Vis and electron spin resonance spectra analysis showed that production of coloring product Mb-NO was significantly enhanced after 0.05 g/mL sucrose stress.The growth curve,reactive oxygen content,cell cycle,nitric oxide synthase(NOS)activity,zeta potential,cell size,and protein composition of S.xylosus were investigated to reveal the mechanism of sucrose stress to enhance the coloring effect of the strain.The result showed that sucrose inhibited the growth of S.xylosus,which changed the physiological state by activating the oxidative stress response.The stress altered the rate of intracellular metabolism of S.xylosus by delaying the cell cycle and increasing cell surface zeta potential and cell particle size.These changes altered the protein composition of the cells and significantly enhanced the activity of intracellular NOS,which could improve the chromogenic ability of S.xylosus.This study will provide theoretical support for sucrose stress on S.xylosus to enhance its coloring effect,and sucrose stress for S.xylosus might be a promising biological alternative to nitrite in meat products.展开更多
Although coagulase-negative Staphylococcus(CNS),along with technological activities,plays a key role in fermented sausage flavour and nutrient production,the molecular mechanism of these activities remains elusive.In ...Although coagulase-negative Staphylococcus(CNS),along with technological activities,plays a key role in fermented sausage flavour and nutrient production,the molecular mechanism of these activities remains elusive.In this study,18 CNS strains with high proteolytic activity were isolated from Chinese Dong fermented pork(Nanx Wudl),and their technological and transcriptomic properties were investigated.After biochemical identification and genetic analysis,their technological properties,including nitrate reductase,catalase,antioxidant,and lipolytic activities and their growth under varying temperatures,salt concentrations,and p H levels were evaluated.Their aroma-producing potential was also determined in a model medium resembling fermented sausages.Transcriptomic analysis was performed using the most promising isolates.Biochemical identification and 16S rDNA sequencing revealed that the 18 Staphylococcus strains belonged to Staphylococcus xylosus,Staphylococcus saprophyticus,Staphylococcus carnosus,Staphylococcus sciuri,and Staphylococcus equorum.In terms of technological properties,16 strains showed a nitrate-reducing ability,while 11 strains had a lipolytic activity.All strains exhibited superoxide dismutase(SOD)and catalase activities;four strains displayed an SOD activity of>50%.They also tolerated 10%NaCl and 150 mg/kg of nitrite.They showed significant differences in ketone and acid production.The transcriptomic analysis of S.xylosus strains Sx3 and Sx6,which were selected because of their excellent enzymatic activities and aroma-producing ability,revealed the remarkable effect of genes related to pyruvate catabolism and amino acid metabolism on aroma generation.Therefore,this study provided valuable insights into the metabolic mechanisms underlying the technological properties of CNS and identified promising candidates as starter cultures in fermented sausage manufacturing.展开更多
The effect of a proteolytic starter culture isolated from Nanx Wudl,on microbiological,biochemical and organoleptic attributes of dry fermented sausages was investigated during processing.Based on preliminary screenin...The effect of a proteolytic starter culture isolated from Nanx Wudl,on microbiological,biochemical and organoleptic attributes of dry fermented sausages was investigated during processing.Based on preliminary screening,the combination of Staphylococcus xylosus SX16 and Lactobacillus plantarum CMRC6,showing excellent proteolytic activity in vitro,was selected as the multi-strain starter(starter LS).For comparison,the single-strain starter culture of L.plantarum CMRC6(starter LB)and non-inoculated control were also tested.During fermentation,lactic acid bacteria and staphylococci dominated the microbiota and suppressed the Enterobacteriaceae growth in LS-inoculated sausages.The addition of LS starter accelerated acidification and proteolysis during ripening,improving the contents of total free amino acids and several essential free amino acids(Phe,Ile and Leu).Volatile compounds analysis revealed that LS-fermented sausage showed the highest abundance of 3-methyl-1-butanol,probably due to the inoculated S.xylosus.The inoculation of LS starter improved the sensory properties of sausages,especially the flavor attribute.Therefore,S.xylosus SX16 and L.plantarum CMRC6 are promising candidates for inclusion as multi-strain starters in the manufacture of gourmet fermented dry sausage.展开更多
文摘Staphylococcus xylosus is a species of bacteria belonging to the genus Staphylococcus. This genus currently includes several species and subspecies. We distinguish between 2 groups: the group of coagulase-positive staphylococci (CoPS) and coagulase-negative staphylococci (CoNS), a larger group that includes more than forty species and subspecies. Among the CoNS, Staphylococcus xylosus occupies a special place because it is frequently isolated from meats, dairy products, and agricultural environments. It is commonly used in fermentation due to its primary role in the flavor and color development of fermented products. It is a commensal bacterium of the skin of small mammals and farm animals, where it constitutes the majority of flora. In this species, there are a large number of strains, including phenotypes and genotypes. Although S. xylosus is actually a recognized non-pathogenic species, a few strains can be potentially dangerous. They can thus be responsible for mastitis and dermatitis in cattle. With the multiplicity of breeding farms, the consumption of livestock products and the increasingly frequent contact of humans with animals a few rare cases of human opportunistic infections have also been reported in the literature. These include pyelonephritis, endocarditis, urinary, lymphatic, and lymph node infections, contamination of orthopedic materials and catheters. Thereby, we report the case of a lingering and chronic infection of the lacrimal tract by Staphylococcus xylosus in an 8-year-old child in the Ophthalmology Department of Sikasso hospital in Mali.
基金the National Natural Science Foundation of China(No.31501512)。
文摘In this paper,the effect of different concentrations of sucrose stress on color formation of the Staphylococcus xylosus was investigated.The results showed that the highest a*value and the best coloring effect similar to those of nitrite were observed after the addition of 0.05 g/mL sucrose to stress the S.xylosus.UV-Vis and electron spin resonance spectra analysis showed that production of coloring product Mb-NO was significantly enhanced after 0.05 g/mL sucrose stress.The growth curve,reactive oxygen content,cell cycle,nitric oxide synthase(NOS)activity,zeta potential,cell size,and protein composition of S.xylosus were investigated to reveal the mechanism of sucrose stress to enhance the coloring effect of the strain.The result showed that sucrose inhibited the growth of S.xylosus,which changed the physiological state by activating the oxidative stress response.The stress altered the rate of intracellular metabolism of S.xylosus by delaying the cell cycle and increasing cell surface zeta potential and cell particle size.These changes altered the protein composition of the cells and significantly enhanced the activity of intracellular NOS,which could improve the chromogenic ability of S.xylosus.This study will provide theoretical support for sucrose stress on S.xylosus to enhance its coloring effect,and sucrose stress for S.xylosus might be a promising biological alternative to nitrite in meat products.
基金the financial support of the National Natural Science Foundation of China(32102016)the Taishan Industrial Experts Program。
文摘Although coagulase-negative Staphylococcus(CNS),along with technological activities,plays a key role in fermented sausage flavour and nutrient production,the molecular mechanism of these activities remains elusive.In this study,18 CNS strains with high proteolytic activity were isolated from Chinese Dong fermented pork(Nanx Wudl),and their technological and transcriptomic properties were investigated.After biochemical identification and genetic analysis,their technological properties,including nitrate reductase,catalase,antioxidant,and lipolytic activities and their growth under varying temperatures,salt concentrations,and p H levels were evaluated.Their aroma-producing potential was also determined in a model medium resembling fermented sausages.Transcriptomic analysis was performed using the most promising isolates.Biochemical identification and 16S rDNA sequencing revealed that the 18 Staphylococcus strains belonged to Staphylococcus xylosus,Staphylococcus saprophyticus,Staphylococcus carnosus,Staphylococcus sciuri,and Staphylococcus equorum.In terms of technological properties,16 strains showed a nitrate-reducing ability,while 11 strains had a lipolytic activity.All strains exhibited superoxide dismutase(SOD)and catalase activities;four strains displayed an SOD activity of>50%.They also tolerated 10%NaCl and 150 mg/kg of nitrite.They showed significant differences in ketone and acid production.The transcriptomic analysis of S.xylosus strains Sx3 and Sx6,which were selected because of their excellent enzymatic activities and aroma-producing ability,revealed the remarkable effect of genes related to pyruvate catabolism and amino acid metabolism on aroma generation.Therefore,this study provided valuable insights into the metabolic mechanisms underlying the technological properties of CNS and identified promising candidates as starter cultures in fermented sausage manufacturing.
基金the National Key R&D Program of China(grant no.2018YFD0400404).
文摘The effect of a proteolytic starter culture isolated from Nanx Wudl,on microbiological,biochemical and organoleptic attributes of dry fermented sausages was investigated during processing.Based on preliminary screening,the combination of Staphylococcus xylosus SX16 and Lactobacillus plantarum CMRC6,showing excellent proteolytic activity in vitro,was selected as the multi-strain starter(starter LS).For comparison,the single-strain starter culture of L.plantarum CMRC6(starter LB)and non-inoculated control were also tested.During fermentation,lactic acid bacteria and staphylococci dominated the microbiota and suppressed the Enterobacteriaceae growth in LS-inoculated sausages.The addition of LS starter accelerated acidification and proteolysis during ripening,improving the contents of total free amino acids and several essential free amino acids(Phe,Ile and Leu).Volatile compounds analysis revealed that LS-fermented sausage showed the highest abundance of 3-methyl-1-butanol,probably due to the inoculated S.xylosus.The inoculation of LS starter improved the sensory properties of sausages,especially the flavor attribute.Therefore,S.xylosus SX16 and L.plantarum CMRC6 are promising candidates for inclusion as multi-strain starters in the manufacture of gourmet fermented dry sausage.
