As a specific spoilage organism of seafood under refrigerated temperature conditions,Shewanella spp.tend to form biofilms that exacerbate the occurrence of seafood spoilage.Biofilm-promoting factor A(BpfA)has been rep...As a specific spoilage organism of seafood under refrigerated temperature conditions,Shewanella spp.tend to form biofilms that exacerbate the occurrence of seafood spoilage.Biofilm-promoting factor A(BpfA)has been reported to promote the adhesion and biofilm formation of Shewanella spp.,but its role in adhesion and biofilm formation of S.putrefaciens under cold stress needs to be further investigated.To better comprehend the effect of BpfA on adhesion and biofilm formation of S.putrefaciens under cold stress(4℃),bacterial adhesion and biofilm phenotype of S.putrefaciens CN32 WT andΔbpfA at 4℃were analyzed and performed transcriptomics.The results showed that the deletion of bpfA had almost no effect on the growth of S.putrefaciens CN32 at 4℃,but weakened the unicellular adhesion capacity of S.putrefaciens CN32 and destabilized the stability of the multicellular adhesion layer.In addition,the biomass of the mature biofilm formed byΔbpfA was merely around 50%of that observed in the mature biofilm of S.putrefaciens CN32 WT,the average thickness and volume of the biofilm decreased by 18%and 27%,respectively,and the composition of the biofilm changed.Transcriptome analysis demonstrated that the deletion of bpfA led to differential expression of genes involved in metabolic pathways such as bacterial chemotaxis,two-component system,tyrosine metabolism,drug metabolism-other enzymes and biofilm formation-Vibrio cholerae,which in turn influenced bacterial adhesion and biofilm formation.Those results advance our acknowledgment of the character of BpfA on adhesion and biofilm formation of S.putrefaciens CN32,which contributes to understanding bacterial adhesion and the control of biofilm formation.展开更多
In Northwest Florida, the soil is mainly covered by poorly drained sandy soil of Myakka, which is characterized by a subsurface accumulation of humus and AI and Fe oxides. When organic rich landfill leachate is leaked...In Northwest Florida, the soil is mainly covered by poorly drained sandy soil of Myakka, which is characterized by a subsurface accumulation of humus and AI and Fe oxides. When organic rich landfill leachate is leaked to the iron rich soils, ferrous iron is released with the oxidation of organic compounds in the leachate. In this research, we investigated the activities of S. putrefaciens in reducing iron oxide in the iron rich soil of Northwest Florida with landfill leachate serving as the carbon source. S. putrefaciens had similar maximum specific growth rate and half saturation coefficients for all the leachate and soil samples. The average maximum specific growth rate was 0.008 hr^-1 and the average half saturation coefficient was 243.8 mg/L. Averagely, 2.2 mg ferrous iron was generated per mg COD consumed. In addition, adsorption of reduced ferrous iron on S. putrefaciens was further characterized. Ferrous iron adsorption on S. putrefaciens was a kinetic process, which increased with the increase of the reaction time. Equilibrium ferrous iron adsorption on S. putrefaciens can be reached after three hours. Ferrous iron had linear adsorption isotherms on S. putrefaciens for the pH range of 5 to 9.展开更多
In this study, Pb(Ⅱ) was used as a target heavy metal pollutant, and the metabolism of Shewanella putrefaciens(S. putrefaciens) was applied to achieve reducing conditions to study the effect of microbial reduction on...In this study, Pb(Ⅱ) was used as a target heavy metal pollutant, and the metabolism of Shewanella putrefaciens(S. putrefaciens) was applied to achieve reducing conditions to study the effect of microbial reduction on lead that was preadsorbed on graphene oxide(GO) surfaces.The results showed that GO was transformed to its reduced form(r-GO) by bacteria, and this process induced the release of Pb(Ⅱ) adsorbed on the GO surfaces. After 72 hr of exposure in an S. putrefaciens system, 5.76% of the total adsorbed Pb(Ⅱ) was stably dispersed in solution in the form of a Pb(Ⅱ)-extracellular polymer substance(EPS) complex, while another portion of Pb(Ⅱ) released from GO-Pb(Ⅱ) was observed as lead phosphate hydroxide(Pb_(10)(PO_(4))_(6)(OH)_(2))precipitates or adsorbed species on the surface of the cell. Additionally, increasing pH induced the stripping of oxidative debris(OD) and elevated the content of dispersible Pb(Ⅱ)in aqueous solution under the conditions of S. putrefaciens metabolism. These research results provide valuable information regarding the migration of heavy metals adsorbed on GO under reducing conditions due to microbial metabolism.展开更多
Shewanella putrefaciens(S.putrefaciens)is a key spoilage bacterium in aquatic products and exhibits a strong tendency to rot.Carnosic acid(CA)has attracted widespread attention as a natural antibacterial agent.In this...Shewanella putrefaciens(S.putrefaciens)is a key spoilage bacterium in aquatic products and exhibits a strong tendency to rot.Carnosic acid(CA)has attracted widespread attention as a natural antibacterial agent.In this study,we evaluated the antibacterial activity and mechanism of action of the natural antimicrobial agent CA against S.putrefaciens at the metabolic molecule level.The effect of CA on S.putrefaciens at the metabolic molecules level was analysed by using metabolomics.CA exhibited inhibited bacterial proliferation at a concentration of 0.2 mg/mL and completely killed bacteria at 0.4 mg/mL.Morphological analysis revealed fragmented cells with increased membrane permeability.This was accompanied by decreased respiratory metabolic viability and metabolic enzyme activity,suggesting that CA inhibited cellular respiration and energy synthesis of S.putrefaciens.Metabolomic analysis indicated that CA interfered with nucleotide metabolism,tricarboxylic acid cycle,biosynthesis of pantothenate and coenzyme A,and amino acid metabolism,and affected energy cycle,cell membrane structure,and expression of genetic material,which led to growth inhibition and bacterial death.These results indicate that CA exerts antibacterial effects by damaging the cell membrane,altering bacterial metabolism,and impairing oxidative respiration.We provide a theoretical basis for controlling S.putrefaciens and offer insights for improving the safety and shelf life of aquatic products.展开更多
Shewanella putrefaciens and Listeria monocytogenes are concerned by scientists and consumers due to their ability to produce dense biofilms to contaminate and cause food spoilage.The object of this study was to invest...Shewanella putrefaciens and Listeria monocytogenes are concerned by scientists and consumers due to their ability to produce dense biofilms to contaminate and cause food spoilage.The object of this study was to investigate the antimicrobial and anti-biofilm activities of octyl gallate(OG)against the two food-related bacteria.Results showed that the antimicrobial activities of OG were in a dose-dependent manner and the minimum inhibitory concentration(MIC)of S.putrefaciens and L.monocytogenes were 0.2 mmol/L and 0.1 mmol/L,respectively.OG can rapidly penetrate the bacteria and produce reactive oxygen species(ROS).Then,OG and ROS can lead to membrane damage and cell rupture,causing DNA and protein leakage.Our data also strongly suggested that OG not only can inhibit biofilms formation,but also eradicate the performed biofilms.Furthermore,it was shown that OG,as an additive,has great potential in antimicrobial application to prolong the shelf life of large yellow croakers.These prove that OG can combat bacteria and eradicate biofilm against S.putrefaciens and L.monocytogenes.展开更多
This study investigated the antibacterial action of cinnamon essential oil(CEO)on Shewanella putrefaciens using untargeted metabolomics for the first time.The results demonstrated that CEO effectively suppressed the g...This study investigated the antibacterial action of cinnamon essential oil(CEO)on Shewanella putrefaciens using untargeted metabolomics for the first time.The results demonstrated that CEO effectively suppressed the growth of S.putrefaciens with a minimal inhibition concentration(MIC)of 0.078μL/mL.CEO induced significant morphological and ultrastructural distortions in S.putrefaciens as well as serious damage to both the outer and inner membranes.Following exposure to CEO at 1×MIC,cell membrane permeability of S.putrefaciens increased significantly,as evidenced by a 5.10-fold rise in propidium iodide fluorescence intensity and a 0.39-fold increase in 1-N-phenylnaphthylamine fluorescence intensity compared to the control,along with membrane depolarization.These changes resulted in the leakage of crucial biological macromolecules,such as nucleic acids and proteins.Additionally,CEO at 1×MIC triggered the accumulation of reactive oxygen species by an 85.71%increase in 2′,7′-dichlorofluorescein diacetate fluorescence intensity within S.putrefaciens cells relative to the control,suggesting oxidative damage.Untargeted metabolomic analysis revealed that CEO at 1/2×MIC altered the metabolic profile,affecting several metabolic pathways,mainly including amino acid metabolism,nucleotide metabolism,glutathione metabolism,the one-carbon pool by folate,pantothenate and coenzyme A biosynthesis,and glycerophospholipid metabolism.These alterations could potentially disrupt nucleic acid metabolism,energy metabolism,and membrane stability,while activating the nucleotide salvage synthesis,sustaining redox homeostasis,and enhancing the overall adaptive capacity of S.putrefaciens.This study enhances the understanding of the antibacterial action of CEO and underscores its potential as a natural food preservative.展开更多
The antimicrobial mechanism of Ginkgo biloba leaf extracts(GBLE)when applied to predominant spoilage bacteria(Shewanella putrefaciens and Saprophytic staphylococcus)on refrigerated pomfret and minimal inhibitory conce...The antimicrobial mechanism of Ginkgo biloba leaf extracts(GBLE)when applied to predominant spoilage bacteria(Shewanella putrefaciens and Saprophytic staphylococcus)on refrigerated pomfret and minimal inhibitory concentrations(MICs)were measured by the plate counting method.GBLE at MIC and 2MIC were prepared in tryptic soy broth(TSB)medium and equivalent amounts of sterile distilled water were used in place of GBLE as a control group.The impact of GBLE on the growth of bacteria,the permeability of cell membrane,and cell wall were also investigated by growth curve of bacteria,alkaline phosphates activity(AKP),and electrical conductivity.A scanning electron microscope(SEM)was used to study the effects of GBLE on the cellular structure of S.putrefaciens and S.staphylococcus.The results showed that the MICs of GBLE when applied to S.putrefaciens and S.staphylococcus were 100 mg/mL,the inhibitory rates of MIC and 2MIC concentrations of GBLE when applied to S.putrefaciens were 36.11%and 100%,while 27.78%and 62.22%for S.staphylococcus.Meanwhile,GBLE inhibited the growth of S.putrefaciens and S.staphylococcus until the number of cells at 2MIC values decreased to 0 and 4.29 log CFU/mL,respectively,after 24 h.The electrical conductivity of bacteria increased with GBLE treatment,which was followed by an increased leakage of AKP.The SEM revealed that the structure of bacterial cells was destroyed and the bacteria began to be adhere to each other.The inhibition effect of GBLE when applied to S.putrefaciens and S.staphylococcus was related to the damage of cell membrane and cell wall.It was also revealed that GBLE damages the morphology of bacteria and had stronger effects on the cell membrane of S.putrefaciens than that of S.staphylococcus.展开更多
Shewanella putrefaciens is one of the common spoilage microorganisms in aquatic products,and its extracellular protease is the main cause of seafood spoilage.The characteristics of the extracellular protease produced ...Shewanella putrefaciens is one of the common spoilage microorganisms in aquatic products,and its extracellular protease is the main cause of seafood spoilage.The characteristics of the extracellular protease produced by S.putrefaciens YZ08 and its hydrolytic properties on fish proteins were studied.After purification,an extracellular protease of 18.78 kDa was obtained and identified as a metalloprotease of the M23 family.The gene encoding this enzyme was cloned and purified by expression in E.coli to obtain a recombinant protease.YZ08 protease showed optimum enzymatic activity at 40℃ and pH 9.0 and was stable at pH 7.0-10.0 and low temperature(<40℃).The kinetic parameters and thermal inactivation parameters of the enzyme were determined.S.putrefaciens YZ08 protease can degrade fish myofibrillar and sarcoplasmic proteins,breaking them down into small particles and low molecular peptides.The three-dimensional structure of the protease was simulated by homology modeling and revealed a correlation between the active site in the protein and substrate specificity.This work provides a foundation for characterizing the properties of S.putrefaciens YZ08 protease and for controlling the quality and safety of seafood.展开更多
Objectives:The bacteriostatic effects of a citral nanoemulsion against Shewanella putrefaciens CN-32(SHP CN-32)were investigated using in vitro culture and gene expression analysis,forbuilding a potential application ...Objectives:The bacteriostatic effects of a citral nanoemulsion against Shewanella putrefaciens CN-32(SHP CN-32)were investigated using in vitro culture and gene expression analysis,forbuilding a potential application in spoilage microorganism control and aquatic products quality maintenance.Materials and Methods:SHP CN-32 was treated by prepared citral nanoemulsion when the minimal inhibitory concentration(MIC)was verified.The growth curve,membrane integrity,scanning electron microscope(SEM)observation,biofilm formation and quorum sensing(QS)signaling molecule Al-2 content were evaluated in different MIC treatment groups(0 to 1.00 MIC).The gene expression status of SHP CN-32 in O and 0.50 MIC groups were compared using transcriptome sequencing and quantitative polymerase chain reaction(PCR).Results:The in vitro culture revealed that the citral nanoemulsion could inhibit the growth of SHP CN-32 with MIC of approximately 200μg/mL.Images of membrane integrity.SEM and biofilm formation suggested significant biological structure damage in bacteria after treatment.Meanwhile,the Qs signaling molecule Al-2 content showed a decline with increasing treatment concentration.Transcriptome sequencing and quantitative PCR revealed that the majority genes related diversified functional metabolic pathways of SHP CN-32 were downregulated at varying degree.Conclusion:A significant bacteriostasis of citral nanoemulsion against SHP CN-32 was verified via the results of growth inhibition,structural destruction,signal molecular decrease and gene expression downregulation of strains.These synergies significantly affect the characteristic expression of SHP CN-32,revealing the application potential as bacteriostat,QS inhibitor and preservative in aquatic products.展开更多
We report a case of skin and soft tissue infection, peritonitis and bacteriemia in a 51-year-old drug abuse male. His wife found him lifeless lying on the kitchen floor at his residence. At the time of autopsy, multip...We report a case of skin and soft tissue infection, peritonitis and bacteriemia in a 51-year-old drug abuse male. His wife found him lifeless lying on the kitchen floor at his residence. At the time of autopsy, multiple skin ulcers with deep soft tissue infection and peritonitis were found on gross examination. Cultures of postmortem blood and a swab of soft tissue were positive for Shewanella putrefaciens, a gram-negative bacterium that had been isolated from many foods, sewage and fresh and salt water. This is the first reported case in the United States of fatal skin and soft tissue infection, peritonitis and bacteremia caused by this micro-organism.展开更多
基金funded by the National Natural Science Foundation of China(32472401).
文摘As a specific spoilage organism of seafood under refrigerated temperature conditions,Shewanella spp.tend to form biofilms that exacerbate the occurrence of seafood spoilage.Biofilm-promoting factor A(BpfA)has been reported to promote the adhesion and biofilm formation of Shewanella spp.,but its role in adhesion and biofilm formation of S.putrefaciens under cold stress needs to be further investigated.To better comprehend the effect of BpfA on adhesion and biofilm formation of S.putrefaciens under cold stress(4℃),bacterial adhesion and biofilm phenotype of S.putrefaciens CN32 WT andΔbpfA at 4℃were analyzed and performed transcriptomics.The results showed that the deletion of bpfA had almost no effect on the growth of S.putrefaciens CN32 at 4℃,but weakened the unicellular adhesion capacity of S.putrefaciens CN32 and destabilized the stability of the multicellular adhesion layer.In addition,the biomass of the mature biofilm formed byΔbpfA was merely around 50%of that observed in the mature biofilm of S.putrefaciens CN32 WT,the average thickness and volume of the biofilm decreased by 18%and 27%,respectively,and the composition of the biofilm changed.Transcriptome analysis demonstrated that the deletion of bpfA led to differential expression of genes involved in metabolic pathways such as bacterial chemotaxis,two-component system,tyrosine metabolism,drug metabolism-other enzymes and biofilm formation-Vibrio cholerae,which in turn influenced bacterial adhesion and biofilm formation.Those results advance our acknowledgment of the character of BpfA on adhesion and biofilm formation of S.putrefaciens CN32,which contributes to understanding bacterial adhesion and the control of biofilm formation.
文摘In Northwest Florida, the soil is mainly covered by poorly drained sandy soil of Myakka, which is characterized by a subsurface accumulation of humus and AI and Fe oxides. When organic rich landfill leachate is leaked to the iron rich soils, ferrous iron is released with the oxidation of organic compounds in the leachate. In this research, we investigated the activities of S. putrefaciens in reducing iron oxide in the iron rich soil of Northwest Florida with landfill leachate serving as the carbon source. S. putrefaciens had similar maximum specific growth rate and half saturation coefficients for all the leachate and soil samples. The average maximum specific growth rate was 0.008 hr^-1 and the average half saturation coefficient was 243.8 mg/L. Averagely, 2.2 mg ferrous iron was generated per mg COD consumed. In addition, adsorption of reduced ferrous iron on S. putrefaciens was further characterized. Ferrous iron adsorption on S. putrefaciens was a kinetic process, which increased with the increase of the reaction time. Equilibrium ferrous iron adsorption on S. putrefaciens can be reached after three hours. Ferrous iron had linear adsorption isotherms on S. putrefaciens for the pH range of 5 to 9.
基金supported by the National Key Project of Research and Development Plan of China (No. 2017YFC04034033)the Shanxi National Science Foundation (No. 2020JQ-664)the Key Laboratory of Education Department of Shanxi Province, China (No. 20JS085)。
文摘In this study, Pb(Ⅱ) was used as a target heavy metal pollutant, and the metabolism of Shewanella putrefaciens(S. putrefaciens) was applied to achieve reducing conditions to study the effect of microbial reduction on lead that was preadsorbed on graphene oxide(GO) surfaces.The results showed that GO was transformed to its reduced form(r-GO) by bacteria, and this process induced the release of Pb(Ⅱ) adsorbed on the GO surfaces. After 72 hr of exposure in an S. putrefaciens system, 5.76% of the total adsorbed Pb(Ⅱ) was stably dispersed in solution in the form of a Pb(Ⅱ)-extracellular polymer substance(EPS) complex, while another portion of Pb(Ⅱ) released from GO-Pb(Ⅱ) was observed as lead phosphate hydroxide(Pb_(10)(PO_(4))_(6)(OH)_(2))precipitates or adsorbed species on the surface of the cell. Additionally, increasing pH induced the stripping of oxidative debris(OD) and elevated the content of dispersible Pb(Ⅱ)in aqueous solution under the conditions of S. putrefaciens metabolism. These research results provide valuable information regarding the migration of heavy metals adsorbed on GO under reducing conditions due to microbial metabolism.
基金supported financially by the National Natural Science Foundation of China(Grant No.22408083)Hebei Province modern agricultural industrial system characteristic seafood innovation team(HBCT2024290206).
文摘Shewanella putrefaciens(S.putrefaciens)is a key spoilage bacterium in aquatic products and exhibits a strong tendency to rot.Carnosic acid(CA)has attracted widespread attention as a natural antibacterial agent.In this study,we evaluated the antibacterial activity and mechanism of action of the natural antimicrobial agent CA against S.putrefaciens at the metabolic molecule level.The effect of CA on S.putrefaciens at the metabolic molecules level was analysed by using metabolomics.CA exhibited inhibited bacterial proliferation at a concentration of 0.2 mg/mL and completely killed bacteria at 0.4 mg/mL.Morphological analysis revealed fragmented cells with increased membrane permeability.This was accompanied by decreased respiratory metabolic viability and metabolic enzyme activity,suggesting that CA inhibited cellular respiration and energy synthesis of S.putrefaciens.Metabolomic analysis indicated that CA interfered with nucleotide metabolism,tricarboxylic acid cycle,biosynthesis of pantothenate and coenzyme A,and amino acid metabolism,and affected energy cycle,cell membrane structure,and expression of genetic material,which led to growth inhibition and bacterial death.These results indicate that CA exerts antibacterial effects by damaging the cell membrane,altering bacterial metabolism,and impairing oxidative respiration.We provide a theoretical basis for controlling S.putrefaciens and offer insights for improving the safety and shelf life of aquatic products.
基金supported by the National Key Research and Development Program of China(2023YFD2401402)the earmarked fund for CARS-47.
文摘Shewanella putrefaciens and Listeria monocytogenes are concerned by scientists and consumers due to their ability to produce dense biofilms to contaminate and cause food spoilage.The object of this study was to investigate the antimicrobial and anti-biofilm activities of octyl gallate(OG)against the two food-related bacteria.Results showed that the antimicrobial activities of OG were in a dose-dependent manner and the minimum inhibitory concentration(MIC)of S.putrefaciens and L.monocytogenes were 0.2 mmol/L and 0.1 mmol/L,respectively.OG can rapidly penetrate the bacteria and produce reactive oxygen species(ROS).Then,OG and ROS can lead to membrane damage and cell rupture,causing DNA and protein leakage.Our data also strongly suggested that OG not only can inhibit biofilms formation,but also eradicate the performed biofilms.Furthermore,it was shown that OG,as an additive,has great potential in antimicrobial application to prolong the shelf life of large yellow croakers.These prove that OG can combat bacteria and eradicate biofilm against S.putrefaciens and L.monocytogenes.
基金financially supported by the National Natural Science Foundation of China(No.32001801)the Program for Science&Technology Innovation Talents in Universities of Henan Province(No.24HASTIT058).
文摘This study investigated the antibacterial action of cinnamon essential oil(CEO)on Shewanella putrefaciens using untargeted metabolomics for the first time.The results demonstrated that CEO effectively suppressed the growth of S.putrefaciens with a minimal inhibition concentration(MIC)of 0.078μL/mL.CEO induced significant morphological and ultrastructural distortions in S.putrefaciens as well as serious damage to both the outer and inner membranes.Following exposure to CEO at 1×MIC,cell membrane permeability of S.putrefaciens increased significantly,as evidenced by a 5.10-fold rise in propidium iodide fluorescence intensity and a 0.39-fold increase in 1-N-phenylnaphthylamine fluorescence intensity compared to the control,along with membrane depolarization.These changes resulted in the leakage of crucial biological macromolecules,such as nucleic acids and proteins.Additionally,CEO at 1×MIC triggered the accumulation of reactive oxygen species by an 85.71%increase in 2′,7′-dichlorofluorescein diacetate fluorescence intensity within S.putrefaciens cells relative to the control,suggesting oxidative damage.Untargeted metabolomic analysis revealed that CEO at 1/2×MIC altered the metabolic profile,affecting several metabolic pathways,mainly including amino acid metabolism,nucleotide metabolism,glutathione metabolism,the one-carbon pool by folate,pantothenate and coenzyme A biosynthesis,and glycerophospholipid metabolism.These alterations could potentially disrupt nucleic acid metabolism,energy metabolism,and membrane stability,while activating the nucleotide salvage synthesis,sustaining redox homeostasis,and enhancing the overall adaptive capacity of S.putrefaciens.This study enhances the understanding of the antibacterial action of CEO and underscores its potential as a natural food preservative.
基金The study was financially supported by China Agriculture Research System(CARS-47-G26)Shanghai promote agriculture by applying scientific&technological advances projects(2015No.4e12)Ability promotion project of Shanghai Municipal Science and Technology Commission Engineering Center(16DZ2280300).
文摘The antimicrobial mechanism of Ginkgo biloba leaf extracts(GBLE)when applied to predominant spoilage bacteria(Shewanella putrefaciens and Saprophytic staphylococcus)on refrigerated pomfret and minimal inhibitory concentrations(MICs)were measured by the plate counting method.GBLE at MIC and 2MIC were prepared in tryptic soy broth(TSB)medium and equivalent amounts of sterile distilled water were used in place of GBLE as a control group.The impact of GBLE on the growth of bacteria,the permeability of cell membrane,and cell wall were also investigated by growth curve of bacteria,alkaline phosphates activity(AKP),and electrical conductivity.A scanning electron microscope(SEM)was used to study the effects of GBLE on the cellular structure of S.putrefaciens and S.staphylococcus.The results showed that the MICs of GBLE when applied to S.putrefaciens and S.staphylococcus were 100 mg/mL,the inhibitory rates of MIC and 2MIC concentrations of GBLE when applied to S.putrefaciens were 36.11%and 100%,while 27.78%and 62.22%for S.staphylococcus.Meanwhile,GBLE inhibited the growth of S.putrefaciens and S.staphylococcus until the number of cells at 2MIC values decreased to 0 and 4.29 log CFU/mL,respectively,after 24 h.The electrical conductivity of bacteria increased with GBLE treatment,which was followed by an increased leakage of AKP.The SEM revealed that the structure of bacterial cells was destroyed and the bacteria began to be adhere to each other.The inhibition effect of GBLE when applied to S.putrefaciens and S.staphylococcus was related to the damage of cell membrane and cell wall.It was also revealed that GBLE damages the morphology of bacteria and had stronger effects on the cell membrane of S.putrefaciens than that of S.staphylococcus.
基金This research was financially supported by National Natural Science Foundation of China(grant number:31972142,31571914)the earmarked fund for CARS-47the Shanghai Professional Technology Service Platform on Cold Chain Equipment Performance and Energy Saving Evaluation(20DZ2292200,19DZ1207503).
文摘Shewanella putrefaciens is one of the common spoilage microorganisms in aquatic products,and its extracellular protease is the main cause of seafood spoilage.The characteristics of the extracellular protease produced by S.putrefaciens YZ08 and its hydrolytic properties on fish proteins were studied.After purification,an extracellular protease of 18.78 kDa was obtained and identified as a metalloprotease of the M23 family.The gene encoding this enzyme was cloned and purified by expression in E.coli to obtain a recombinant protease.YZ08 protease showed optimum enzymatic activity at 40℃ and pH 9.0 and was stable at pH 7.0-10.0 and low temperature(<40℃).The kinetic parameters and thermal inactivation parameters of the enzyme were determined.S.putrefaciens YZ08 protease can degrade fish myofibrillar and sarcoplasmic proteins,breaking them down into small particles and low molecular peptides.The three-dimensional structure of the protease was simulated by homology modeling and revealed a correlation between the active site in the protein and substrate specificity.This work provides a foundation for characterizing the properties of S.putrefaciens YZ08 protease and for controlling the quality and safety of seafood.
基金supported by the Hainan Provincial Natural Science Foundation of China (321CXTD1012)the National Natural Science Foundation of China (NSFC31871868)the Scientific Research Foundation of Hainan Tropical Ocean University (RHDRC202117),China.
文摘Objectives:The bacteriostatic effects of a citral nanoemulsion against Shewanella putrefaciens CN-32(SHP CN-32)were investigated using in vitro culture and gene expression analysis,forbuilding a potential application in spoilage microorganism control and aquatic products quality maintenance.Materials and Methods:SHP CN-32 was treated by prepared citral nanoemulsion when the minimal inhibitory concentration(MIC)was verified.The growth curve,membrane integrity,scanning electron microscope(SEM)observation,biofilm formation and quorum sensing(QS)signaling molecule Al-2 content were evaluated in different MIC treatment groups(0 to 1.00 MIC).The gene expression status of SHP CN-32 in O and 0.50 MIC groups were compared using transcriptome sequencing and quantitative polymerase chain reaction(PCR).Results:The in vitro culture revealed that the citral nanoemulsion could inhibit the growth of SHP CN-32 with MIC of approximately 200μg/mL.Images of membrane integrity.SEM and biofilm formation suggested significant biological structure damage in bacteria after treatment.Meanwhile,the Qs signaling molecule Al-2 content showed a decline with increasing treatment concentration.Transcriptome sequencing and quantitative PCR revealed that the majority genes related diversified functional metabolic pathways of SHP CN-32 were downregulated at varying degree.Conclusion:A significant bacteriostasis of citral nanoemulsion against SHP CN-32 was verified via the results of growth inhibition,structural destruction,signal molecular decrease and gene expression downregulation of strains.These synergies significantly affect the characteristic expression of SHP CN-32,revealing the application potential as bacteriostat,QS inhibitor and preservative in aquatic products.
文摘We report a case of skin and soft tissue infection, peritonitis and bacteriemia in a 51-year-old drug abuse male. His wife found him lifeless lying on the kitchen floor at his residence. At the time of autopsy, multiple skin ulcers with deep soft tissue infection and peritonitis were found on gross examination. Cultures of postmortem blood and a swab of soft tissue were positive for Shewanella putrefaciens, a gram-negative bacterium that had been isolated from many foods, sewage and fresh and salt water. This is the first reported case in the United States of fatal skin and soft tissue infection, peritonitis and bacteremia caused by this micro-organism.
