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
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
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
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
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 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.
