Application of compost in agricultural practice could potentially cause contamination of foodstuffs with pathogenic bacteria such as Escherichia coli O157：H7 （E. Coli O157）. We investigated pathogenic bacteria in c...Application of compost in agricultural practice could potentially cause contamination of foodstuffs with pathogenic bacteria such as Escherichia coli O157：H7 （E. Coli O157）. We investigated pathogenic bacteria in compost collected from the compost facilities, and evaluated the survival of E. coli K12 and O157 in laboratory experiments. Out of 19 compost product samples, coliform bacteria and salmonella were detected in 7 and 3 samples respectively. The number of coliform bacteria was 1.8 × 10^2 to 2.5 × 10^6 CFU/g dw and that of salmonella was 4.2 × 10^1 to 6.0 × 10^3 CFU/g dw. Moreover. coliform bacteria, fecal coliform, E. coli and salmonella were detected during composting at 54℃ to 67℃. The results indicated that moisture content was a very important factor to the heat sensitivity of pathogenic bacteria in compost, E. coli in compost of high moisture content was more sensitive than that in compost of low moisture content, cells harvested in logarithmic phase was more sensitive than these in stationary phase, and E. coli K12 was more sensitive than E. coli O157. Based on the D values, the lethal time of E. coli K12 and 0157 from 10^8 to 10^0 CFU/g dw were 16.3 and 28.8 min, respectively, at 60℃ in compost with 40% moisture content. However, some E. coli cells survived in composting process at 54℃ to 67℃. Water potential（low moisture content） and physiological aspects of bacteria（stationary phase） could explain only in part of the prolonged survival of E. coli in compost, and there should be some other factors that are conducive to bacterial survial in compost.展开更多
The effects of antibacterial compounds produced by Saccharomyces cerevisiae in Koumiss on pathogenic Escherichia coli O8 and its cell surface characteristics were investigated.S.cerevisiae isolated from Koumiss produc...The effects of antibacterial compounds produced by Saccharomyces cerevisiae in Koumiss on pathogenic Escherichia coli O8 and its cell surface characteristics were investigated.S.cerevisiae isolated from Koumiss produced antibacterial compounds which were active against pathogenic E.coli O8 as determined by the Oxford cup method.The aqueous phases from S.cerevisiae at p H=2.0（S2）and pH=8.0（S8）were extracted and tested,respectively.The organic acids of S2 and S8 were determined by high performance liquid chromatography（HPLC）,and the concentrations of killer toxins were determined by enhanced bicinchoninic acid（BCA）Protein Assay Kit.The minimum inhibition concentration（MIC）and the minimum bactericidal concentration（MBC）of S2 and S8 on E.coli O8 were determined by the broth microdilution method.The effects of S2 and S8 on the growth curve of E.coli O8 were determined by turbidimetry,and the hydrophobicities of E.coli O8 cell surface were determined using the microbial adhesion to solvents method,the permeation of E.coli O8 cell membrane were determined by the o-nitrophenyl-β-D-galactoside（ONPG）method.Aqueous phases at pH 2.0 and 8.0had larger inhibition zones and then S2 and S8 were obtained by freeze-drying.The main component in S2 was citric acid and it was propanoic acid in S8.Other organic acids and killer toxins were also present.Both the MICs of S2 and S8 on E.coli O8 were 0.025 g m L^-1,the MBCs were 0.100 and 0.200 g m L^-1,respectively.The normal growth curve of E.coli O8was S-shaped,however,it changed after addition of S2 and S8.E.coli O8 was the basic character,and had a relatively hydrophilic surface.The hydrophobicity of E.coli O8 cell surface and the permeation of E.coli O8 cell membrane were increased after adding S2 and S8.The present study showed that S2 and S8 inhibit the growth of pathogenic E.coli O8and influence its cell surface characteristics.展开更多
[ Objective] To prepare recombinant type 1 pilus vaccine of avian Escherichia coil and to detect its immunogenicity in chickens. [Meth- od] The type 1 pilus was respectively isolated from the recombinant bacteria CZYR...[ Objective] To prepare recombinant type 1 pilus vaccine of avian Escherichia coil and to detect its immunogenicity in chickens. [Meth- od] The type 1 pilus was respectively isolated from the recombinant bacteria CZYR10 strain and wild avian Eschedchia co/i YR（ O18 ） strain and used to prepare oil-emulsified vaccine. The immunogenicity of the developed vaccine was detected in chickens using the challenge test. [ Result] The recombinant type 1 pilus protein had immunoprotective efficacy. The recombinant type 1 pilus protein had weaker protective efficacy than the isolated type 1 pilus protein, but the difference was not significant. [ Conclusion] The study provides a reference for immunization and control of chicken colibacillosis.展开更多
A multiplex polymerase chain reaction （PCR） was developed to detect three pathogenic genes of enteropathogenic, enterotocigenic and enteroinvasive Escherichia coli In this study three different sets of oligonucleoti...A multiplex polymerase chain reaction （PCR） was developed to detect three pathogenic genes of enteropathogenic, enterotocigenic and enteroinvasive Escherichia coli In this study three different sets of oligonucleotide primer were simultaneously used, and in this way, specific fragments of 880, 600, 150 bp for EPEC eaeA, EIEC ipaH and ETEC ST genes were amplified, respectively. The best condition of the multiplex PCR was： after an initial heat denaturation step at 95℃for 5 min, followed by 30 cycles of denaturation at 94 ℃ for 40 s, primer annealing at 51.3℃ for 40 s and extension at 72 ℃ for 1 min, final extension at 72 ℃ for 10 min. The detection limit of the eaeA, ipaH and ST primers was 38.7423, 3.60519, 29.9448 ng·mL^-1 （4.3×10^4, 1.5×10^3, 2.6×10^4 CFU·mL^-1）, respectively. It may be a good way for the detection and identification of Diarrhea-causing E. coli.展开更多
Objective The aim was to construct bioengineering strains that could degrade the cellulosic solid waste. Method The cDNA of endo-β-glucanase III of Trichoderma vi ride AS313711 was cloned by RT-PCR method. After sequ...Objective The aim was to construct bioengineering strains that could degrade the cellulosic solid waste. Method The cDNA of endo-β-glucanase III of Trichoderma vi ride AS313711 was cloned by RT-PCR method. After sequenced, this gene was constructed to expression vector pESP-2, and then the plasmid was transformed into competent cell of cerevisiae fermentum by electric shock, the transformant was then obtained. The enzyme activity of this transformant at the different temperatures and pH was measured by DNS method. Result The length of ORF of EG III was 1 257 bp, encoding 418 amino acids, while the deduced molecular weight was 44.1 × 103 kD. Conclusion The enzyme activity of EG III was the highest when it was at PH 4.9 and tempeture was of 60℃. Then the corresponding enzyme activity was about 100%.展开更多
文摘Application of compost in agricultural practice could potentially cause contamination of foodstuffs with pathogenic bacteria such as Escherichia coli O157：H7 （E. Coli O157）. We investigated pathogenic bacteria in compost collected from the compost facilities, and evaluated the survival of E. coli K12 and O157 in laboratory experiments. Out of 19 compost product samples, coliform bacteria and salmonella were detected in 7 and 3 samples respectively. The number of coliform bacteria was 1.8 × 10^2 to 2.5 × 10^6 CFU/g dw and that of salmonella was 4.2 × 10^1 to 6.0 × 10^3 CFU/g dw. Moreover. coliform bacteria, fecal coliform, E. coli and salmonella were detected during composting at 54℃ to 67℃. The results indicated that moisture content was a very important factor to the heat sensitivity of pathogenic bacteria in compost, E. coli in compost of high moisture content was more sensitive than that in compost of low moisture content, cells harvested in logarithmic phase was more sensitive than these in stationary phase, and E. coli K12 was more sensitive than E. coli O157. Based on the D values, the lethal time of E. coli K12 and 0157 from 10^8 to 10^0 CFU/g dw were 16.3 and 28.8 min, respectively, at 60℃ in compost with 40% moisture content. However, some E. coli cells survived in composting process at 54℃ to 67℃. Water potential（low moisture content） and physiological aspects of bacteria（stationary phase） could explain only in part of the prolonged survival of E. coli in compost, and there should be some other factors that are conducive to bacterial survial in compost.
基金supported by the National Natural Science Funds, China (31260570, 31260590, 31060318)the National Key Technologies R&D Program (2012BAD12B09-3)the Innovation Projects of Inner Mongolia Graduate Education, China (B20141012911)
文摘The effects of antibacterial compounds produced by Saccharomyces cerevisiae in Koumiss on pathogenic Escherichia coli O8 and its cell surface characteristics were investigated.S.cerevisiae isolated from Koumiss produced antibacterial compounds which were active against pathogenic E.coli O8 as determined by the Oxford cup method.The aqueous phases from S.cerevisiae at p H=2.0（S2）and pH=8.0（S8）were extracted and tested,respectively.The organic acids of S2 and S8 were determined by high performance liquid chromatography（HPLC）,and the concentrations of killer toxins were determined by enhanced bicinchoninic acid（BCA）Protein Assay Kit.The minimum inhibition concentration（MIC）and the minimum bactericidal concentration（MBC）of S2 and S8 on E.coli O8 were determined by the broth microdilution method.The effects of S2 and S8 on the growth curve of E.coli O8 were determined by turbidimetry,and the hydrophobicities of E.coli O8 cell surface were determined using the microbial adhesion to solvents method,the permeation of E.coli O8 cell membrane were determined by the o-nitrophenyl-β-D-galactoside（ONPG）method.Aqueous phases at pH 2.0 and 8.0had larger inhibition zones and then S2 and S8 were obtained by freeze-drying.The main component in S2 was citric acid and it was propanoic acid in S8.Other organic acids and killer toxins were also present.Both the MICs of S2 and S8 on E.coli O8 were 0.025 g m L^-1,the MBCs were 0.100 and 0.200 g m L^-1,respectively.The normal growth curve of E.coli O8was S-shaped,however,it changed after addition of S2 and S8.E.coli O8 was the basic character,and had a relatively hydrophilic surface.The hydrophobicity of E.coli O8 cell surface and the permeation of E.coli O8 cell membrane were increased after adding S2 and S8.The present study showed that S2 and S8 inhibit the growth of pathogenic E.coli O8and influence its cell surface characteristics.
基金funded by the Natural Science Foundation of Jiangsu Province ( BK2008059)
文摘[ Objective] To prepare recombinant type 1 pilus vaccine of avian Escherichia coil and to detect its immunogenicity in chickens. [Meth- od] The type 1 pilus was respectively isolated from the recombinant bacteria CZYR10 strain and wild avian Eschedchia co/i YR（ O18 ） strain and used to prepare oil-emulsified vaccine. The immunogenicity of the developed vaccine was detected in chickens using the challenge test. [ Result] The recombinant type 1 pilus protein had immunoprotective efficacy. The recombinant type 1 pilus protein had weaker protective efficacy than the isolated type 1 pilus protein, but the difference was not significant. [ Conclusion] The study provides a reference for immunization and control of chicken colibacillosis.
基金Key Item of National Technology Research Project (2002BA518A06)Heilongjiang Province Department Fund (10541021)
文摘A multiplex polymerase chain reaction （PCR） was developed to detect three pathogenic genes of enteropathogenic, enterotocigenic and enteroinvasive Escherichia coli In this study three different sets of oligonucleotide primer were simultaneously used, and in this way, specific fragments of 880, 600, 150 bp for EPEC eaeA, EIEC ipaH and ETEC ST genes were amplified, respectively. The best condition of the multiplex PCR was： after an initial heat denaturation step at 95℃for 5 min, followed by 30 cycles of denaturation at 94 ℃ for 40 s, primer annealing at 51.3℃ for 40 s and extension at 72 ℃ for 1 min, final extension at 72 ℃ for 10 min. The detection limit of the eaeA, ipaH and ST primers was 38.7423, 3.60519, 29.9448 ng·mL^-1 （4.3×10^4, 1.5×10^3, 2.6×10^4 CFU·mL^-1）, respectively. It may be a good way for the detection and identification of Diarrhea-causing E. coli.
文摘Objective The aim was to construct bioengineering strains that could degrade the cellulosic solid waste. Method The cDNA of endo-β-glucanase III of Trichoderma vi ride AS313711 was cloned by RT-PCR method. After sequenced, this gene was constructed to expression vector pESP-2, and then the plasmid was transformed into competent cell of cerevisiae fermentum by electric shock, the transformant was then obtained. The enzyme activity of this transformant at the different temperatures and pH was measured by DNS method. Result The length of ORF of EG III was 1 257 bp, encoding 418 amino acids, while the deduced molecular weight was 44.1 × 103 kD. Conclusion The enzyme activity of EG III was the highest when it was at PH 4.9 and tempeture was of 60℃. Then the corresponding enzyme activity was about 100%.
