Enterohemorrhagic Escherichia coli strains (EHEC) have caused many foodborne outbreaks. Bacterivorous protozoa could remove bacteria from aquatic systems. We analyzed the ciliate protozoan population changes influence...Enterohemorrhagic Escherichia coli strains (EHEC) have caused many foodborne outbreaks. Bacterivorous protozoa could remove bacteria from aquatic systems. We analyzed the ciliate protozoan population changes influenced by EHEC co-culture in activated sludge. EHEC and non-EHEC control E. coli cells were added to activated sludge samples in microcosms. The ciliate population changes were monitored by terminal restriction fragment length polymorphism (T-RFLP) analysis. EHEC and non-EHEC fed ciliate protozoan populations were different from each other and the no bacteria added controls based on the additive main effects and multiplicative interaction model (AMMI) analysis. Ciliate species were identified by 18S rDNA clone libraries. The 18S rDNA clones from the original sludge sample were identified as Epistylis wenrichi (70%) and Prorodon teres (30%), while clones from EHEC treated sludge sample were identified as P. teres (52%), Vorticella fusca (41%), Dexitrichides pangi (5%), and Opisthonecta henneguyi (2%). This study could provide helpful information about ciliate protozoan population changes caused by different E. coli strains in wastewater treatment plants, which could be useful for preventing and tracking E. coli outbreaks.展开更多
To construct and express the fusion protein Stx2B-IntiminC300 of EHEC O157 ： H7, and to further investigate its immunoprophylactic potential, the gene of Stx2B （stx2b） from EHEC O157：H7 chromosome was cloned into ...To construct and express the fusion protein Stx2B-IntiminC300 of EHEC O157 ： H7, and to further investigate its immunoprophylactic potential, the gene of Stx2B （stx2b） from EHEC O157：H7 chromosome was cloned into pMD18-T vector. Thereafter, the amplified gene was cloned into prokary- otic expression plasmid pET-28a （ ＋ ）-eaeC300, which was constructed previously. The recombinant pasmid pET-28a（ ＋ ）-stx2b-eaeC300 was transformed into E. coli BL21 （DE3）. After inducement, the protein Stx2B-IntiminC300 was successfully expressed and analyzed with sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE）, Western blotting and N-terminal amino acid residual sequencing. To evaluate its immunoprophylactic potential, it was primarily purified by ion-exchange chromatography and injected into 30 BALB/c mice with AI（OH）3 in the subscapular region. Ten days after the last booster vaccination, 20 mice were attacked with EHEC O157：H7 lysate and the protective efficacy was observed. In the present study, the gene of Stx2B-intiminC300 was successfully cloned into pET-28a （ ＋ ） vector. The results of SDS-PAGE and Western blotting assay showed that the fusion protein was successfully expressed in the inclusion body form, accounting for 25 % of total expression products, and its molecular weight was about 43 kDa. The result of the N-terminal amino acid residual sequencing showed that it was identical to that of the molecular designed. The purity was about 75 % after primary purification. Animal tests revealed that the fusion protein Stx2B-intiminC300 has elicited high titer of protective antibody relatively. These results demonstrate that the fusion protein Stx2B-IntiminC300 is successfully expressed in prokaryotic expression system and shows certain immunoprophylactic potential.展开更多
文摘Enterohemorrhagic Escherichia coli strains (EHEC) have caused many foodborne outbreaks. Bacterivorous protozoa could remove bacteria from aquatic systems. We analyzed the ciliate protozoan population changes influenced by EHEC co-culture in activated sludge. EHEC and non-EHEC control E. coli cells were added to activated sludge samples in microcosms. The ciliate population changes were monitored by terminal restriction fragment length polymorphism (T-RFLP) analysis. EHEC and non-EHEC fed ciliate protozoan populations were different from each other and the no bacteria added controls based on the additive main effects and multiplicative interaction model (AMMI) analysis. Ciliate species were identified by 18S rDNA clone libraries. The 18S rDNA clones from the original sludge sample were identified as Epistylis wenrichi (70%) and Prorodon teres (30%), while clones from EHEC treated sludge sample were identified as P. teres (52%), Vorticella fusca (41%), Dexitrichides pangi (5%), and Opisthonecta henneguyi (2%). This study could provide helpful information about ciliate protozoan population changes caused by different E. coli strains in wastewater treatment plants, which could be useful for preventing and tracking E. coli outbreaks.
文摘To construct and express the fusion protein Stx2B-IntiminC300 of EHEC O157 ： H7, and to further investigate its immunoprophylactic potential, the gene of Stx2B （stx2b） from EHEC O157：H7 chromosome was cloned into pMD18-T vector. Thereafter, the amplified gene was cloned into prokary- otic expression plasmid pET-28a （ ＋ ）-eaeC300, which was constructed previously. The recombinant pasmid pET-28a（ ＋ ）-stx2b-eaeC300 was transformed into E. coli BL21 （DE3）. After inducement, the protein Stx2B-IntiminC300 was successfully expressed and analyzed with sodium dodecyl sulfate polyacrylamide gel electrophoresis （SDS-PAGE）, Western blotting and N-terminal amino acid residual sequencing. To evaluate its immunoprophylactic potential, it was primarily purified by ion-exchange chromatography and injected into 30 BALB/c mice with AI（OH）3 in the subscapular region. Ten days after the last booster vaccination, 20 mice were attacked with EHEC O157：H7 lysate and the protective efficacy was observed. In the present study, the gene of Stx2B-intiminC300 was successfully cloned into pET-28a （ ＋ ） vector. The results of SDS-PAGE and Western blotting assay showed that the fusion protein was successfully expressed in the inclusion body form, accounting for 25 % of total expression products, and its molecular weight was about 43 kDa. The result of the N-terminal amino acid residual sequencing showed that it was identical to that of the molecular designed. The purity was about 75 % after primary purification. Animal tests revealed that the fusion protein Stx2B-intiminC300 has elicited high titer of protective antibody relatively. These results demonstrate that the fusion protein Stx2B-IntiminC300 is successfully expressed in prokaryotic expression system and shows certain immunoprophylactic potential.
