Enterobacter cloacae CYS-25 strain was isolated from a chromate plant. This bacterium was capable of resisting high hexavalent chromium concentration and reducing Cr(VI) under aerobic condition. CrO4^2- stimulated t...Enterobacter cloacae CYS-25 strain was isolated from a chromate plant. This bacterium was capable of resisting high hexavalent chromium concentration and reducing Cr(VI) under aerobic condition. CrO4^2- stimulated the increase of bacterial size and production of compact convex paths containing chromium on the bacterial surface. The increase of bacterial size was caused by integrative growth but not extracellular polymeric substance hyperplasia. IR and SDS-PAGE analyses showed the extracellular polymeric substance (EPS) components were mainly proteins and had no obvious changes whether the strains were induced by Cr(VI) or not. The EPS was amorphous and contained trivalent chromium. Under CrO4^2- growth condition, the extracellular substance of Enterobacter cloacae CYS-25 strains and Cr(VI) had redox reaction. The products were Cr^3*-protein complexes which formed a piece of compact convex paths on the surface of bacteria and prevented Cr(VI) from entering into cells.展开更多
This study focused on the screening of cadmium-resistant bacterial strains from Pb-Zn tailing. We investigated the diversity of microbial community inhabiting Dong-san-cha Pb-Zn tailing in Beijing, China, by polymeras...This study focused on the screening of cadmium-resistant bacterial strains from Pb-Zn tailing. We investigated the diversity of microbial community inhabiting Dong-san-cha Pb-Zn tailing in Beijing, China, by polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene of bacterial strain, and found two dominant strains in the DGGE profile. Using special culture media, we isolated two strong cadmium-resistant bacterial strains. On the basis of morphological, physiological, and biochemical characteristics, BIOLOG, and 16S rDNA sequencing, the two strains were identified as Bacillus cereus and Enterobacter cloacae. Minimal inhibitory concentrations (MICs) of heavy metals for the bacteria were determined. E. cloacae showed higher MIC values for heavy metals and a larger range of antibiotic resistance than B. cereus.展开更多
Objective To investigate the status of the drug resistance and the ampC gene expression of Enterobacter cloacae . Methods Disk diffusion tests were made for detecting the susceptibility of antimicrobial agents agai...Objective To investigate the status of the drug resistance and the ampC gene expression of Enterobacter cloacae . Methods Disk diffusion tests were made for detecting the susceptibility of antimicrobial agents against Enterobacter cloacae . AmpC gene was amplified by polymerase chain reaction (PCR) and verified by DNA sequencing. AmpC gene expression was analyzed according to antimicrobial agent sensitive phenotype. Results The sensitivity rates of 144 strains to imipenam,cefepime and cefoperazone/sulbactam were 98.61%,65.97% and 63.89%,respectively. The sensitivity rates of 144 strains to other antimicrobial agents were lower. Among the 144 strains 120 were found to be positive by PCR for ampC. The PCR product showed high homology to the GenBank ampC sequence. Stably derepressed strains,hyperinducible strains and unexpressing or lower level expressing strains accounted for 30.0% (36/120),37.5% (45/120),and 32.5% (39/120),respectively. Fifty-six out of 120 strains (46.67%) also produced extended spectrum β-lactamases (ESBLs). The hyperinducible strains were highly sensitive to all the antimicrobial agents except amoxicillin/clavulanic acid and cefuroxime,while the stably derepressed strains were only sensitive to imipenam and cefepime. However,sensitivity to cefepime decreased if the strains also produced ESBLs. Conclusions The durg resistant status of Enterobacter cloacae is severe. Clearing out the expressive status of ampC gene will be helpful in selection of antimicrobial agents in the treatment of clinical infection.展开更多
In order to provide useful information for effective control and clinical therapy of infection,the resistance status and the rate of carrying AmpC β-lactamase of Enterobacter cloacae(E.cloacae)were investigated.By VI...In order to provide useful information for effective control and clinical therapy of infection,the resistance status and the rate of carrying AmpC β-lactamase of Enterobacter cloacae(E.cloacae)were investigated.By VITEK(Bacterial automatic biochemical analyzer),the isolates of E.cloacae were identified and the drug resistance was measured.The AmpC enzyme was detected by thefive-disk diffusion test.Antibiotic sensitivity test showed that the resistance effects of E.cloacae to cefazolin,cefoxitin and ampicillin were more serious,with resistant rates of 80.5%,75.3%and 70.1%,respectively.However,it was more sensitive to Sulperazone(cefoperazone/sulbactam,13.0%),amikacin(16.9%)and ciprofloxacin(19.5%).Meanwhile,the phenotype detection showed that 35.06%(27/77)isolates of E.cloacae produced AmpCβ-lactamase.Most of E.cloacae are multi-drug resistant strains.Sulperazone(cefoperazone/sulbactam),a kind of componentβ-lactamase,is a more effective antibiotic for treating infection caused by E.cloacae.Unreasonable application of the third generation cephalosporins plays an important role in leading to emergence of high-yield AmpCβ-lactamase strains,so antibiotics should be used wisely.展开更多
Atrazine is a selective herbicide used in agricultural fields to control the emergence of broadleaf and grassy weeds. The persistence of this herbicide is influenced by the metabolic action of habituated native microo...Atrazine is a selective herbicide used in agricultural fields to control the emergence of broadleaf and grassy weeds. The persistence of this herbicide is influenced by the metabolic action of habituated native microorganisms. This study provides information on the occurrence of atrazine mineralizing bacterial strains with faster metabolizing ability. The enrichment cultures were tested for the biodegradation of atrazine by high-performance liquid chromatography(HPLC) and mass spectrometry. Nine cultures JS01.Deg01 to JS09.Deg01 were identified as the degrader of atrazine in the enrichment culture. The three isolates JS04.Deg01, JS07.Deg01, and JS08.Deg01 were identified as efficient atrazine metabolizers. Isolates JS04.Deg01 and JS07.Deg01 produced hydroxyatrazine(HA) N-isopropylammelide and cyanuric acid by dealkylation reaction. The isolate JS08.Deg01 generated deethylatrazine(DEA), deisopropylatrazine(DIA), and cyanuric acid by N-dealkylation in the upper degradation pathway and later it incorporated cyanuric acid in their biomass by the lower degradation pathway. The optimum pH for degrading atrazine by JS08.Deg01 was 7.0 and 16S rDNA phylogenetic typing identified it as Enterobacter cloacae strain JS08.Deg01. The highest atrazine mineralization was observed in case of isolate JS08.Deg01, where an ample amount of trzD mRNA was quantified at 72 h of incubation with atrazine. Atrazine bioremediating isolate E. cloacae strain JS08.Deg01 could be the better environmental remediator of agricultural soils and the crop fields contaminated with atrazine could be the source of the efficient biodegrading microbial strains for the environmental cleanup process.展开更多
基金This work was supported by the National Natural Science Foundation of China (20501020, 40772034) Nanoscience Foundation of China (90406024)+2 种基金Natural Science Foundation of Fujian Province (No. X0650094/2006J0383)973 program (2007CB815601) the Special Project on Science and Technology of Fujian Province (2005YZ1026)
文摘Enterobacter cloacae CYS-25 strain was isolated from a chromate plant. This bacterium was capable of resisting high hexavalent chromium concentration and reducing Cr(VI) under aerobic condition. CrO4^2- stimulated the increase of bacterial size and production of compact convex paths containing chromium on the bacterial surface. The increase of bacterial size was caused by integrative growth but not extracellular polymeric substance hyperplasia. IR and SDS-PAGE analyses showed the extracellular polymeric substance (EPS) components were mainly proteins and had no obvious changes whether the strains were induced by Cr(VI) or not. The EPS was amorphous and contained trivalent chromium. Under CrO4^2- growth condition, the extracellular substance of Enterobacter cloacae CYS-25 strains and Cr(VI) had redox reaction. The products were Cr^3*-protein complexes which formed a piece of compact convex paths on the surface of bacteria and prevented Cr(VI) from entering into cells.
基金Project supported by the National Natural Science Foundation of China(No. 20477051, 20521140076).
文摘This study focused on the screening of cadmium-resistant bacterial strains from Pb-Zn tailing. We investigated the diversity of microbial community inhabiting Dong-san-cha Pb-Zn tailing in Beijing, China, by polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene of bacterial strain, and found two dominant strains in the DGGE profile. Using special culture media, we isolated two strong cadmium-resistant bacterial strains. On the basis of morphological, physiological, and biochemical characteristics, BIOLOG, and 16S rDNA sequencing, the two strains were identified as Bacillus cereus and Enterobacter cloacae. Minimal inhibitory concentrations (MICs) of heavy metals for the bacteria were determined. E. cloacae showed higher MIC values for heavy metals and a larger range of antibiotic resistance than B. cereus.
文摘Objective To investigate the status of the drug resistance and the ampC gene expression of Enterobacter cloacae . Methods Disk diffusion tests were made for detecting the susceptibility of antimicrobial agents against Enterobacter cloacae . AmpC gene was amplified by polymerase chain reaction (PCR) and verified by DNA sequencing. AmpC gene expression was analyzed according to antimicrobial agent sensitive phenotype. Results The sensitivity rates of 144 strains to imipenam,cefepime and cefoperazone/sulbactam were 98.61%,65.97% and 63.89%,respectively. The sensitivity rates of 144 strains to other antimicrobial agents were lower. Among the 144 strains 120 were found to be positive by PCR for ampC. The PCR product showed high homology to the GenBank ampC sequence. Stably derepressed strains,hyperinducible strains and unexpressing or lower level expressing strains accounted for 30.0% (36/120),37.5% (45/120),and 32.5% (39/120),respectively. Fifty-six out of 120 strains (46.67%) also produced extended spectrum β-lactamases (ESBLs). The hyperinducible strains were highly sensitive to all the antimicrobial agents except amoxicillin/clavulanic acid and cefuroxime,while the stably derepressed strains were only sensitive to imipenam and cefepime. However,sensitivity to cefepime decreased if the strains also produced ESBLs. Conclusions The durg resistant status of Enterobacter cloacae is severe. Clearing out the expressive status of ampC gene will be helpful in selection of antimicrobial agents in the treatment of clinical infection.
基金supported by the Key Subject of Tianjin Medical University(No.2004xk47).
文摘In order to provide useful information for effective control and clinical therapy of infection,the resistance status and the rate of carrying AmpC β-lactamase of Enterobacter cloacae(E.cloacae)were investigated.By VITEK(Bacterial automatic biochemical analyzer),the isolates of E.cloacae were identified and the drug resistance was measured.The AmpC enzyme was detected by thefive-disk diffusion test.Antibiotic sensitivity test showed that the resistance effects of E.cloacae to cefazolin,cefoxitin and ampicillin were more serious,with resistant rates of 80.5%,75.3%and 70.1%,respectively.However,it was more sensitive to Sulperazone(cefoperazone/sulbactam,13.0%),amikacin(16.9%)and ciprofloxacin(19.5%).Meanwhile,the phenotype detection showed that 35.06%(27/77)isolates of E.cloacae produced AmpCβ-lactamase.Most of E.cloacae are multi-drug resistant strains.Sulperazone(cefoperazone/sulbactam),a kind of componentβ-lactamase,is a more effective antibiotic for treating infection caused by E.cloacae.Unreasonable application of the third generation cephalosporins plays an important role in leading to emergence of high-yield AmpCβ-lactamase strains,so antibiotics should be used wisely.
文摘Atrazine is a selective herbicide used in agricultural fields to control the emergence of broadleaf and grassy weeds. The persistence of this herbicide is influenced by the metabolic action of habituated native microorganisms. This study provides information on the occurrence of atrazine mineralizing bacterial strains with faster metabolizing ability. The enrichment cultures were tested for the biodegradation of atrazine by high-performance liquid chromatography(HPLC) and mass spectrometry. Nine cultures JS01.Deg01 to JS09.Deg01 were identified as the degrader of atrazine in the enrichment culture. The three isolates JS04.Deg01, JS07.Deg01, and JS08.Deg01 were identified as efficient atrazine metabolizers. Isolates JS04.Deg01 and JS07.Deg01 produced hydroxyatrazine(HA) N-isopropylammelide and cyanuric acid by dealkylation reaction. The isolate JS08.Deg01 generated deethylatrazine(DEA), deisopropylatrazine(DIA), and cyanuric acid by N-dealkylation in the upper degradation pathway and later it incorporated cyanuric acid in their biomass by the lower degradation pathway. The optimum pH for degrading atrazine by JS08.Deg01 was 7.0 and 16S rDNA phylogenetic typing identified it as Enterobacter cloacae strain JS08.Deg01. The highest atrazine mineralization was observed in case of isolate JS08.Deg01, where an ample amount of trzD mRNA was quantified at 72 h of incubation with atrazine. Atrazine bioremediating isolate E. cloacae strain JS08.Deg01 could be the better environmental remediator of agricultural soils and the crop fields contaminated with atrazine could be the source of the efficient biodegrading microbial strains for the environmental cleanup process.