SoxR, one of bacterial transcriptional regulators, plays a crucial role in bacterial responses to oxidative stress induced by unfavorable environmental conditions. So far, the understanding of bacterial responses to oxidative stress mainly stems from a handful model bacteria such as Escherichia coli and the studies on non-model bacterial responses to oxidative stress are limited. In this study, Citrobacter braakii JPG1, a commonly occurring strain of enterobacteria, was used as a model for the first time to explore the role of SoxR in the responses to aerobic/anaerobic-menadione stress. First, we analyzed the phylogenetic relationship of SoxR based on the whole genome and constructed the soxR-deleted strain (ΔsoxR). Then, the cell counts of the wild type (WT) and ΔsoxR were compared under aerobic/anaerobic-menadione stress. The results showed that the cell count of WT exposed to the aerobic-low concentration menadione (0.1 mmol/L) stress for 24 h increased by 4.2 times compared with that at the time point of 0 h, while that of ΔsoxR only increased by 1.3 times. The vast majority of WT and ΔsoxR cells died after exposure to the aerobic-high concentration menadione (0.3 mmol/L) stress for 24 h, with the cell counts only 29% and 0.2% of those at the time point of 0 h, respectively. Interestingly, the cell counts of WT showed no significant difference between the anaerobic-menadione stress and the control (P > 0.05), and the same was true for ΔsoxR. All these results indicated that SoxR of C. braakii JPG1 only has a regulatory effect on the redox cycling compound menadione under aerobic conditions and enhance the antioxidant capacity. Under anaerobic conditions, menadione failed to activate SoxR. The findings from this study provide new insights into understanding both the physiological responses to menadione stress and the regulatory role of SoxR under different oxygen conditions.
Bacterial Proteins/physiology* ; Anaerobiosis ; Aerobiosis ; Vitamin K 3/pharmacology* ; Citrobacter/metabolism* ; Transcription Factors/physiology* ; Oxidative Stress ; Gene Expression Regulation, Bacterial

BACKGROUND/AIMS: We evaluated changes of causative pathogen in acute cholangitis and their antimicrobial susceptibility over six years and differences between community-acquired and hospital-acquired acute cholangitis at our institution. METHODS: Medical records of 1,596 patients with acute cholangitis and biliary drainage between August 2006 and August 2012 were reviewed retrospectively. Cases were divided according to time: period 1 (August 2006-December 2008, n=645, 40.4%), period 2 (January 2009-August 2012, n=951, 59.6%). Cases were divided according to community-acquired cholangitis (n=1,397, 87.5%) and hospital-acquired cholangitis (n=199, 12.5%). Causative pathogens and antimicrobial susceptibility were investigated in each group. RESULTS: Causative pathogen was isolated from bile culture in 1,520 out of 1,596 cases (95.2%). The three most frequently isolated Gram-negative bacteria were extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli (n=485, 30.4%), E. coli (n=237, 13.2%), and Citrobacter freundii (n=110, 6.9%). Between periods 1 and 2, prevalence of ESBL-producing E. coli and Klebsiella pneumoniae did not show significant change (36.7% vs. 32.1%, p=0.073; 6.6% vs. 6.2%, p=0.732). C. freundii showed a significant increase from period 1 to period 2 (1.7% vs. 13.2%, p=0.000). In both time periods, imipenem was the antimicrobial agent showing the highest rate of susceptibility (93.3% vs. 93.9%, p=0.783). Higher prevalence of ESBL-producing E. coli and C. freundii was observed in the hospital-acquired cholangitis group (52.1% vs. 31.2%, p=0.000; 15.9% vs. 7.3%, p=0.001). CONCLUSIONS: The most common causative pathogen of acute cholangitis was ESBL-producing E. coli. Prevalence of C. freundii increased over the time period. Imipenem should be reserved as an alternative for resistant pathogens.
Acute Disease ; Aged ; Aged, 80 and over ; Anti-Bacterial Agents/*pharmacology ; Cholangitis/diagnosis/*microbiology ; *Citrobacter freundii/drug effects/isolation & purification ; Community-Acquired Infections/microbiology ; Cross Infection/microbiology ; Drug Resistance, Bacterial ; *Escherichia coli/drug effects/isolation & purification ; Female ; Humans ; Imipenem/pharmacology ; *Klebsiella pneumoniae/drug effects/isolation & purification ; Male ; Microbial Sensitivity Tests ; Middle Aged ; Retrospective Studies ; Time Factors ; beta-Lactamases/metabolism

No abstract available.
Aged ; Anti-Bacterial Agents/pharmacology/therapeutic use ; Asian Continental Ancestry Group ; Bacterial Proteins/genetics/*metabolism ; China ; Cilastatin/therapeutic use ; Citrobacter freundii/drug effects/*enzymology/isolation & purification ; Drug Combinations ; Drug Resistance, Multiple, Bacterial ; Humans ; Imipenem/therapeutic use ; Male ; Microbial Sensitivity Tests ; Plasmids/*metabolism ; Respiratory Tract Infections/*diagnosis/drug therapy/microbiology ; beta-Lactamases/genetics/*metabolism

No abstract available.
Aged ; Anti-Bacterial Agents/pharmacology/therapeutic use ; Cefotaxime/therapeutic use ; China ; Ciprofloxacin/therapeutic use ; Citrobacter freundii/drug effects/*enzymology/isolation & purification ; Drug Resistance, Multiple, Bacterial ; Humans ; Imipenem/pharmacology ; Male ; Microbial Sensitivity Tests ; Respiratory Tract Infections/*diagnosis/drug therapy/microbiology ; Thienamycins/pharmacology ; beta-Lactamases/*metabolism

The dhaB gene encoding glycerol dehydratase and dhaG dhaF gene encoding glycerol dehydratase reactivating factor from Citrobacterfreundii were amplified by PCR. The temperature control expression vector pHsh harboring yqhD, dhaB, dhaG and dhaF gene was transformed into E. coli JM109 to yield the recombinant strain E. coli JM109 (pHsh-dhaB-dhaG-dhaF-yqhD). The results from SDS-PAGE analysis show that the recombinant product was consistent with the molecular weight predicted from gene sequence. The fermentation result show that the yield of 1,3-propanediol was increased by 28% compared with E. coli JM109(pHsh-dhaB-yqhD).
Bacterial Proteins ; biosynthesis ; genetics ; Citrobacter freundii ; genetics ; metabolism ; Escherichia coli ; genetics ; metabolism ; Hydro-Lyases ; biosynthesis ; genetics ; Propylene Glycols ; metabolism ; Transformation, Bacterial ; genetics

The objective of this work was to develop a valuable adsorbent for recovery of platinum by studying the properties of Pt4+ -adsorption with immobilized Citrobacter freudii XP05 biomass. Five methods for immobilization of Citrobacter freudii XP05 biomass were compared. The method with gelatin-alginate sodium as entrapment matrix was considered to be the optimal. Spherical and uniform beads were produced and the SEM micrograph indicated that the cell of strain XP08 were uniformly dispersed within the matrix. The adsorption of Pt4+ by immobilized XP05 biomass was affected with adsorptive time, pH value of the solution, immobilized biomass concentration, Pt4+ initial concentration The adsorption was a rapid process. The optimal pH value for Pt4+ adsorption was 1.5, and its adsorptive capacity increased linearly with increasing Pt4+ initial concentrations in the range of 50 - 250 mg/L. The experimental data could be fitted to Langmuir and Freundlich models of adsorption isotherm. The adsorptive capacity reached 35.2 mg/g under the conditions of 250 Pt4+ mg/L, 2.0 g/L immobilized biomass, pH 1.5 and 30 degrees C for 60 min. 98.7% of Pt4+ adsorbed on immobilized biomass could be desorbed with 0.5 mol HC1/L. The characteristics of dynamic adsorption and desorption of immobilized XP05 biomass in packed-bed reactor were investigated. The saturation uptake was 24.66 mg Pt4+ /g under the conditions of flow rate 1.2 mL/min, pH 1.5, 50 mg Pt4+/L and 1.85 g biomass(dry weight) . Adsorptive efficiency of Pt4 + by the immobilized XP05 biomass was above 78% for 4 cycles of adsorption and desorption. The recovery of platinum from waste platinum catalyst was studied. The adsorptive capacity was 20.94 mg Pt4+/g immobilized biomass under the conditions of 4.0 g/L immobilized XP05 biomass, 117.76 mg Pt4+/L and pH 1.5 for 60 min. The immobilized XP05 biomass is potentially applicable to the recovery of platinum from waste and wastewater containing platinum.
Biomass ; Bioreactors ; microbiology ; Citrobacter ; metabolism ; Microscopy, Electron, Scanning ; Microspheres ; Platinum ; isolation & purification ; metabolism ; Waste Disposal, Fluid ; methods ; Water Pollutants, Chemical ; isolation & purification ; metabolism