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IbeR facilitates stress-resistance, invasion and pathogenicity of avian pathogenic Escherichia coli.

Wang S, Bao Y, Meng Q, Xia Y, Zhao Y, Wang Y, Tang F, ZhuGe X, Yu S, Han X, Dai J, Lu C - PLoS ONE (2015)

Bottom Line: Inactivation of ibeR led to attenuated virulence and reduced invasion capacity towards DF-1 cells, brains and cerebrospinal fluid (CSF) in vitro and in vivo.These virulence-related phenotypes were restored by genetic complementation.Quantitative real-time reverse transcription PCR revealed that IbeR controlled expression of stress-resistance genes and virulence genes, which might led to the associated virulence phenotype.

View Article: PubMed Central - PubMed

Affiliation: Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, 200241, China; Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.

ABSTRACT
Systemic infections by avian pathogenic Escherichia coli (APEC) are economically devastating to poultry industries worldwide. IbeR, located on genomic island GimA, was shown to serve as an RpoS-like regulator in rpoS gene mutation neonatal meningitis E. coli (NMEC) RS218. However, the role of IbeR in pathogenicity of APEC carrying active RpoS has not yet been investigated. We showed that the APEC IbeR could elicit antibodies in infected ducks, suggesting that IbeR might be involved in APEC pathogenicity. To investigate the function of IbeR in APEC pathogenesis, mutant and complementation strains were constructed and characterized. Inactivation of ibeR led to attenuated virulence and reduced invasion capacity towards DF-1 cells, brains and cerebrospinal fluid (CSF) in vitro and in vivo. Bactericidal assays demonstrated that the mutant strain had impaired resistance to environmental stress and specific pathogen-free (SPF) chicken serum. These virulence-related phenotypes were restored by genetic complementation. Quantitative real-time reverse transcription PCR revealed that IbeR controlled expression of stress-resistance genes and virulence genes, which might led to the associated virulence phenotype.

No MeSH data available.


Related in: MedlinePlus

Bacterial resistance to environmental stress and SPF chicken serum.(A) Resistance to environmental stress. Each strain was tested for different environmental stress including alkali endurance (pH 10 for 30 min), acid endurance (acetic acid, pH 4.0 and pH 5.0 for 20 min) and high osmolarity challenge (2.4 M NaCl for 1 h). Results were expressed as survival relative to wild-type strain DE205B. Survival of ΔibeR was significantly lower than DE205B (* p < 0.05). The complementation strain CΔibeR recovered the most resistance. (B) Sensitivity to oxidants of DE205B and its ΔibeR and ΔibeA derivatives. Bacterial suspensions were treated with 10 mM H2O2 at 37°C for 30 min. After stress exposure, bacteria were diluted in PBS and plated on LB agar. The data were expressed as survival relative to wild-type strain DE205B. Mutant strains ΔibeR, ΔibeA, ΔibeRibeA were more sensitive to H2O2 killing than the wild type strain DE205B (** p < 0.01; *** p < 0.001). Moreover, the resistance to H2O2 was restored for the complementation strains. (C) Resistance to SPF chicken serum. Bacteria were incubated at 37°C with SPF chicken serum at different dilutions, and counted at 30 min. Mutant strain ΔibeR showed significantly reduced resistance to SPF chicken serum compared to DE205B (* p < 0.05). The error bars indicate standard deviations.
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pone.0119698.g002: Bacterial resistance to environmental stress and SPF chicken serum.(A) Resistance to environmental stress. Each strain was tested for different environmental stress including alkali endurance (pH 10 for 30 min), acid endurance (acetic acid, pH 4.0 and pH 5.0 for 20 min) and high osmolarity challenge (2.4 M NaCl for 1 h). Results were expressed as survival relative to wild-type strain DE205B. Survival of ΔibeR was significantly lower than DE205B (* p < 0.05). The complementation strain CΔibeR recovered the most resistance. (B) Sensitivity to oxidants of DE205B and its ΔibeR and ΔibeA derivatives. Bacterial suspensions were treated with 10 mM H2O2 at 37°C for 30 min. After stress exposure, bacteria were diluted in PBS and plated on LB agar. The data were expressed as survival relative to wild-type strain DE205B. Mutant strains ΔibeR, ΔibeA, ΔibeRibeA were more sensitive to H2O2 killing than the wild type strain DE205B (** p < 0.01; *** p < 0.001). Moreover, the resistance to H2O2 was restored for the complementation strains. (C) Resistance to SPF chicken serum. Bacteria were incubated at 37°C with SPF chicken serum at different dilutions, and counted at 30 min. Mutant strain ΔibeR showed significantly reduced resistance to SPF chicken serum compared to DE205B (* p < 0.05). The error bars indicate standard deviations.

Mentions: The role of IbeR in bacterial resistance to environmental stresses including alkali endurance (pH 10 for 30 min), acid endurance (acetic acid, pH 4.0 and pH 5.0 for 20 min) and high osmolarity challenge (2.4 M NaCl for 1 h) were determined. In all experiments, survival of wild-type strain DE205B was higher than the mutant strain ΔibeR (Fig. 2A), indicating that IbeR was required for stress-resistance. Previous study showed that GimA and IbeA paly a role in H2O2 stress-resistance [34]. Thus, the resistance to H2O2 stress of each strain was determined. The results showed that mutant strains ΔibeR, ΔibeA, ΔibeRibeA were more sensitive to H2O2 killing than the wild type strain DE205B. Moreover, the resistance to H2O2 was restored for the complementation strains (Fig. 2B). Thus, our results indicated that the deletion of ibeR was responsible for the lower resistance to H2O2 and other environmental stresses of the mutant strain ΔibeR.


IbeR facilitates stress-resistance, invasion and pathogenicity of avian pathogenic Escherichia coli.

Wang S, Bao Y, Meng Q, Xia Y, Zhao Y, Wang Y, Tang F, ZhuGe X, Yu S, Han X, Dai J, Lu C - PLoS ONE (2015)

Bacterial resistance to environmental stress and SPF chicken serum.(A) Resistance to environmental stress. Each strain was tested for different environmental stress including alkali endurance (pH 10 for 30 min), acid endurance (acetic acid, pH 4.0 and pH 5.0 for 20 min) and high osmolarity challenge (2.4 M NaCl for 1 h). Results were expressed as survival relative to wild-type strain DE205B. Survival of ΔibeR was significantly lower than DE205B (* p < 0.05). The complementation strain CΔibeR recovered the most resistance. (B) Sensitivity to oxidants of DE205B and its ΔibeR and ΔibeA derivatives. Bacterial suspensions were treated with 10 mM H2O2 at 37°C for 30 min. After stress exposure, bacteria were diluted in PBS and plated on LB agar. The data were expressed as survival relative to wild-type strain DE205B. Mutant strains ΔibeR, ΔibeA, ΔibeRibeA were more sensitive to H2O2 killing than the wild type strain DE205B (** p < 0.01; *** p < 0.001). Moreover, the resistance to H2O2 was restored for the complementation strains. (C) Resistance to SPF chicken serum. Bacteria were incubated at 37°C with SPF chicken serum at different dilutions, and counted at 30 min. Mutant strain ΔibeR showed significantly reduced resistance to SPF chicken serum compared to DE205B (* p < 0.05). The error bars indicate standard deviations.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4359115&req=5

pone.0119698.g002: Bacterial resistance to environmental stress and SPF chicken serum.(A) Resistance to environmental stress. Each strain was tested for different environmental stress including alkali endurance (pH 10 for 30 min), acid endurance (acetic acid, pH 4.0 and pH 5.0 for 20 min) and high osmolarity challenge (2.4 M NaCl for 1 h). Results were expressed as survival relative to wild-type strain DE205B. Survival of ΔibeR was significantly lower than DE205B (* p < 0.05). The complementation strain CΔibeR recovered the most resistance. (B) Sensitivity to oxidants of DE205B and its ΔibeR and ΔibeA derivatives. Bacterial suspensions were treated with 10 mM H2O2 at 37°C for 30 min. After stress exposure, bacteria were diluted in PBS and plated on LB agar. The data were expressed as survival relative to wild-type strain DE205B. Mutant strains ΔibeR, ΔibeA, ΔibeRibeA were more sensitive to H2O2 killing than the wild type strain DE205B (** p < 0.01; *** p < 0.001). Moreover, the resistance to H2O2 was restored for the complementation strains. (C) Resistance to SPF chicken serum. Bacteria were incubated at 37°C with SPF chicken serum at different dilutions, and counted at 30 min. Mutant strain ΔibeR showed significantly reduced resistance to SPF chicken serum compared to DE205B (* p < 0.05). The error bars indicate standard deviations.
Mentions: The role of IbeR in bacterial resistance to environmental stresses including alkali endurance (pH 10 for 30 min), acid endurance (acetic acid, pH 4.0 and pH 5.0 for 20 min) and high osmolarity challenge (2.4 M NaCl for 1 h) were determined. In all experiments, survival of wild-type strain DE205B was higher than the mutant strain ΔibeR (Fig. 2A), indicating that IbeR was required for stress-resistance. Previous study showed that GimA and IbeA paly a role in H2O2 stress-resistance [34]. Thus, the resistance to H2O2 stress of each strain was determined. The results showed that mutant strains ΔibeR, ΔibeA, ΔibeRibeA were more sensitive to H2O2 killing than the wild type strain DE205B. Moreover, the resistance to H2O2 was restored for the complementation strains (Fig. 2B). Thus, our results indicated that the deletion of ibeR was responsible for the lower resistance to H2O2 and other environmental stresses of the mutant strain ΔibeR.

Bottom Line: Inactivation of ibeR led to attenuated virulence and reduced invasion capacity towards DF-1 cells, brains and cerebrospinal fluid (CSF) in vitro and in vivo.These virulence-related phenotypes were restored by genetic complementation.Quantitative real-time reverse transcription PCR revealed that IbeR controlled expression of stress-resistance genes and virulence genes, which might led to the associated virulence phenotype.

View Article: PubMed Central - PubMed

Affiliation: Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, 200241, China; Key Lab of Animal Bacteriology, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.

ABSTRACT
Systemic infections by avian pathogenic Escherichia coli (APEC) are economically devastating to poultry industries worldwide. IbeR, located on genomic island GimA, was shown to serve as an RpoS-like regulator in rpoS gene mutation neonatal meningitis E. coli (NMEC) RS218. However, the role of IbeR in pathogenicity of APEC carrying active RpoS has not yet been investigated. We showed that the APEC IbeR could elicit antibodies in infected ducks, suggesting that IbeR might be involved in APEC pathogenicity. To investigate the function of IbeR in APEC pathogenesis, mutant and complementation strains were constructed and characterized. Inactivation of ibeR led to attenuated virulence and reduced invasion capacity towards DF-1 cells, brains and cerebrospinal fluid (CSF) in vitro and in vivo. Bactericidal assays demonstrated that the mutant strain had impaired resistance to environmental stress and specific pathogen-free (SPF) chicken serum. These virulence-related phenotypes were restored by genetic complementation. Quantitative real-time reverse transcription PCR revealed that IbeR controlled expression of stress-resistance genes and virulence genes, which might led to the associated virulence phenotype.

No MeSH data available.


Related in: MedlinePlus