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Differential Role of the T6SS in Acinetobacter baumannii Virulence.

Repizo GD, Gagné S, Foucault-Grunenwald ML, Borges V, Charpentier X, Limansky AS, Gomes JP, Viale AM, Salcedo SP - PLoS ONE (2015)

Bottom Line: The T6SS genomic locus is present and was actively transcribed in all of the above strains.In addition, DSM30011 was able to outcompete ATCC17978 as well as Pseudomonas aeruginosa and Klebsiella pneumoniae, bacterial pathogens relevant in mixed nosocomial infections.Finally, we found that the T6SS of DSM30011 is required for host colonization of the model organism Galleria mellonella suggesting that this system could play an important role in A. baumannii virulence in a strain-specific manner.

View Article: PubMed Central - PubMed

Affiliation: Bases Moléculaires et Structurales des Systèmes Infectieux, CNRS UMR 5086, Université Lyon 1, Institut de Biologie et Chimie des Protéines, Lyon, France.

ABSTRACT
Gram-negative bacteria, such as Acinetobacter baumannii, are an increasing burden in hospitals worldwide with an alarming spread of multi-drug resistant (MDR) strains. Herein, we compared a type strain (ATCC17978), a non-clinical isolate (DSM30011) and MDR strains of A. baumannii implicated in hospital outbreaks (Ab242, Ab244 and Ab825), revealing distinct patterns of type VI secretion system (T6SS) functionality. The T6SS genomic locus is present and was actively transcribed in all of the above strains. However, only the A. baumannii DSM30011 strain was capable of killing Escherichia coli in a T6SS-dependent manner, unlike the clinical isolates, which failed to display an active T6SS in vitro. In addition, DSM30011 was able to outcompete ATCC17978 as well as Pseudomonas aeruginosa and Klebsiella pneumoniae, bacterial pathogens relevant in mixed nosocomial infections. Finally, we found that the T6SS of DSM30011 is required for host colonization of the model organism Galleria mellonella suggesting that this system could play an important role in A. baumannii virulence in a strain-specific manner.

No MeSH data available.


Related in: MedlinePlus

The A. baumannii DSM30011 T6SS is required for out-competing E. coli.A) Representative image showing survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii ATCC17978 wild type and ΔtssM strains at a 1:1 ratio with or without the presence of a membrane (+M) and B) corresponding quantification (N = 6). C) Survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii DSM30011 wild type, ΔtssM and ΔtssM complemented strains at a 1:1 ratio, with D) corresponding quantification (N = 4). E) 18% SDS-PAGE (stained with Coomassie Blue) analysis of Hcp secretion in concentrated culture supernatants of A. baumannii DSM30011 wild type, ΔtssM and tssM complemented strains grown up to exponential phase in TSB. Molecular markers are indicated on the left. All quantifications are expressed as means ± SDM plotted in a logarithmic scale.
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pone.0138265.g003: The A. baumannii DSM30011 T6SS is required for out-competing E. coli.A) Representative image showing survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii ATCC17978 wild type and ΔtssM strains at a 1:1 ratio with or without the presence of a membrane (+M) and B) corresponding quantification (N = 6). C) Survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii DSM30011 wild type, ΔtssM and ΔtssM complemented strains at a 1:1 ratio, with D) corresponding quantification (N = 4). E) 18% SDS-PAGE (stained with Coomassie Blue) analysis of Hcp secretion in concentrated culture supernatants of A. baumannii DSM30011 wild type, ΔtssM and tssM complemented strains grown up to exponential phase in TSB. Molecular markers are indicated on the left. All quantifications are expressed as means ± SDM plotted in a logarithmic scale.

Mentions: In order to determine if the T6SS was responsible for the observed killing, ΔtssM deletion mutants in the ATCC17978 and DSM30011 backgrounds were tested. We observed no difference in E. coli killing for the ATCC17978 ΔtssM mutant with respect to the wild type (Fig 3A and 3B) consistent with what has been previously reported [10]. Interestingly, the T6SS-independent killing of E. coli by the A. baumannii ATCC17978 strain was contact-dependent as introduction of a membrane between the two strains completely abolished this phenotype (Fig 3A and 3B). It is worth noting that neither contact-dependent growth inhibition (CDI) systems nor additional T6SS were found encoded on the genome of ATCC17978.


Differential Role of the T6SS in Acinetobacter baumannii Virulence.

Repizo GD, Gagné S, Foucault-Grunenwald ML, Borges V, Charpentier X, Limansky AS, Gomes JP, Viale AM, Salcedo SP - PLoS ONE (2015)

The A. baumannii DSM30011 T6SS is required for out-competing E. coli.A) Representative image showing survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii ATCC17978 wild type and ΔtssM strains at a 1:1 ratio with or without the presence of a membrane (+M) and B) corresponding quantification (N = 6). C) Survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii DSM30011 wild type, ΔtssM and ΔtssM complemented strains at a 1:1 ratio, with D) corresponding quantification (N = 4). E) 18% SDS-PAGE (stained with Coomassie Blue) analysis of Hcp secretion in concentrated culture supernatants of A. baumannii DSM30011 wild type, ΔtssM and tssM complemented strains grown up to exponential phase in TSB. Molecular markers are indicated on the left. All quantifications are expressed as means ± SDM plotted in a logarithmic scale.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4581634&req=5

pone.0138265.g003: The A. baumannii DSM30011 T6SS is required for out-competing E. coli.A) Representative image showing survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii ATCC17978 wild type and ΔtssM strains at a 1:1 ratio with or without the presence of a membrane (+M) and B) corresponding quantification (N = 6). C) Survival of DH5α E. coli after incubation in growth medium (control) or with A. baumannii DSM30011 wild type, ΔtssM and ΔtssM complemented strains at a 1:1 ratio, with D) corresponding quantification (N = 4). E) 18% SDS-PAGE (stained with Coomassie Blue) analysis of Hcp secretion in concentrated culture supernatants of A. baumannii DSM30011 wild type, ΔtssM and tssM complemented strains grown up to exponential phase in TSB. Molecular markers are indicated on the left. All quantifications are expressed as means ± SDM plotted in a logarithmic scale.
Mentions: In order to determine if the T6SS was responsible for the observed killing, ΔtssM deletion mutants in the ATCC17978 and DSM30011 backgrounds were tested. We observed no difference in E. coli killing for the ATCC17978 ΔtssM mutant with respect to the wild type (Fig 3A and 3B) consistent with what has been previously reported [10]. Interestingly, the T6SS-independent killing of E. coli by the A. baumannii ATCC17978 strain was contact-dependent as introduction of a membrane between the two strains completely abolished this phenotype (Fig 3A and 3B). It is worth noting that neither contact-dependent growth inhibition (CDI) systems nor additional T6SS were found encoded on the genome of ATCC17978.

Bottom Line: The T6SS genomic locus is present and was actively transcribed in all of the above strains.In addition, DSM30011 was able to outcompete ATCC17978 as well as Pseudomonas aeruginosa and Klebsiella pneumoniae, bacterial pathogens relevant in mixed nosocomial infections.Finally, we found that the T6SS of DSM30011 is required for host colonization of the model organism Galleria mellonella suggesting that this system could play an important role in A. baumannii virulence in a strain-specific manner.

View Article: PubMed Central - PubMed

Affiliation: Bases Moléculaires et Structurales des Systèmes Infectieux, CNRS UMR 5086, Université Lyon 1, Institut de Biologie et Chimie des Protéines, Lyon, France.

ABSTRACT
Gram-negative bacteria, such as Acinetobacter baumannii, are an increasing burden in hospitals worldwide with an alarming spread of multi-drug resistant (MDR) strains. Herein, we compared a type strain (ATCC17978), a non-clinical isolate (DSM30011) and MDR strains of A. baumannii implicated in hospital outbreaks (Ab242, Ab244 and Ab825), revealing distinct patterns of type VI secretion system (T6SS) functionality. The T6SS genomic locus is present and was actively transcribed in all of the above strains. However, only the A. baumannii DSM30011 strain was capable of killing Escherichia coli in a T6SS-dependent manner, unlike the clinical isolates, which failed to display an active T6SS in vitro. In addition, DSM30011 was able to outcompete ATCC17978 as well as Pseudomonas aeruginosa and Klebsiella pneumoniae, bacterial pathogens relevant in mixed nosocomial infections. Finally, we found that the T6SS of DSM30011 is required for host colonization of the model organism Galleria mellonella suggesting that this system could play an important role in A. baumannii virulence in a strain-specific manner.

No MeSH data available.


Related in: MedlinePlus