Limits...
Identification of trkH, encoding a potassium uptake protein required for Francisella tularensis systemic dissemination in mice.

Alkhuder K, Meibom KL, Dubail I, Dupuis M, Charbit A - PLoS ONE (2010)

Bottom Line: Genome sequence analyses suggest that the Trk system constitutes the unique functional active potassium transporter in both tularensis and holarctica subspecies.Hence, the impaired survival of the trkH mutant in vivo is likely to be due to its inability to survive in the low potassium environment (1-5 mM range) of the blood.More generally, potassium could constitute an important mineral nutrient involved in other diseases linked to systemic dissemination of bacterial pathogens.

View Article: PubMed Central - PubMed

Affiliation: Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades, Paris, France.

ABSTRACT
Francisella tularensis is a highly infectious bacterium causing the zoonotic disease tularaemia. During its infectious cycle, F. tularensis is not only exposed to the intracellular environment of macrophages but also resides transiently in extracellular compartments, in particular during its systemic dissemination. The screening of a bank of F. tularensis LVS transposon insertion mutants on chemically defined medium (CDM) led us to identify a gene, designated trkH, encoding a homolog of the potassium uptake permease TrkH. Inactivation of trkH impaired bacterial growth in CDM. Normal growth of the mutant was only restored when CDM was supplemented with potassium at high concentration. Strikingly, although not required for intracellular survival in cell culture models, TrkH appeared to be essential for bacterial virulence in the mouse. In vivo kinetics of bacterial dissemination revealed a severe defect of multiplication of the trkH mutant in the blood of infected animals. The trkH mutant also showed impaired growth in blood ex vivo. Genome sequence analyses suggest that the Trk system constitutes the unique functional active potassium transporter in both tularensis and holarctica subspecies. Hence, the impaired survival of the trkH mutant in vivo is likely to be due to its inability to survive in the low potassium environment (1-5 mM range) of the blood. This work unravels thus the importance of potassium acquisition in the extracellular phase of the F. tularensis infectious cycle. More generally, potassium could constitute an important mineral nutrient involved in other diseases linked to systemic dissemination of bacterial pathogens.

Show MeSH

Related in: MedlinePlus

Multiplication of trkH mutant is impaired in murine blood ex vivo.Heparinized blood samples from eight mice were inoculated with ∼5×104 bacteria ml−1 and incubated at 37°C with shaking for 24 and 48 h, at which point the number of viable bacteria was determined. Closed symbols correspond to the LVS strain and open symbols the trkH mutant.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2813290&req=5

pone-0008966-g009: Multiplication of trkH mutant is impaired in murine blood ex vivo.Heparinized blood samples from eight mice were inoculated with ∼5×104 bacteria ml−1 and incubated at 37°C with shaking for 24 and 48 h, at which point the number of viable bacteria was determined. Closed symbols correspond to the LVS strain and open symbols the trkH mutant.

Mentions: To further examine the apparent decreased capacity of the trkH mutant to survive in host blood, we incubated LVS and trkH mutant bacteria in murine blood ex vivo. Heparinized blood collected from 8 mice was inoculated with LVS or trkH and the viable number of bacteria was determined after 24 and 48 h of incubation at 37°C. As had been observed previously [26], LVS multiplied and increased in numbers after incubation in murine blood (Figure 9). In contrast, the viable number of the trkH mutant was diminished considerably over the 48 h period, strongly indicating that the mutant fail to multiply in murine blood as the wild type parent strain.


Identification of trkH, encoding a potassium uptake protein required for Francisella tularensis systemic dissemination in mice.

Alkhuder K, Meibom KL, Dubail I, Dupuis M, Charbit A - PLoS ONE (2010)

Multiplication of trkH mutant is impaired in murine blood ex vivo.Heparinized blood samples from eight mice were inoculated with ∼5×104 bacteria ml−1 and incubated at 37°C with shaking for 24 and 48 h, at which point the number of viable bacteria was determined. Closed symbols correspond to the LVS strain and open symbols the trkH mutant.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2813290&req=5

pone-0008966-g009: Multiplication of trkH mutant is impaired in murine blood ex vivo.Heparinized blood samples from eight mice were inoculated with ∼5×104 bacteria ml−1 and incubated at 37°C with shaking for 24 and 48 h, at which point the number of viable bacteria was determined. Closed symbols correspond to the LVS strain and open symbols the trkH mutant.
Mentions: To further examine the apparent decreased capacity of the trkH mutant to survive in host blood, we incubated LVS and trkH mutant bacteria in murine blood ex vivo. Heparinized blood collected from 8 mice was inoculated with LVS or trkH and the viable number of bacteria was determined after 24 and 48 h of incubation at 37°C. As had been observed previously [26], LVS multiplied and increased in numbers after incubation in murine blood (Figure 9). In contrast, the viable number of the trkH mutant was diminished considerably over the 48 h period, strongly indicating that the mutant fail to multiply in murine blood as the wild type parent strain.

Bottom Line: Genome sequence analyses suggest that the Trk system constitutes the unique functional active potassium transporter in both tularensis and holarctica subspecies.Hence, the impaired survival of the trkH mutant in vivo is likely to be due to its inability to survive in the low potassium environment (1-5 mM range) of the blood.More generally, potassium could constitute an important mineral nutrient involved in other diseases linked to systemic dissemination of bacterial pathogens.

View Article: PubMed Central - PubMed

Affiliation: Université Paris Descartes, Faculté de Médecine Necker-Enfants Malades, Paris, France.

ABSTRACT
Francisella tularensis is a highly infectious bacterium causing the zoonotic disease tularaemia. During its infectious cycle, F. tularensis is not only exposed to the intracellular environment of macrophages but also resides transiently in extracellular compartments, in particular during its systemic dissemination. The screening of a bank of F. tularensis LVS transposon insertion mutants on chemically defined medium (CDM) led us to identify a gene, designated trkH, encoding a homolog of the potassium uptake permease TrkH. Inactivation of trkH impaired bacterial growth in CDM. Normal growth of the mutant was only restored when CDM was supplemented with potassium at high concentration. Strikingly, although not required for intracellular survival in cell culture models, TrkH appeared to be essential for bacterial virulence in the mouse. In vivo kinetics of bacterial dissemination revealed a severe defect of multiplication of the trkH mutant in the blood of infected animals. The trkH mutant also showed impaired growth in blood ex vivo. Genome sequence analyses suggest that the Trk system constitutes the unique functional active potassium transporter in both tularensis and holarctica subspecies. Hence, the impaired survival of the trkH mutant in vivo is likely to be due to its inability to survive in the low potassium environment (1-5 mM range) of the blood. This work unravels thus the importance of potassium acquisition in the extracellular phase of the F. tularensis infectious cycle. More generally, potassium could constitute an important mineral nutrient involved in other diseases linked to systemic dissemination of bacterial pathogens.

Show MeSH
Related in: MedlinePlus