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Expression of the Genes Encoding the Trk and Kdp Potassium Transport Systems of Mycobacterium tuberculosis during Growth In Vitro.

Cholo MC, van Rensburg EJ, Osman AG, Anderson R - Biomed Res Int (2015)

Bottom Line: In both strains, mRNA levels of the K(+)-uptake encoding genes were relatively low compared to those of the housekeeping gene, sigA, at the early- and mid-log phases, increasing during late-log.Increased gene expression coincided with decreased K(+) uptake in the context of a drop in extracellular pH and sustained high extracellular K(+) concentrations.Decreasing the pH resulted in reductions in both membrane potential and K(+) uptake in the setting of significant induction of genes encoding both K(+) transporters.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria 0001, South Africa.

ABSTRACT
Two potassium (K(+))-uptake systems, Trk and Kdp, are operative in Mycobacterium tuberculosis (Mtb), but the environmental factors triggering their expression have not been determined. The current study has evaluated the expression of these genes in the Mtb wild-type and a trk-gene knockout strain at various stages of logarithmic growth in relation to extracellular K(+) concentrations and pH. In both strains, mRNA levels of the K(+)-uptake encoding genes were relatively low compared to those of the housekeeping gene, sigA, at the early- and mid-log phases, increasing during late-log. Increased gene expression coincided with decreased K(+) uptake in the context of a drop in extracellular pH and sustained high extracellular K(+) concentrations. In an additional series of experiments, the pH of the growth medium was manipulated by the addition of 1N HCl/NaOH. Decreasing the pH resulted in reductions in both membrane potential and K(+) uptake in the setting of significant induction of genes encoding both K(+) transporters. These observations are consistent with induction of the genes encoding the active K(+) transporters of Mtb as a strategy to compensate for loss of membrane potential-driven uptake of K(+) at low extracellular pH. Induction of these genes may promote survival in the acidic environments of the intracellular vacuole and granuloma.

No MeSH data available.


Related in: MedlinePlus

86Rb+-uptake efficiencies of the WT and trk-gene knockout strains at the mid- and late-log phases. The results are of three separate experiments with a total of 10–15 replicates for the mid- and late-log phases, respectively. Statistical significance was determined between the two strains within each growth phase and for each strain between the two growth phases. ∗p < 0.05. The absolute radioactive cpm values were 91041 ± 10465 and 148615 ± 9918 and 42431 ± 3447 and 88819 ± 8178 for WT and trk-gene knockout strains at mid- and late-log phases, respectively.
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fig1: 86Rb+-uptake efficiencies of the WT and trk-gene knockout strains at the mid- and late-log phases. The results are of three separate experiments with a total of 10–15 replicates for the mid- and late-log phases, respectively. Statistical significance was determined between the two strains within each growth phase and for each strain between the two growth phases. ∗p < 0.05. The absolute radioactive cpm values were 91041 ± 10465 and 148615 ± 9918 and 42431 ± 3447 and 88819 ± 8178 for WT and trk-gene knockout strains at mid- and late-log phases, respectively.

Mentions: The efficiencies in K+ uptake of the two strains during the mid- and late-log phases were determined by measuring the absolute uptake of 86Rb+ by the strains during these growth phases. The results are represented as the mean radioactive counts per minute (cpm) values ± SEM and are shown in Figure 1. During both growth phases, the 86Rb+-uptake efficiencies of the trk-gene knockout strain were higher than those of the WT strain. However, the K+-uptake efficiencies of both strains were reduced as the bacteria entered the late-log phase.


Expression of the Genes Encoding the Trk and Kdp Potassium Transport Systems of Mycobacterium tuberculosis during Growth In Vitro.

Cholo MC, van Rensburg EJ, Osman AG, Anderson R - Biomed Res Int (2015)

86Rb+-uptake efficiencies of the WT and trk-gene knockout strains at the mid- and late-log phases. The results are of three separate experiments with a total of 10–15 replicates for the mid- and late-log phases, respectively. Statistical significance was determined between the two strains within each growth phase and for each strain between the two growth phases. ∗p < 0.05. The absolute radioactive cpm values were 91041 ± 10465 and 148615 ± 9918 and 42431 ± 3447 and 88819 ± 8178 for WT and trk-gene knockout strains at mid- and late-log phases, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4553272&req=5

fig1: 86Rb+-uptake efficiencies of the WT and trk-gene knockout strains at the mid- and late-log phases. The results are of three separate experiments with a total of 10–15 replicates for the mid- and late-log phases, respectively. Statistical significance was determined between the two strains within each growth phase and for each strain between the two growth phases. ∗p < 0.05. The absolute radioactive cpm values were 91041 ± 10465 and 148615 ± 9918 and 42431 ± 3447 and 88819 ± 8178 for WT and trk-gene knockout strains at mid- and late-log phases, respectively.
Mentions: The efficiencies in K+ uptake of the two strains during the mid- and late-log phases were determined by measuring the absolute uptake of 86Rb+ by the strains during these growth phases. The results are represented as the mean radioactive counts per minute (cpm) values ± SEM and are shown in Figure 1. During both growth phases, the 86Rb+-uptake efficiencies of the trk-gene knockout strain were higher than those of the WT strain. However, the K+-uptake efficiencies of both strains were reduced as the bacteria entered the late-log phase.

Bottom Line: In both strains, mRNA levels of the K(+)-uptake encoding genes were relatively low compared to those of the housekeeping gene, sigA, at the early- and mid-log phases, increasing during late-log.Increased gene expression coincided with decreased K(+) uptake in the context of a drop in extracellular pH and sustained high extracellular K(+) concentrations.Decreasing the pH resulted in reductions in both membrane potential and K(+) uptake in the setting of significant induction of genes encoding both K(+) transporters.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Faculty of Health Sciences, University of Pretoria, Pretoria 0001, South Africa.

ABSTRACT
Two potassium (K(+))-uptake systems, Trk and Kdp, are operative in Mycobacterium tuberculosis (Mtb), but the environmental factors triggering their expression have not been determined. The current study has evaluated the expression of these genes in the Mtb wild-type and a trk-gene knockout strain at various stages of logarithmic growth in relation to extracellular K(+) concentrations and pH. In both strains, mRNA levels of the K(+)-uptake encoding genes were relatively low compared to those of the housekeeping gene, sigA, at the early- and mid-log phases, increasing during late-log. Increased gene expression coincided with decreased K(+) uptake in the context of a drop in extracellular pH and sustained high extracellular K(+) concentrations. In an additional series of experiments, the pH of the growth medium was manipulated by the addition of 1N HCl/NaOH. Decreasing the pH resulted in reductions in both membrane potential and K(+) uptake in the setting of significant induction of genes encoding both K(+) transporters. These observations are consistent with induction of the genes encoding the active K(+) transporters of Mtb as a strategy to compensate for loss of membrane potential-driven uptake of K(+) at low extracellular pH. Induction of these genes may promote survival in the acidic environments of the intracellular vacuole and granuloma.

No MeSH data available.


Related in: MedlinePlus