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Evaluation on the responses of succinate dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase and glucose-6-phosphate dehydrogenase to acid shock generated acid tolerance in Escherichia coli.

Jain PK, Jain V, Singh AK, Chauhan A, Sinha S - Adv Biomed Res (2013)

Bottom Line: When challenged by low pH, protons enter the cytoplasm; as a result, mechanisms are required to alleviate the effects of lowered cytoplasmic pH.The activities of Succinate dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase and glucose-6-phosphate dehydrogenase in acid shocked cells of E. coli DH5 α and E. coli W3110 subjected to pH 3, 4, and 5 by two types of acidification, like external (using 0.1 N HCl), external along with the monensin (1 μM) and cytoplasmic acidification using the sodium benzoate as an acid permeant (20 mM) which is coupled to the electron transport chain by the reducing power, as yet another system possessed by E. coli as an armor against harsh acidic environments.Results showed that an exposure to acidic environment (pH 3, 4 and 5) for a short period of time increased the activities of these dehydrogenases in all types of acidification except cytoplasmic acidification, which shows that higher recycling of reducing power results in pumping out of protons from the cytoplasm through the electron transport chain complexes, thereby restoring the cytoplasmic pH of the bacteria in the range of 7.4-7.8.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Allen Career Institute, Kota, India.

ABSTRACT

Background: Escherichia coli have an optimum pH range of 6-7 for growth and survival that's why, called neutrophiles. The ΔpH across the cytoplasmic membrane is linked to cellular bioenergetics and metabolism of the body which is the major supplier of the proton motive force, so homeostasis of cellular pH is essential. When challenged by low pH, protons enter the cytoplasm; as a result, mechanisms are required to alleviate the effects of lowered cytoplasmic pH.

Materials and methods: The activities of Succinate dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase and glucose-6-phosphate dehydrogenase in acid shocked cells of E. coli DH5 α and E. coli W3110 subjected to pH 3, 4, and 5 by two types of acidification, like external (using 0.1 N HCl), external along with the monensin (1 μM) and cytoplasmic acidification using the sodium benzoate as an acid permeant (20 mM) which is coupled to the electron transport chain by the reducing power, as yet another system possessed by E. coli as an armor against harsh acidic environments.

Result: Results showed that an exposure to acidic environment (pH 3, 4 and 5) for a short period of time increased the activities of these dehydrogenases in all types of acidification except cytoplasmic acidification, which shows that higher recycling of reducing power results in pumping out of protons from the cytoplasm through the electron transport chain complexes, thereby restoring the cytoplasmic pH of the bacteria in the range of 7.4-7.8.

Conclusion: Study indicates that acid shocked E. coli for a period of 2 h can survive for a sustained period.

No MeSH data available.


Related in: MedlinePlus

Comparison of specific activity of (a) SDH, (b) ICD, (c) MDH, (d) G6PD from External acidification of E. coli W3110 for different time periods upon exposure to different low pH (acidic shock). pH 7 was used as control (Mean ± SD for triplicate values)
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Figure 4: Comparison of specific activity of (a) SDH, (b) ICD, (c) MDH, (d) G6PD from External acidification of E. coli W3110 for different time periods upon exposure to different low pH (acidic shock). pH 7 was used as control (Mean ± SD for triplicate values)

Mentions: The effect of a lowered extracellular pH on E. coli activates various pH homeostasis mechanisms, which restore the pH of the cytoplasm to near neutral. Pumping out protons from the cell is one of the many mechanisms that undo the effect of a lowered extracellular pH. Dehydrogenases when convert their substrate into its product, generate reducing power which on getting recycled at the ETC results in extrusion of protons out of the cell. In the present work, this expected result was confirmed by an increase in the specific activities of SDH, ICD and MDH on external acidification [Figures 3 and 4]. An increase in the specific activity suggests a higher flux of metabolites through the TCA cycle along with the recycling of the reducing power at the ETC. Moreover, the results in the present work are in accord with the work of Kannan et al. where these authors have, on a transcriptomic level, observed an up-regulation of succinate dehydrogenase on rapid external acidification of E. coli W3110.


Evaluation on the responses of succinate dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase and glucose-6-phosphate dehydrogenase to acid shock generated acid tolerance in Escherichia coli.

Jain PK, Jain V, Singh AK, Chauhan A, Sinha S - Adv Biomed Res (2013)

Comparison of specific activity of (a) SDH, (b) ICD, (c) MDH, (d) G6PD from External acidification of E. coli W3110 for different time periods upon exposure to different low pH (acidic shock). pH 7 was used as control (Mean ± SD for triplicate values)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3814565&req=5

Figure 4: Comparison of specific activity of (a) SDH, (b) ICD, (c) MDH, (d) G6PD from External acidification of E. coli W3110 for different time periods upon exposure to different low pH (acidic shock). pH 7 was used as control (Mean ± SD for triplicate values)
Mentions: The effect of a lowered extracellular pH on E. coli activates various pH homeostasis mechanisms, which restore the pH of the cytoplasm to near neutral. Pumping out protons from the cell is one of the many mechanisms that undo the effect of a lowered extracellular pH. Dehydrogenases when convert their substrate into its product, generate reducing power which on getting recycled at the ETC results in extrusion of protons out of the cell. In the present work, this expected result was confirmed by an increase in the specific activities of SDH, ICD and MDH on external acidification [Figures 3 and 4]. An increase in the specific activity suggests a higher flux of metabolites through the TCA cycle along with the recycling of the reducing power at the ETC. Moreover, the results in the present work are in accord with the work of Kannan et al. where these authors have, on a transcriptomic level, observed an up-regulation of succinate dehydrogenase on rapid external acidification of E. coli W3110.

Bottom Line: When challenged by low pH, protons enter the cytoplasm; as a result, mechanisms are required to alleviate the effects of lowered cytoplasmic pH.The activities of Succinate dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase and glucose-6-phosphate dehydrogenase in acid shocked cells of E. coli DH5 α and E. coli W3110 subjected to pH 3, 4, and 5 by two types of acidification, like external (using 0.1 N HCl), external along with the monensin (1 μM) and cytoplasmic acidification using the sodium benzoate as an acid permeant (20 mM) which is coupled to the electron transport chain by the reducing power, as yet another system possessed by E. coli as an armor against harsh acidic environments.Results showed that an exposure to acidic environment (pH 3, 4 and 5) for a short period of time increased the activities of these dehydrogenases in all types of acidification except cytoplasmic acidification, which shows that higher recycling of reducing power results in pumping out of protons from the cytoplasm through the electron transport chain complexes, thereby restoring the cytoplasmic pH of the bacteria in the range of 7.4-7.8.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Allen Career Institute, Kota, India.

ABSTRACT

Background: Escherichia coli have an optimum pH range of 6-7 for growth and survival that's why, called neutrophiles. The ΔpH across the cytoplasmic membrane is linked to cellular bioenergetics and metabolism of the body which is the major supplier of the proton motive force, so homeostasis of cellular pH is essential. When challenged by low pH, protons enter the cytoplasm; as a result, mechanisms are required to alleviate the effects of lowered cytoplasmic pH.

Materials and methods: The activities of Succinate dehydrogenase, isocitrate dehydrogenase, malate dehydrogenase and glucose-6-phosphate dehydrogenase in acid shocked cells of E. coli DH5 α and E. coli W3110 subjected to pH 3, 4, and 5 by two types of acidification, like external (using 0.1 N HCl), external along with the monensin (1 μM) and cytoplasmic acidification using the sodium benzoate as an acid permeant (20 mM) which is coupled to the electron transport chain by the reducing power, as yet another system possessed by E. coli as an armor against harsh acidic environments.

Result: Results showed that an exposure to acidic environment (pH 3, 4 and 5) for a short period of time increased the activities of these dehydrogenases in all types of acidification except cytoplasmic acidification, which shows that higher recycling of reducing power results in pumping out of protons from the cytoplasm through the electron transport chain complexes, thereby restoring the cytoplasmic pH of the bacteria in the range of 7.4-7.8.

Conclusion: Study indicates that acid shocked E. coli for a period of 2 h can survive for a sustained period.

No MeSH data available.


Related in: MedlinePlus