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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) succinate dehydrogenase (SDH), (b) isocitrate dehydrogenase(ICD), (c) MDH (malate dehydrogenase), (d) glucose-6-phosphate dehydrogenase (G6PD) from External acidification of E. coli DH5 α for different time periods upon exposure to different low pH (acidic shock) using monensin as an uncoupler (1 μM). pH 7 was used as control (Mean ± SD for triplicate values)
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Figure 1: Comparison of specific activity of (a) succinate dehydrogenase (SDH), (b) isocitrate dehydrogenase(ICD), (c) MDH (malate dehydrogenase), (d) glucose-6-phosphate dehydrogenase (G6PD) from External acidification of E. coli DH5 α for different time periods upon exposure to different low pH (acidic shock) using monensin as an uncoupler (1 μM). pH 7 was used as control (Mean ± SD for triplicate values)

Mentions: When the external pH of E. coli cells in suspension was lowered from pH 7.5-5.5, the cytoplasmic pH fell within 10-20 s to pH 5.6-6.5. Rapid recovery occurred after 30 s of HCl addition and was followed by a slower recovery over the next 5 min. The pH of the periplasm equaled the external pH under all condition tested, including rapid acid shift. Addition of membrane permeant like sodium benzoate to the cell suspension has no effect on the periplasmic pH.[19] Uptake of a permeant acid can also dissipate the transmembrane pH, a component of the pmf. The permeant acids, such as sodium benzoate, can cross the bacterial membrane in the protonated and unprotonated forms and cyclically run down ΔpH, thereby collapsing pmf and uncoupling ATP synthesis.[20] The results show 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 used in the current study. On cytoplasmic acidification, the activities of all dehydrogenases decreased at pH 3, 4, and 5. On external acidification along with monensin [Figures 1 and 2], activities of dehydrogenases increased further as compared to external acidification alone. Cells exposed to pH 3 for 2 h had the highest acid tolerance on external acidification with or without monensin, which again supports the work of Tosun and Gonul. It was also found that activity of G6PD remained unchanged at low pH. This result suggested that, in a low pH environment, metabolic flux in E. coli increases through Tricarboxylic acid cycleTCA cycle and remains unaffected through the pentose phosphate pathway. This increase in metabolic flux through TCA cycle, during oxidative phosphorylation, cause electrons from NADH or FADH2 to pass onto O2 through the ETC located in the plasma membrane of the microorganism, leading to the pumping of protons out of the cytoplasm and thus maintaining pH homeostasis.


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) succinate dehydrogenase (SDH), (b) isocitrate dehydrogenase(ICD), (c) MDH (malate dehydrogenase), (d) glucose-6-phosphate dehydrogenase (G6PD) from External acidification of E. coli DH5 α for different time periods upon exposure to different low pH (acidic shock) using monensin as an uncoupler (1 μM). 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 1: Comparison of specific activity of (a) succinate dehydrogenase (SDH), (b) isocitrate dehydrogenase(ICD), (c) MDH (malate dehydrogenase), (d) glucose-6-phosphate dehydrogenase (G6PD) from External acidification of E. coli DH5 α for different time periods upon exposure to different low pH (acidic shock) using monensin as an uncoupler (1 μM). pH 7 was used as control (Mean ± SD for triplicate values)
Mentions: When the external pH of E. coli cells in suspension was lowered from pH 7.5-5.5, the cytoplasmic pH fell within 10-20 s to pH 5.6-6.5. Rapid recovery occurred after 30 s of HCl addition and was followed by a slower recovery over the next 5 min. The pH of the periplasm equaled the external pH under all condition tested, including rapid acid shift. Addition of membrane permeant like sodium benzoate to the cell suspension has no effect on the periplasmic pH.[19] Uptake of a permeant acid can also dissipate the transmembrane pH, a component of the pmf. The permeant acids, such as sodium benzoate, can cross the bacterial membrane in the protonated and unprotonated forms and cyclically run down ΔpH, thereby collapsing pmf and uncoupling ATP synthesis.[20] The results show 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 used in the current study. On cytoplasmic acidification, the activities of all dehydrogenases decreased at pH 3, 4, and 5. On external acidification along with monensin [Figures 1 and 2], activities of dehydrogenases increased further as compared to external acidification alone. Cells exposed to pH 3 for 2 h had the highest acid tolerance on external acidification with or without monensin, which again supports the work of Tosun and Gonul. It was also found that activity of G6PD remained unchanged at low pH. This result suggested that, in a low pH environment, metabolic flux in E. coli increases through Tricarboxylic acid cycleTCA cycle and remains unaffected through the pentose phosphate pathway. This increase in metabolic flux through TCA cycle, during oxidative phosphorylation, cause electrons from NADH or FADH2 to pass onto O2 through the ETC located in the plasma membrane of the microorganism, leading to the pumping of protons out of the cytoplasm and thus maintaining pH homeostasis.

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