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Arnold KW, and Kaspar CW. (1995) Starvation and stationaryphase- Induced acid tolerance in Escherichia coli O157: H7, Appl. Environ. Microbiol. 61: 2037-2039.

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Article

Adaptive Responses in the Metabolism of Escherichia coli in View of Gene Expressions under Aerobic and Micro-aerobic Condition

1Department of Genetic Engineering and Biotechnology, University of Chittagong, Chittagong-4331, Bangladesh

2Department of Medicine, Upozila Health Complex, Cox¡¯s Bazar, Chittagong, Bangladesh

3Department of Pharmacy, University of Science and Technology (USTC) Chittagong, Bangladesh

4Department of Pediatrics, Chittagong Medical College, Chittagong Bangladesh

5Director Training and Deputy Commandant, Armed forces Medical College, Kurmitola, Dhaka 1206, Bangladesh

6Department of Biochemistry and Molecular Biology, University of Chittagong, Chittagong-4331, Bangladesh


American Journal of Microbiological Research. 2019, Vol. 7 No. 3, 91-97
DOI: 10.12691/ajmr-7-3-4
Copyright © 2019 Science and Education Publishing

Cite this paper:
Farhana Nasrin, Dr. Abul Kalam Azad, Mohammad Rashedul Hasan, Dr. Md. Maruful Kader, Br. Gen. Md. Saidur Rahman, Chowdhury Mohammad Monirul Hasan. Adaptive Responses in the Metabolism of Escherichia coli in View of Gene Expressions under Aerobic and Micro-aerobic Condition. American Journal of Microbiological Research. 2019; 7(3):91-97. doi: 10.12691/ajmr-7-3-4.

Correspondence to: Chowdhury  Mohammad Monirul Hasan, Department of Biochemistry and Molecular Biology, University of Chittagong, Chittagong-4331, Bangladesh. Email: monirbiochem@cu.ac.bd

Abstract

The major aims of biology to understanding life at a systems level. Escherichia coli is a metabolically versatile bacterium able to respond to changes in environmental factors availability. The effect of pH downshift on fermentation characteristics was investigated in a continuous culture of Escherichia coli at aerobic and micro-aerobic conditions. Regardless of oxygen availability, higher levels of acetate were associated with lower biomass yields and lower glucose consumption rates at pH 5.5 as compared to the observations made at pH 7.0. Observed gene expressions indicated that the down- regulation of the glucose uptake rate corresponded to the down-regulation of ptsG gene expression which in turn was caused by the up-regulation of mlc gene under the positive control of Crp. In accordance with up-regulation of arcA gene expression at acidic conditions, the expressions of TCA cycle-related genes such as icdA and gltA, and the respiratory chain gene cyoA were down-regulated, whereas cydB gene expression was up-regulated. Decreased activity of the TCA cycle caused more acetate formation at lower pH levels. Under micro-aerobic condition, higher levels of formate and lactate were produced at lower pH due to up-regulation of pflA, yfiD and ldhA genes. Meanwhile, lower levels of ethanol were produced due to the down-regulation of adhE gene at lower pH, as compared to the observation at neutral pH. The combined effect of pH and temperature on gene expression was also investigated and observed that decreases in the specific glucose consumption rate were associated with increases in the specific acetate production rate. This type of information is useful for the production of recombinant proteins, bio-molecules, simultaneous saccharification and fermentation (SSF) and strain improvement.

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