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Effect of overexpressing nhaA and nhaR on sodium tolerance and lactate production in Escherichia coli
BACKGROUND: Like other bacteria, Escherichia coli must carefully regulate the intracellular concentration of sodium ion (Na(+)). During the bacterial production of any organic acid, cations like Na(+) invariably accumulate during a process which must maintain a near neutral pH. In this study, the E....
Autores principales: | , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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BioMed Central
2013
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3599867/ https://www.ncbi.nlm.nih.gov/pubmed/23360655 http://dx.doi.org/10.1186/1754-1611-7-3 |
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author | Wu, Xianghao Altman, Ronni Eiteman, Mark A Altman, Elliot |
author_facet | Wu, Xianghao Altman, Ronni Eiteman, Mark A Altman, Elliot |
author_sort | Wu, Xianghao |
collection | PubMed |
description | BACKGROUND: Like other bacteria, Escherichia coli must carefully regulate the intracellular concentration of sodium ion (Na(+)). During the bacterial production of any organic acid, cations like Na(+) invariably accumulate during a process which must maintain a near neutral pH. In this study, the E. coli nhaA gene encoding the Na(+)/H(+) antiporter membrane protein and the nhaR gene encoding the NhaA regulatory protein were overexpressed in wild-type E. coli MG1655 and in MG1655 pflB (ALS1317) which lacks pyruvate formate lyase activity and thus accumulates lactate under anaerobic conditions. RESULTS: Expression of either the nhaA or nhaR gene on the high copy inducible expression vector pTrc99A caused a significant reduction in the growth rate of MG1655. No change in growth rate was observed for MG1655 or ALS1317 for Na(+) concentrations of 0.75–0.90 M when the medium copy pBR322 plasmid was used to overexpress the two genes. In a fed-batch process to produce the model acid lactate with NaOH addition for pH control, lactate accumulation ceased in MG1655, MG1655/pBR322, MG1655/pBR322-nhaR and MG1655/pBR322-nhaA when the concentration reached 55–58 g/L. In an identical process lactate accumulation in MG1655/pBR322-nhaAR did not terminate until the concentration reached over 70 g/L. CONCLUSIONS: Although overexpression the genes did not improve growth rate at high Na(+) concentrations, the overexpression of nhaA and nhaR together led to a 25% increase in lactate production. Thus, the observed (absence of) impact that these genetic modifications had on growth rate is a poor indicator of their effect on acid accumulation. The overexpression of nhaAR did not cause faster lactate production, but permitted the culture to continue accumulating lactate at 10% greater Na(+) concentration. |
format | Online Article Text |
id | pubmed-3599867 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2013 |
publisher | BioMed Central |
record_format | MEDLINE/PubMed |
spelling | pubmed-35998672013-03-17 Effect of overexpressing nhaA and nhaR on sodium tolerance and lactate production in Escherichia coli Wu, Xianghao Altman, Ronni Eiteman, Mark A Altman, Elliot J Biol Eng Research BACKGROUND: Like other bacteria, Escherichia coli must carefully regulate the intracellular concentration of sodium ion (Na(+)). During the bacterial production of any organic acid, cations like Na(+) invariably accumulate during a process which must maintain a near neutral pH. In this study, the E. coli nhaA gene encoding the Na(+)/H(+) antiporter membrane protein and the nhaR gene encoding the NhaA regulatory protein were overexpressed in wild-type E. coli MG1655 and in MG1655 pflB (ALS1317) which lacks pyruvate formate lyase activity and thus accumulates lactate under anaerobic conditions. RESULTS: Expression of either the nhaA or nhaR gene on the high copy inducible expression vector pTrc99A caused a significant reduction in the growth rate of MG1655. No change in growth rate was observed for MG1655 or ALS1317 for Na(+) concentrations of 0.75–0.90 M when the medium copy pBR322 plasmid was used to overexpress the two genes. In a fed-batch process to produce the model acid lactate with NaOH addition for pH control, lactate accumulation ceased in MG1655, MG1655/pBR322, MG1655/pBR322-nhaR and MG1655/pBR322-nhaA when the concentration reached 55–58 g/L. In an identical process lactate accumulation in MG1655/pBR322-nhaAR did not terminate until the concentration reached over 70 g/L. CONCLUSIONS: Although overexpression the genes did not improve growth rate at high Na(+) concentrations, the overexpression of nhaA and nhaR together led to a 25% increase in lactate production. Thus, the observed (absence of) impact that these genetic modifications had on growth rate is a poor indicator of their effect on acid accumulation. The overexpression of nhaAR did not cause faster lactate production, but permitted the culture to continue accumulating lactate at 10% greater Na(+) concentration. BioMed Central 2013-01-29 /pmc/articles/PMC3599867/ /pubmed/23360655 http://dx.doi.org/10.1186/1754-1611-7-3 Text en Copyright ©2013 Wu et al; licensee BioMed Central Ltd. http://creativecommons.org/licenses/by/2.0 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. |
spellingShingle | Research Wu, Xianghao Altman, Ronni Eiteman, Mark A Altman, Elliot Effect of overexpressing nhaA and nhaR on sodium tolerance and lactate production in Escherichia coli |
title | Effect of overexpressing nhaA and nhaR on sodium tolerance and lactate production in Escherichia coli |
title_full | Effect of overexpressing nhaA and nhaR on sodium tolerance and lactate production in Escherichia coli |
title_fullStr | Effect of overexpressing nhaA and nhaR on sodium tolerance and lactate production in Escherichia coli |
title_full_unstemmed | Effect of overexpressing nhaA and nhaR on sodium tolerance and lactate production in Escherichia coli |
title_short | Effect of overexpressing nhaA and nhaR on sodium tolerance and lactate production in Escherichia coli |
title_sort | effect of overexpressing nhaa and nhar on sodium tolerance and lactate production in escherichia coli |
topic | Research |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3599867/ https://www.ncbi.nlm.nih.gov/pubmed/23360655 http://dx.doi.org/10.1186/1754-1611-7-3 |
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