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Bioengineering 2017, 4(3), 61; doi:10.3390/bioengineering4030061

Insights on Osmotic Tolerance Mechanisms in Escherichia coli Gained from an rpoC Mutation

1
Department of Chemical Engineering, Texas A&M University, College Station, TX 77843, USA
2
Department of Chemical and Biological Engineering, University of Colorado-Boulder, Boulder, CO 80303, USA
Current address: Shell Biodomain, Houston, TX 77082, USA.
*
Author to whom correspondence should be addressed.
Academic Editor: Gou-Jen Wang
Received: 24 May 2017 / Revised: 22 June 2017 / Accepted: 24 June 2017 / Published: 28 June 2017
View Full-Text   |   Download PDF [4493 KB, uploaded 28 June 2017]   |  

Abstract

An 84 bp in-frame duplication (K370_A396dup) within the rpoC subunit of RNA polymerase was found in two independent mutants selected during an adaptive laboratory evolution experiment under osmotic stress in Escherichia coli, suggesting that this mutation confers improved osmotic tolerance. To determine the role this mutation in rpoC plays in osmotic tolerance, we reconstructed the mutation in BW25113, and found it to confer improved tolerance to hyperosmotic stress. Metabolite analysis, exogenous supplementation assays, and cell membrane damage analysis suggest that the mechanism of improved osmotic tolerance by this rpoC mutation may be related to the higher production of acetic acid and amino acids such as proline, and increased membrane integrity in the presence of NaCl stress in exponential phase cells. Transcriptional analysis led to the findings that the overexpression of methionine related genes metK and mmuP improves osmotic tolerance in BW25113. Furthermore, deletion of a stress related gene bolA was found to confer enhanced osmotic tolerance in BW25113 and MG1655. These findings expand our current understanding of osmotic tolerance in E. coli, and have the potential to expand the utilization of high saline feedstocks and water sources in microbial fermentation. View Full-Text
Keywords: E. coli; osmotic tolerance; rpoC; amino acid; acetic acid; membrane integrity; complex phenotype E. coli; osmotic tolerance; rpoC; amino acid; acetic acid; membrane integrity; complex phenotype
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MDPI and ACS Style

Guo, Y.; Winkler, J.; Kao, K.C. Insights on Osmotic Tolerance Mechanisms in Escherichia coli Gained from an rpoC Mutation. Bioengineering 2017, 4, 61.

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