title: Transcriptional analysis and adaptive evolution of Escherichia coli strains growing on acetate.
abstract: Eighteen strains of Escherichia coli were compared for maximum specific growth rate (μ MAX) on 85 mM acetate as the sole carbon source. The C strain ATCC8739 had the greatest growth rate (0.41 h(-1)) while SCS-1 had the slowest growth rate (0.15 h(-1)). Transcriptional analysis of three of the strains (ATCC8739, BL21, SMS-3-5) was conducted to elucidate why ATCC8739 had the greatest maximum growth rate. Seventy-one genes were upregulated 2-fold or greater in ATCC8739, while 128 genes were downregulated 2-fold or greater in ATCC8739 compared to BL21 and SMS-3-5. To generate a strain that could grow more quickly on acetate, ATCC8739 was cultured in a chemostat using a progressively increasing dilution rate. When the dilution rate reached 0.50 h(-1), three isolated colonies each grew faster than ATCC8739 on 85 mM acetate, with MEC136 growing the fastest with a growth rate of 0.51 h(-1), about 25 % greater than ATCC8739. Transcriptional analysis of MEC136 showed that eight genes were downregulated 2-fold or greater and one gene was upregulated 2-fold or greater compared to ATCC8739. Genomic sequencing revealed that MEC136 contained a single mutation, causing a serine to proline change in amino acid 266 of RpoA, the α subunit of the RNA polymerase core enzyme. The 260-270 amino acid region of RpoA has been shown to be a key region of the protein that affects the interaction of the α subunit of the RNA polymerase core enzyme with several global transcriptional activators, such as CRP and FNR.
authors.affiliation: BioChemical Engineering, College of Engineering, University of Georgia, Athens, GA, 30602, USA.
authors.forename: Eashwar
authors.initials: E
authors.lastname: Rajaraman
authors.forename: Ankit
authors.initials: A
authors.lastname: Agrawal
authors.affiliation: Department of Biology, Middle Tennessee State University, Murfreesboro, TN, 37132, USA.
authors.forename: Jacob
authors.initials: J
authors.lastname: Crigler
authors.affiliation: Department of Biology, Middle Tennessee State University, Murfreesboro, TN, 37132, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Seipelt-Thiemann
authors.affiliation: Department of Biology, Middle Tennessee State University, Murfreesboro, TN, 37132, USA.
authors.forename: Elliot
authors.initials: E
authors.lastname: Altman
authors.affiliation: BioChemical Engineering, College of Engineering, University of Georgia, Athens, GA, 30602, USA. eiteman@engr.uga.edu.|Department of Microbiology, University of Georgia, Athens, GA, 30602, USA. eiteman@engr.uga.edu.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Eiteman
mesh_terms: D000085:Acetates / Q000378:metabolism*; D000222:Adaptation, Physiological; D056804:Biofuels / Q000382:microbiology; D012321:DNA-Directed RNA Polymerases / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics*; D009154:Mutation
chemical_list: D000085:Acetates; D056804:Biofuels; D029968:Escherichia coli Proteins; D012321:DNA-Directed RNA Polymerases; C113275:RNA polymerase alpha subunit
keywords: Acetic acid; Adaptive evolution; Chemostat; Growth rate