Acetate Metabolism in <i>Escherichia coli</i> Strains Lacking Phosphoenolpyruvate: Carbohydrate Phosphotransferase System; Evidence of Carbon Recycling Strategies and Futile Cycles

Abstract

The ptsHIcrr operon was deleted from Escherichia coli wild-type JM101 to generate strain PB11 (PTS^–). In a mutant derived from PB11 that partially recovered its growth capacity on glucose by an adaptive evolution process (PB12, PTS^–Glc⁺), part of the phosphoenolpyruvate not used in glucose transport has been utilized for the synthesis of aromatic compounds. In this report, it is shown that on acetate as a carbon source, PB11 displayed a specific growth rate (μ) higher than PB12 (0.21 and 0.13 h^–1, respectively) while JM101 had a μ of 0.28 h^–1. To understand these growth differences on acetate, we compared the expression profiles of central metabolic genes by RT-PCR analysis. Obtained data revealed that some gluconeogenic genes were downregulated in both PTS^– strains as compared to JM101, while most glycolytic genes were upregulated in PB12 in contrast to PB11 and JM101. Furthermore, inactivation of gluconeogenic genes, like ppsA, sfcA, and maeB,and poxB gene that codes for pyruvate oxidase, has differential impacts in the acetate metabolism of these strains. Results indicate that growth differences on acetate in the PTS^– derivatives are due to potential carbon recycling strategies, mainly in PB11, and futile carbon cycles, especially in PB12.

New insights into Escherichia coli metabolism: carbon scavenging, acetate metabolism and carbon recycling responses during growth on glycerol

“…In these derivatives where the glycolytic metabolism is apparently functioning, the gluconeogenic metabolism is induced and glucose and acetate are utilized simultaneously [12,13,19,21,24]. These results indicate that growth on glycerol of strain JM101 could activate some important gluconeogenic genes like poxB and pckA involved in carbon (acetate) recycling.…”

Carbon sources-dependent carotenoid production in metabolically engineered Escherichia coli

“…The difference between the expected and obtained results may be due to the presence of more powerful factors controlling the flux towards carotenoid formation or catabolic repression network involved carbon sources(Gorke and Stulke 2008). Further investigation is underway using a PTS mutant E. coli strain as reported in the other studies(Balderas-Hernández et al 2009; Her- nandez-Montalvo et al 2003;Picon et al 2008;Sigala et al 2009) and through proteomic and metabolomic approaches. C40 cyclic b-carotene production (a) and HPLC analysis (b) of acetone extracts from recombinant E. coli [pACM-E BL -B BL -I BL -Y BL ] grown on glycerol: Peak 1 refers to b-carotene; peak 2 refers to dihydro-b-carotene…”

“…1). Using the altered physiological state, the production levels of metabolites of interest could be significantly enhanced (Hernandez-Montalvo et al 2003;Sigala et al 2009). …”

Global transcriptomic analysis of an engineered Escherichia coli strain lacking the phosphoenolpyruvate: carbohydrate phosphotransferase system during shikimic acid production in rich culture medium

“…Polyamines have also been associated with stabilizing membranes and stimulating several enzymes [17], and furthermore, spermidine was found to donate a portion of its molecule for the enzymatic biosynthesis of hypusine, a unique amino acid that plays a crucial role in cell proliferation [50]. Because strain PB12.SA22 ceased EXP growth by hour 9 of cultivation and entered a pseudo STA phase until the end of the fermentation, it is unlikely that arginine could be used as a polyamine precursor, suggesting that it could be used to supply succinate to TCA, through the gluconeogenic capabilities developed by strain PB12 [18,51], to make PEP available for use in SA production, particularly during the late STA phase in the absence of glucose (Figure  3). …”