title: Acetate metabolism in Escherichia coli 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 (mu) higher than PB12 (0.21 and 0.13 h(-1), respectively) while JM101 had a mu 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.
authors.affiliation: Departamento de Ingeniería Celular y Biocatálisis, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca/Morelos, México.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Sigala
authors.forename: Salvador
authors.initials: S
authors.lastname: Flores
authors.forename: Noemí
authors.initials: N
authors.lastname: Flores
authors.forename: César
authors.initials: C
authors.lastname: Aguilar
authors.forename: Ramón
authors.initials: R
authors.lastname: de Anda
authors.forename: Guillermo
authors.initials: G
authors.lastname: Gosset
authors.forename: Francisco
authors.initials: F
authors.lastname: Bolívar
mesh_terms: D000085:Acetates / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D015971:Gene Expression Regulation, Enzymologic; D020868:Gene Silencing; D005798:Genes, Bacterial / Q000235:genetics; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015219:Substrate Cycling
chemical_list: D000085:Acetates; D010728:Phosphoenolpyruvate; D002244:Carbon; D010770:Phosphotransferases