title: Role of central metabolism in the osmoadaptation of the halophilic bacterium Chromohalobacter salexigens.
abstract: Bacterial osmoadaptation involves the cytoplasmic accumulation of compatible solutes to counteract extracellular osmolarity. The halophilic and highly halotolerant bacterium Chromohalobacter salexigens is able to grow up to 3 m NaCl in a minimal medium due to the de novo synthesis of ectoines. This is an osmoregulated pathway that burdens central metabolic routes by quantitatively drawing off TCA cycle intermediaries. Consequently, metabolism in C. salexigens has adapted to support this biosynthetic route. Metabolism of C. salexigens is more efficient at high salinity than at low salinity, as reflected by lower glucose consumption, lower metabolite overflow, and higher biomass yield. At low salinity, by-products (mainly gluconate, pyruvate, and acetate) accumulate extracellularly. Using [1-(13)C]-, [2-(13)C]-, [6-(13)C]-, and [U-(13)C6]glucose as carbon sources, we were able to determine the main central metabolic pathways involved in ectoines biosynthesis from glucose. C. salexigens uses the Entner-Doudoroff pathway rather than the standard glycolytic pathway for glucose catabolism, and anaplerotic activity is high to replenish the TCA cycle with the intermediaries withdrawn for ectoines biosynthesis. Metabolic flux ratios at low and high salinity were similar, revealing a certain metabolic rigidity, probably due to its specialization to support high biosynthetic fluxes and partially explaining why metabolic yields are so highly affected by salinity. This work represents an important contribution to the elucidation of specific metabolic adaptations in compatible solute-accumulating halophilic bacteria.
authors.affiliation: Departamento de Bioquímica y Biología Molecular B e Inmunología. Facultad de Química, Campus Regional de Excelencia Internacional "Campus Mare Nostrum," Universidad de Murcia, 30100 Murcia, Spain.
authors.forename: José M
authors.initials: JM
authors.lastname: Pastor
authors.forename: Vicente
authors.initials: V
authors.lastname: Bernal
authors.forename: Manuel
authors.initials: M
authors.lastname: Salvador
authors.forename: Montserrat
authors.initials: M
authors.lastname: Argandoña
authors.forename: Carmen
authors.initials: C
authors.lastname: Vargas
authors.forename: Laszlo
authors.initials: L
authors.lastname: Csonka
authors.forename: Angel
authors.initials: A
authors.lastname: Sevilla
authors.forename: José L
authors.initials: JL
authors.lastname: Iborra
authors.forename: Joaquín J
authors.initials: JJ
authors.lastname: Nieto
authors.forename: Manuel
authors.initials: M
authors.lastname: Cánovas
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000599:Amino Acids, Diamino / Q000096:biosynthesis; D001426:Bacterial Proteins / Q000235:genetics; D018533:Biomass; D050260:Carbohydrate Metabolism; D002264:Carboxylic Acids / Q000378:metabolism; D055353:Chromohalobacter / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D002952:Citric Acid Cycle; D019295:Computational Biology; D005947:Glucose / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D054712:Salinity; D055049:Salt Tolerance; D012965:Sodium Chloride / Q000378:metabolism; D013194:Staining and Labeling
chemical_list: D000596:Amino Acids; D000599:Amino Acids, Diamino; D001426:Bacterial Proteins; D002264:Carboxylic Acids; D012965:Sodium Chloride; C045628:ectoine; D005947:Glucose
keywords: Ectoines; Entner-Doudoroff; Halophilic Bacteria; Metabolic Tracers; Metabolism; Microbiology; Nuclear Magnetic Resonance; Overflow Metabolism; Pyruvate Carboxylase; Salt Adaptation