title: Impact of different CO2/HCO3- levels on metabolism and regulation in Corynebacterium glutamicum.
abstract: We investigated the growth kinetics and transcriptional responses of Corynebacterium glutamicum in environments with low (pCO2<40 mbar) and high (pCO2 ≥ 300 mbar) CO2/HCO3(-) levels compared to standard conditions. When cultivated at high CO2/HCO3(-)-levels, C. glutamicum showed increased (63%) biomass to substrate yields during the initial growth phase. Other kinetic parameters such as growth rate (μ), specific glucose consumption rate (qS), and selected enzymatic activities of anaplerotic reactions, the pentose phosphate pathway and the tricarboxylic acid cycle were similar to standard conditions. However, microarray hybridization disclosed a complex transcriptional response involving 117 differentially expressed genes. Among those, 60 genes were assigned to the complete DtxR/RipA regulon controlling iron homeostasis in C. glutamicum. Impaired growth of a ΔdtxR mutant at high CO2/HCO3(-) levels validated the relevance of this master regulator to cope with excessive CO2/HCO3(-) availability. At low CO2/HCO3(-) levels, C. glutamicum grew in a bi-level manner with three distinct growth phases. Differential analyses revealed approximately doubled activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase accompanied by the formation of L-alanine and L-valine during the lowest μ occurring in mid-phase of the cultivation. DNA microarray analysis revealed more than 100 differentially expressed genes in growth phase II compared to phase I including almost all thiamin pyrophosphate (TPP) biosynthesis genes, which were significantly up regulated. Concluding, we hypothesize that C. glutamicum counteracts the lack of CO2/HCO3(-) by triggering TPP biosynthesis for increasing the activities of TPP-dependent enzymes involved in CO2 formation.
authors.affiliation: University of Stuttgart, Institute of Biochemical Engineering, Allmandring 31, 70569 Stuttgart, Germany. Electronic address: blombach@ibvt.uni-stuttgart.de.
authors.forename: Bastian
authors.initials: B
authors.lastname: Blombach
authors.forename: Jens
authors.initials: J
authors.lastname: Buchholz
authors.forename: Tobias
authors.initials: T
authors.lastname: Busche
authors.forename: Jörn
authors.initials: J
authors.lastname: Kalinowski
authors.forename: Ralf
authors.initials: R
authors.lastname: Takors
mesh_terms: D000409:Alanine / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D018533:Biomass; D002245:Carbon Dioxide / Q000378:metabolism*; D048230:Corynebacterium glutamicum / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004167:Diphtheria Toxin / Q000096:biosynthesis; D015964:Gene Expression Regulation, Bacterial; D005947:Glucose / Q000378:metabolism; D005954:Glucosephosphate Dehydrogenase / Q000235:genetics; D013831:Thiamine / Q000096:biosynthesis; D014633:Valine / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D004167:Diphtheria Toxin; C075586:DtxR protein, Corynebacterium diphtheriae; D002245:Carbon Dioxide; D005954:Glucosephosphate Dehydrogenase; D014633:Valine; D005947:Glucose; D000409:Alanine; D013831:Thiamine
keywords: CO(2)/HCO(3)(−); Corynebacterium glutamicum; Diphtheria toxin repressor DtxR; Dissolved carbon dioxide; Thiamin biosynthesis