title: Osmotic stress response in Acinetobacter baylyi: identification of a glycine-betaine biosynthesis pathway and regulation of osmoadaptive choline uptake and glycine-betaine synthesis through a choline-responsive BetI repressor.
abstract: Acinetobacter baylyi, a ubiquitous soil bacterium, can cope with high salinity by uptake of choline as precursor of the compatible solute glycine betaine. Here, we report on the identification of a choline dehydrogenase (BetA) and a glycine betaine aldehyde dehydrogenase (BetB) mediating the oxidation of choline to glycine betaine. The betAB genes were found to form an operon together with the potential transcriptional regulator betI. The transcription of the betIBA operon and the two recently identified choline transporters was upregulated in response to choline and choline plus salt. The finding that the osmo-independent transporter BetT1 undergoes a higher upregulation in response to choline alone than betT2 suggests that BetT1 does not primarily function in osmoadaptation. Electrophoretic mobility shift assays led to the conclusion that BetI mediates transcriptional regulation of both, the betIBA gene operon and the choline transporters. BetI was released from the DNA in response to choline which together with the transcriptional upregulation of the bet genes in the presence of choline suggests that BetI is a choline sensing transcriptional repressor.
authors.affiliation: Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt, Frankfurt am Main, Germany.
authors.forename: Anica
authors.initials: A
authors.lastname: Scholz
authors.affiliation: Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt, Frankfurt am Main, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Stahl
authors.affiliation: Genoscope, Institut de Génomique (CEA), Evry, France.
authors.forename: Veronique
authors.initials: V
authors.lastname: de Berardinis
authors.affiliation: Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt, Frankfurt am Main, Germany.
authors.forename: Volker
authors.initials: V
authors.lastname: Müller
authors.affiliation: Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt, Frankfurt am Main, Germany.
authors.forename: Beate
authors.initials: B
authors.lastname: Averhoff
mesh_terms: D000150:Acinetobacter / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001622:Betaine / Q000378:metabolism*; D053898:Biosynthetic Pathways / Q000235:genetics*; D002794:Choline / Q000378:metabolism*; D050545:Choline Dehydrogenase / Q000235:genetics / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D015964:Gene Expression Regulation, Bacterial; D050789:Glycine Dehydrogenase / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D009876:Operon; D064587:Osmoregulation; D010084:Oxidation-Reduction; D012097:Repressor Proteins / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D026901:Membrane Transport Proteins; D012097:Repressor Proteins; D001622:Betaine; D050545:Choline Dehydrogenase; D050789:Glycine Dehydrogenase; D002794:Choline