title: Transcriptional regulation and mutational analysis of a dctA gene encoding an organic acid transporter protein from Pseudomonas chlororaphis O6.
abstract: A dctA gene encoding a protein with identity to a C(4)-dicarboxylic acid/H(+) symporter was cloned from a beneficial root colonizer, Pseudomonas chlororaphis O6 (PcO6). Expression of the dctA gene was induced in minimal medium by several organic acids and was repressed by glucose. Highest expression was observed in early-logarithmic (log) cells grown on fumarate, acetate or succinate with decline as cells approached late-log growth phase. The dctA transcript accumulated weakly when cells were grown on malate, but strong expression was observed with benzoate. Expression of the dctA transcript was repressed in early-log cells upon addition of glucose to fumarate, but was detected as the cell culture aged. A dctA-deficient mutant of PcO6, constructed by marker exchange mutagenesis, did not grow on minimal medium containing succinate, benzoate, acetate or fumarate and growth on malate was delayed. The dctA mutant and wild-type grew equally on citrate, glucose, fructose, sucrose or inositol. We conclude that the transporter protein encoded by dctA is essential for utilization of certain organic acids and its expression is controlled by the availability of sugars.
authors.affiliation: Agricultural Plant Stress Research Center and Inst. of Agri. Sci. and Tech., College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, South Korea.
authors.forename: Hyo Song
authors.initials: HS
authors.lastname: Nam
authors.forename: Matt
authors.initials: M
authors.lastname: Spencer
authors.forename: Anne J
authors.initials: AJ
authors.lastname: Anderson
authors.forename: Baik Ho
authors.initials: BH
authors.lastname: Cho
authors.forename: Young Cheol
authors.initials: YC
authors.lastname: Kim
mesh_terms: D002241:Carbohydrates / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D029382:Dicarboxylic Acid Transporters / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008969:Molecular Sequence Data; D027501:Monocarboxylic Acid Transporters / Q000235:genetics*; D009154:Mutation; D010802:Phylogeny; D011549:Pseudomonas / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development; D012329:RNA, Bacterial / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic
chemical_list: D002241:Carbohydrates; D004269:DNA, Bacterial; D029382:Dicarboxylic Acid Transporters; D027501:Monocarboxylic Acid Transporters; D012329:RNA, Bacterial