title: Cloning and expression of pyrroloquinoline quinone (PQQ) genes from a phosphate-solubilizing bacterium Enterobacter intermedium.
abstract: A grass rhizosphere bacterium, Enterobacter intermedium (60-2G), has a strong ability to solubilize insoluble phosphate. Certain phosphate-solubilizing bacteria secrete gluconic acid for this process. The gluconic acid is produced by direct extracellular oxidation of glucose by a glucose dehydrogenase equipped with pyrroloquinoline quinone (PQQ) as a cofactor. A pqq gene cluster producing PQQ was detected in E. intermedium and this sequence conferred phosphate-solubilizing activity to Escherichia coli DH5alpha. The 6,783-bp pqq sequence had six open reading frames (pqqA, B, C, D, E, and F) and showed 50-95% homology to pqq genes of other bacteria. E. coli DH5alpha expressing the E. intermedium pqq genes solubilized phosphate from hydroxyapatite after a pH drop to pH 4.0, which paralleled in time the secretion of gluconic acid. We speculate that production of PQQ in E. coli DH5alpha expressing the pqq cluster activates an endogenous glucose dehydrogenase to permit gluconic acid secretion that solubilizes the insoluble phosphate.
authors.affiliation: Division of Applied Plant Science, Agricultural Plant Stress Research Center, College of Agriculture and Life Sciences, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors.forename: Chul Hong
authors.initials: CH
authors.lastname: Kim
authors.forename: Song Hee
authors.initials: SH
authors.lastname: Han
authors.forename: Kil Yong
authors.initials: KY
authors.lastname: Kim
authors.forename: Baik Ho
authors.initials: BH
authors.lastname: Cho
authors.forename: Yong Hwan
authors.initials: YH
authors.lastname: Kim
authors.forename: Bon Sung
authors.initials: BS
authors.lastname: Koo
authors.forename: Young Cheol
authors.initials: YC
authors.lastname: Kim
mesh_terms: D003001:Cloning, Molecular; D003470:Culture Media / Q000737:chemistry; D015342:DNA Probes; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D017886:Durapatite / Q000378:metabolism; D004754:Enterobacter / Q000235:genetics* / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D023061:Gene Order; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D005942:Gluconates / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D045542:PQQ Cofactor / Q000096:biosynthesis* / Q000235:genetics*; D010710:Phosphates / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology; D012995:Solubility
chemical_list: D003470:Culture Media; D015342:DNA Probes; D004269:DNA, Bacterial; D005942:Gluconates; D010710:Phosphates; C008229:2-ketogluconate; D045542:PQQ Cofactor; D017886:Durapatite; C030691:gluconic acid