title: Isolation of a Gram-positive poly(3-hydroxybutyrate) (PHB)-degrading bacterium from compost, and cloning and characterization of a gene encoding PHB depolymerase of Bacillus megaterium N-18-25-9.
abstract: A Gram-positive poly(3-hydroxybutyrate) (PHB)-degrading bacterial strain was isolated from compost. This organism, identified as Bacillus megaterium N-18-25-9, produced a clearing zone on opaque NB-PHB agar, indicating the presence of extracellular PHB depolymerase. A PHB depolymerase gene, PhaZ(Bm), of B. megaterium N-18-25-9 was cloned and sequenced, and the recombinant gene product was purified from Escherichia coli. The N-terminal half region of PhaZ(Bm) shared significant homologies with a catalytic domain of other PHB depolymerases. Although the C-terminal half region of PhaZ(Bm) showed no significant similarity with those of other PHB depolymerases, that region was necessary for the PHB depolymerase activity. Therefore, this enzyme's domain structure is unique among extracellular PHB depolymerase domain structures. The addition of PHB to the medium led to a sixfold increase in PhaZ(Bm) mRNA, while the presence of glucose repressed PhaZ(Bm) expression. The maximum activity was observed at pH 9.0 at 65 degrees C.
authors.affiliation: Department of Applied Life Sciences, Niigata University of Pharmacy and Applied Life Sciences, Niigata, Japan. htakaku@niigatayakudai.jp
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Takaku
authors.forename: Ayumi
authors.initials: A
authors.lastname: Kimoto
authors.forename: Shoko
authors.initials: S
authors.lastname: Kodaira
authors.forename: Masayuki
authors.initials: M
authors.lastname: Nashimoto
authors.forename: Masamichi
authors.initials: M
authors.lastname: Takagi
mesh_terms: D000595:Amino Acid Sequence; D001410:Bacillus megaterium / Q000145:classification / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D002265:Carboxylic Ester Hydrolases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification; D015964:Gene Expression Regulation, Bacterial; D006885:Hydroxybutyrates / Q000378:metabolism*; D008969:Molecular Sequence Data; D011091:Polyesters / Q000378:metabolism*; D012987:Soil; D012988:Soil Microbiology; D000094122:Polyhydroxybutyrates
chemical_list: D002265:Carboxylic Ester Hydrolases; D004269:DNA, Bacterial; D006885:Hydroxybutyrates; D011091:Polyesters; D012987:Soil; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates; C022417:poly-beta-hydroxybutyrate depolymerase