Open AccessIsolation 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
Author(s) -
Takaku Hiroaki,
Kimoto Ayumi,
Kodaira Shoko,
Nashimoto Masayuki,
Takagi Masamichi
Publication year - 2006
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2006.00448.x
Subject(s) - bacillus megaterium , escherichia coli , biochemistry , bacteria , biology , extracellular , cloning (programming) , microbiology and biotechnology , chemistry , gene , genetics , computer science , programming language
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°C.