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bph genes of the thermophilic PCB degrader, Bacillus sp. JF8: characterization of the divergent ring-hydroxylating dioxygenase and hydrolase genes upstream of the Mn-dependent BphC

Gouri Mukerjee-Dhar^1,

Daisuke Miyazawa^2,

Kazuhide Kimbara^1,2,

¹ Environmental Biotechnology Laboratory, Railway Technical Research Institute, Kokubunji, Tokyo 185-8540, Japan
² Department of Built Environment, Tokyo Institute of Technology, Yokohama 226-8502, Japan
³ Research Institute of Technology, Okayama University of Science, Okayama 703-8232, Japan

Correspondence
Minoru Shimura
mino{at}rtri.or.jp

Bacillus sp. JF8 is a thermophilic polychlorinated biphenyl (PCB) degrader, which utilizes biphenyl and naphthalene. A thermostable, Mn-dependent 2,3-dihydroxybiphenyl 1,2-dioxygenase, BphC_JF8, has been characterized previously. Upstream of bphC are five ORFs exhibiting low homology with, and a different gene order from, previously characterized bph genes. From the 5' to 3' direction the genes are: a putative regulatory gene (bphR), a hydrolase (bphD), the large and small subunits of a ring-hydroxylating dioxygenase (bphA1A2), and a cis-diol dehydrogenase (bphB). Hybridization studies indicate that the genes are located on a plasmid. Ring-hydroxylating activity of recombinant BphA1A2_JF8 towards biphenyl, PCB, naphthalene and benzene was observed in Escherichia coli cells, with complementation of non-specific ferredoxin and ferredoxin reductase by host cell proteins. PCB degradation by recombinant BphA1A2_JF8 showed that the congener specificity of the recombinant enzyme was similar to Bacillus sp. JF8. BphD_JF8, with an optimum temperature of 85 °C, exhibited a narrow substrate preference for 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid. The Arrhenius plot of BphD_JF8 was biphasic, with two characteristic energies of activation and a break point at 47 °C.

The GenBank/EMBL/DDBJ accession numbers for the sequences reported in this paper are AB113649 and AB181508.

A figure showing amino acid sequence comparisons is available as supplementary data with the online version of this paper.

Present address: Genetics and Genomic Biology Program, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M2G 1X8.

Present address: Department of Microbiology and Biochemistry, University of British Columbia, 300-6174 University Blvd, Vancouver, BC, Canada V6T 1Z3.

Present address: Research Institute for Bioresources, Okayama University, 2-20-1 Chuo, Kurashiki, Okayama 710-0046, Japan.

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