Identification, cloning, and characterization of a multicomponent biphenyl dioxygenase from Sphingobium yanoikuyae B1

Sinéad M. Ní Chadhain, Elizabeth M. Moritz, Eungbin Kim, Gerben J. Zylstra

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Abstract

Sphingobium yanoikuyae B1 utilizes both polycyclic aromatic hydrocarbons (biphenyl, naphthalene, and phenanthrene) and monocyclic aromatic hydrocarbons (toluene, m- and p-xylene) as its sole source of carbon and energy for growth. The majority of the genes for these intertwined monocyclic and polycyclic aromatic pathways are grouped together on a 39 kb fragment of chromosomal DNA. However, this gene cluster is missing several genes encoding essential enzymatic steps in the aromatic degradation pathway, most notably the genes encoding the oxygenase component of the initial polycyclic aromatic hydrocarbon (PAH) dioxygenase. Transposon mutagenesis of strain B1 yielded a mutant blocked in the initial oxidation of PAHs. The transposon insertion point was sequenced and a partial gene sequence encoding an oxygenase component of a putative PAH dioxygenase identified. A cosmid clone from a genomic library of S. yanoikuyae B1 was identified which contains the complete putative PAH oxygenase gene sequence. Separate clones expressing the genes encoding the electron transport components (ferredoxin and reductase) and the PAH dioxygenase were constructed. Incubation of cells expressing the dioxygenase enzyme system with biphenyl or naphthalene resulted in production of the corresponding cis-dihydrodiol confirming PAH dioxygenase activity. This demonstrates that a single multicomponent dioxygenase enzyme is involved in the initial oxidation of both biphenyl and naphthalene in S. yanoikuyae B1.

Original languageEnglish
Pages (from-to)605-613
Number of pages9
JournalJournal of Industrial Microbiology and Biotechnology
Volume34
Issue number9
DOIs
Publication statusPublished - 2007 Sep 1

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All Science Journal Classification (ASJC) codes

  • Biotechnology
  • Bioengineering
  • Applied Microbiology and Biotechnology

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