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Journal of Bacteriology, August 2004, p. 4894-4902, Vol. 186, No. 15
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.15.4894-4902.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.

A Novel p-Nitrophenol Degradation Gene Cluster from a Gram-Positive Bacterium, Rhodococcus opacus SAO101

Wataru Kitagawa, Nobutada Kimura,* and Yoichi Kamagata

Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8566, Japan

Received 7 March 2004/ Accepted 29 April 2004

p-Nitrophenol (4-NP) is recognized as an environmental contaminant; it is used primarily for manufacturing medicines and pesticides. To date, several 4-NP-degrading bacteria have been isolated; however, the genetic information remains very limited. In this study, a novel 4-NP degradation gene cluster from a gram-positive bacterium, Rhodococcus opacus SAO101, was identified and characterized. The deduced amino acid sequences of npcB, npcA, and npcC showed identity with phenol 2-hydroxylase component B (reductase, PheA2) of Geobacillus thermoglucosidasius A7 (32%), with 2,4,6-trichlorophenol monooxygenase (TcpA) of Ralstonia eutropha JMP134 (44%), and with hydroxyquinol 1,2-dioxygenase (ORF2) of Arthrobacter sp. strain BA-5-17 (76%), respectively. The npcB, npcA, and npcC genes were cloned into pET-17b to construct the respective expression vectors pETnpcB, pETnpcA, and pETnpcC. Conversion of 4-NP was observed when a mixture of crude cell extracts of Escherichia coli containing pETnpcB and pETnpcA was used in the experiment. The mixture converted 4-NP to hydroxyquinol and also converted 4-nitrocatechol (4-NCA) to hydroxyquinol. Furthermore, the crude cell extract of E. coli containing pETnpcC converted hydroxyquinol to maleylacetate. These results suggested that npcB and npcA encode the two-component 4-NP/4-NCA monooxygenase and that npcC encodes hydroxyquinol 1,2-dioxygenase. The npcA and npcC mutant strains, SDA1 and SDC1, completely lost the ability to grow on 4-NP as the sole carbon source. These results clearly indicated that the cloned npc genes play an essential role in 4-NP mineralization in R. opacus SAO101.


* Corresponding author. Mailing address: Institute for Biological Resources and Functions, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8566, Japan. Phone: 81-29-861-6591. Fax: 81-29-861-6587. E-mail: n-kimura{at}aist.go.jp.


Journal of Bacteriology, August 2004, p. 4894-4902, Vol. 186, No. 15
0021-9193/04/$08.00+0     DOI: 10.1128/JB.186.15.4894-4902.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.




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