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http://dspace.mediu.edu.my:8181/xmlui/handle/10261/3507| Title: | Heterologous Expression and Identification of the Genes Involved in Anaerobic Degradation of 1,3-Dihydroxybenzene (Resorcinol) in Azoarcus anaerobius |
| Publisher: | American Society for Microbiology |
| Description: | Azoarcus anaerobius, a strictly anaerobic, gram-negative bacterium, utilizes resorcinol as a sole carbon and
energy source with nitrate as an electron acceptor. Previously, we showed that resorcinol degradation by this
bacterium is initiated by two oxidative steps, both catalyzed by membrane-associated enzymes that lead to the
formation of hydroxyhydroquinone (HHQ; 1,2,4-benzenetriol) and 2-hydroxy-1,4-benzoquinone (HBQ). This
study presents evidence for the further degradation of HBQ in cell extracts to form acetic and malic acids. To
identify the A. anaerobius genes required for anaerobic resorcinol catabolism, a cosmid library with genomic
DNA was constructed and transformed into the phylogenetically related species Thauera aromatica, which
cannot grow with resorcinol. By heterologous complementation, a transconjugant was identified that gained the
ability to metabolize resorcinol. Its cosmid, designated R , carries a 29.88-kb chromosomal DNA fragment
containing 22 putative genes. In cell extracts of T. aromatica transconjugants, resorcinol was degraded to HHQ,
HBQ, and acetate, suggesting that cosmid R carried all of the genes necessary for resorcinol degradation. On
the basis of the physiological characterization of T. aromatica transconjugants carrying transposon insertions
in different genes of cosmid R , eight open reading frames were found to be essential for resorcinol mineralization.
Resorcinol hydroxylase-encoding genes were assigned on the basis of sequence analysis and enzyme
assays with two mutants. Putative genes for hydroxyhydroquinone dehydrogenase and enzymes involved in ring
fission have also been proposed. This work provides the first example of the identification of genes involved in
the anaerobic degradation of aromatic compounds by heterologous expression of a cosmid library in a
phylogenetically related organism. This work was supported by the Deutsche Forschungsgemeinschaft, Bonn, Germany, and by research funds of the University of Constance. Work in Spain was financed by grant VEM2003-20075-CO2-01 from the Spanish Ministry of Science and Education. JIM-B work in Germany was partially supported by a Spanish-German exchange program (Acciones Integradas) of the Ministry of Science and Education. Peer reviewed |
| URI: | http://dspace.mediu.edu.my:8181/xmlui/handle/10261/3507 |
| Other Identifiers: | Journal of Bacteriology 189(10): 3824–3833 (2007) 1098-5530 http://hdl.handle.net/10261/3507 10.1128/JB.01729-06 |
| Appears in Collections: | Digital Csic |
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