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Applied and Environmental Microbiology, June 2009, p. 3912-3919, Vol. 75, No. 12
0099-2240/09/$08.00+0 doi:10.1128/AEM.01525-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
Phenol Degradation in the Strictly Anaerobic Iron-Reducing Bacterium Geobacter metallireducens GS-15
,
Kathleen M. Schleinitz,1*
Sirko Schmeling,4
Nico Jehmlich,2
Martin von Bergen,2
Hauke Harms,1
Sabine Kleinsteuber,1
Carsten Vogt,3 and
Georg Fuchs4
Department of Environmental Microbiology,1 Department of Proteomics,2 Department of Isotope Biogeochemistry, UFZ—Helmholtz Centre for Environmental Research, Leipzig, Germany,3 Mikrobiologie, Fakultät Biologie, Albert-Ludwigs-Universität, Freiburg, Germany4
Received 5 July 2008/ Accepted 8 April 2009
Information on anaerobic phenol metabolism by physiological groups of bacteria other than nitrate reducers is scarce. We investigated phenol degradation in the strictly anaerobic iron-reducing deltaproteobacterium Geobacter metallireducens GS-15 using metabolite, transcriptome, proteome, and enzyme analyses. The results showed that the initial steps of phenol degradation are accomplished by phenylphosphate synthase (encoded by pps genes) and phenylphosphate carboxylase (encoded by ppc genes) as known from Thauera aromatica, but they also revealed some distinct differences. The pps-ppc gene cluster identified in the genome is functional, as shown by transcription analysis. In contrast to T. aromatica, transcription of the pps- and ppc-like genes was induced not only during growth on phenol, but also during growth on benzoate. In contrast, proteins were detected only during growth on phenol, suggesting the existence of a posttranscriptional regulation mechanism for these initial steps. Phenylphosphate synthase and phenylphosphate carboxylase activities were detected in cell extracts. The carboxylase does not catalyze an isotope exchange reaction between 14CO2 and 4-hydroxybenzoate, which is characteristic of the T. aromatica enzyme. Whereas the enzyme of T. aromatica is encoded by ppcABCD, the pps-ppc gene cluster of G. metallireducens contains only a ppcB homologue. Nearby, but oriented in the opposite direction, is a ppcD homologue that is transcribed during growth on phenol. Genome analysis did not reveal obvious homologues of ppcA and ppcC, leaving open the question of whether these genes are dispensable for phenylphosphate carboxylase activity in G. metallireducens or are quite different from the Thauera counterparts and located elsewhere in the genome.
* Corresponding author. Mailing address: Helmholtz Centre for Environmental Research, Department of Environmental Microbiology, Permoserstr. 15, 04318 Leipzig, Germany. Phone: 49-341-235-1378. Fax: 49-341-235-1351. E-mail: kathleen.schleinitz{at}ufz.de
Published ahead of print on 17 April 2009.
Supplemental material for this article may be found at http://aem.asm.org/.
Applied and Environmental Microbiology, June 2009, p. 3912-3919, Vol. 75, No. 12
0099-2240/09/$08.00+0 doi:10.1128/AEM.01525-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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