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Genetic evidence that the degradation of para-cresol by Geobacter metallireducens is catalyzed by the periplasmic para-cresol methylhydroxylase

  • Chaurasia, Akhilesh Kumar
  • Tremblay, Pier-Luc
  • Holmes, Dawn E.
  • Zhang, Tian
Publication Date
Jan 01, 2015
Online Research Database In Technology
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Two pathways for <i>para</i>-cresol (<i>p</i>-cresol) degradation by anaerobic bacteria have been elucidated; one involves fumarate addition at the methyl group of <i>p</i>-cresol by a hydroxylbenzylsuccinate synthase protein while the other utilizes a methylhydroxylase protein (PCMH) to catalyze hydroxylation of the methyl group of <i>p</i>-cresol. In <i>Geobacter metallireducens</i>, <i>in vitro</i> enzymatic assays showed that <i>p</i>-cresol is degraded via the methylhydroxylation pathway. However, prior to this study these results had not been confirmed by genetic analyses. In this work, the gene coding for benzylsuccinate-CoA dehydrogenase (<i>bbsG</i>), an enzyme required for toluene degradation by <i>G. metallireducens</i> that is homologous to the <i>p</i>-hydroxybenzylsuccinyl-CoA dehydrogenase involved in <i>p</i>-cresol degradation by <i>Desulfobacula toluolica</i> Tol2 via fumarate addition, and the gene encoding the alpha prime subunit of PCMH (<i>pcmI</i>), were deleted to investigate the possibility of co-existing p-cresol degradation pathways in G. metallireducens. The absence of a functional PcmI protein completely inhibited <i>p</i>-cresol degradation, while deletion of the <i>bbsG </i>gene had little impact. These results further support the observation that <i>G. metallireducens</i> utilizes a PCMH-initiated pathway for <i>p</i>-cresol degradation.

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