| Abstrakt: |
It is known that hydrocarbon degradation can be coupled to dissimilatory microbial Fe(III) reduction under anaerobic conditions. Of the phylogenetically diverse Fe(III)-reducing organisms isolated and characterized only the Geobacter species have been shown to be capable of hydrocarbon oxidation, and even then, these organisms could only utilize simple monoaromatic hydrocarbons such as toluene. Analysis of the Geobacter metallireducens genome suggests that the route of aromatic hydrocarbon degradation in Fe(III) reducing bacteria mimics that found in facultative anaerobes with a few exceptions. Similar to facultative anaerobes, parent aromatic hydrocarbons are converted through an upper pathway to benzoyl-CoA. However, benzoyl-CoA appears to be reduced to cyclohexa-1,5-dienecarboxy-CoA by a novel protein complex. This novel benzoyl-CoA reductase (BCR) is hypothesized to contain proteins that have similarities to those found in hydrogenases, heterodisulfide reductases, NADH: Ubiquinone oxidoreductases, aldehyde/ketone: ferredoxin oxidoreductases, and selenium-containing proteins. Unlike other organisms, the method of activation is not ATP dependant, and may occur by a novel process. Here we discuss possible methods of activation, along with a mechanism detailing the steps of benzoate dearomatization and differences in benzoyl-CoA reductases from G. metallireducens and Thauera aromatica, a well-characterized hydrocarbon-oxidizing facultative anaerobe. [ABSTRACT FROM AUTHOR] |
