Anaerobic degradation of p-ethylphenol by "Aromatoleum aromaticum" strain EbN1: pathway, regulation, and involved proteins.
The denitrifying "Aromatoleum aromaticum" strain EbN1 was demonstrated to utilize p-ethylphenol under anoxic conditions and was suggested to employ a degradation pathway which is reminiscent of known anaerobic ethylbenzene degradation in the same bacterium: initial hydroxylation of p-ethylphenol to 1-(4-hydroxyphenyl)-ethanol followed by dehydrogenation to p-hydroxyacetophenone. Possibly, subsequent carboxylation and thiolytic cleavage yield p-hydroxybenzoyl-coenzyme A (CoA), which is channeled into the central benzoyl-CoA pathway. Substrate-specific formation of three of the four proposed intermediates was confirmed by gas chromatographic-mass spectrometric analysis and also by applying deuterated p-ethylphenol. Proteins suggested to be involved in this degradation pathway are encoded in a single large operon-like structure ( approximately 15 kb). Among them are a p-cresol methylhydroxylase-like protein (PchCF), two predicted alcohol dehydrogenases (ChnA and EbA309), a biotin-dependent carboxylase (XccABC), and a thiolase (TioL). Proteomic analysis (two-dimensional difference gel electrophoresis) revealed their specific and coordinated upregulation in cells adapted to anaerobic growth with p-ethylphenol and p-hydroxyacetophenone (e.g., PchF up to 29-fold). Coregulated proteins of currently unknown function (e.g., EbA329) are possibly involved in p-ethylphenol- and p-hydroxyacetophenone-specific solvent stress responses and related to other aromatic solvent-induced proteins of strain EbN1.
Max Planck Institute for Marine Microbiology, Bremen, Germany.
Lars
L
Wöhlbrand
Heinz
H
Wilkes
Thomas
T
Halder
Ralf
R
Rabus
D000098:Acetophenones / Q000378:metabolism; D000426:Alcohol Dehydrogenase / Q000235:genetics; D000693:Anaerobiosis; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D003903:Deuterium / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D008401:Gas Chromatography-Mass Spectrometry; D020869:Gene Expression Profiling; D023061:Gene Order; D005798:Genes, Bacterial; D007553:Isotope Labeling; D053858:Metabolic Networks and Pathways / Q000235:genetics*; D006899:Mixed Function Oxygenases / Q000235:genetics; D015394:Molecular Structure; D009876:Operon; D010636:Phenols / Q000378:metabolism*; D010626:Phenylethyl Alcohol / Q000031:analogs & derivatives / Q000378:metabolism; D020543:Proteome / Q000032:analysis; D043362:Rhodocyclaceae / Q000737:chemistry / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D000098:Acetophenones; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D010636:Phenols; D020543:Proteome; C011867:4-hydroxyphenylethanol; C042291:4-ethylphenol; D003903:Deuterium; D006899:Mixed Function Oxygenases; D000426:Alcohol Dehydrogenase; C049502:4-cresol dehydrogenase (hydroxylating); C031335:4-hydroxyacetophenone; D010626:Phenylethyl Alcohol