Benzoate anaerobic degradation

Grbic-Galic, D. and L.Y. Young. 1985. Methane fermentation of ferulate and benzoate anaerobic degradation pathways. Appl. Environ. Microbiol. 50 292-297. 

Benzoyl-CoA reductase carries out the two-electron reduction of the aromatic ring dnring the anaerobic degradation of benzoate by Thauera aromatica. This involves two-electron transfer from ferredoxin, and a combination of EPR and Mossbaner spectroscopy showed the presence of three different clusters, while inactivation by oxygen was associated with partial conversion of [4Fe-4S] clnsters to [3Fe-4S] clnsters (Boll et al. 2000). 

Hartel U, E Eckel, J Koch, G Fuchs, D, Linder, W Buckel (1993) Purification of glutaryl-CoA dehydrogenase from Pseudomonas sp., an enzyme involved in the anaerobic degradation of benzoate. Arch Microbiol 159 174-181. 

Unusual reactions have been encountered in the aerobic degradations carried out by Azoarcus evan-sii and Geobacillus stearothermophilus (Zaar et al. 2001). The anaerobic degradation of benzoate by Azoarcus evansii (Ebenau-Jehle et al. 2003) and Thauera aromatica (Domer and Boll 2002), and of 3-hydroxybenzoate by Th. aromatica (Laempe et al. 2001) is discussed later. 

It has become clear that benzoate occupies a central position in the anaerobic degradation of both phenols and alkylated arenes such as toluene and xylenes, and that carboxylation, hydroxylation, and reductive dehydroxylation are important reactions for phenols that are discussed in Part 4 of this chapter. The simplest examples include alkylated benzenes, products from the carboxylation of napthalene and phenanthrene (Zhang and Young 1997), the decarboxylation of o-, m-, and p-phthalate under denitrifying conditions (Nozawa and Maruyama 1988), and the metabolism of phenols and anilines by carboxylation. Further illustrative examples include the following ... 

Anaerobic CP degradation involves sequential reductive dehalogenations with MCPs or DCPs as final metabolites, or degradation may proceed to complete dechlorination to phenol, further transformation to benzoate and, ultimately, conversion to methane and carbon dioxide. Reductive dechlorination of PCP, for example, results in the formation of meta- or para-CPs as the end-products (e.g., Woods et al., 1989 Madsen Aamand, 1992), or anaerobic degradation may continue to complete mineralization (Boyd Shelton, 1984 Mohn Kennedy, 1992 Wu et al., 1993). In reductive dechlorinations, CPs serve as electron acceptors and need a suitable electron donor. 

Shen, H., P.H. Pritchard, and G.W. Sewell. 1996. Microbial reduction of CrVI during anaerobic degradation of benzoate. Environ. Sci. Technol. 30 1667-1674. 

Decarboxylation is a key step in the degradation of glutarate to butyrate and isobutyrate by dehydrogenation to glutaconate followed by decarboxylation to crotonate (Matties and Schink 1992). This pathway has been proposed for the degradation of pimelate that is a possible intermediate in the anaerobic degradation of benzoate (Hartel et al. 1993 Gallus and Schink 1994). 

It seems clear that benzoate occupies a central position in the anaerobic degradation of both phenols and alkaryl hydrocarbons, and that carboxylation, hydroxylation, and reductive dehydroxylation are important—and less expected—reactions. 

Degradation of Benzoates—Benzoate occupies a central role in the metabolism of a range of aromatic compounds, and the pathway for its anaerobic degradation under denitrifying or phototrophic conditions involves three cardinal reactions (further references in Harwood et al. 1999) (Figure 6.94a,b) the designation of the enzymes corresponds to those for the genes discussed below. 

The degradation of o-, m-, and p-phthalates under denitrifying conditions has been examined (Nozawa and Maruyama 1988), and after an initial decarboxylation to benzoate followed the pathway for the anaerobic degradation of benzoate that has been noted above formation of the CoA ester, reduction to cyclohex-l-ene carboxylate, hydroxylation to 2-hydroxycyclohexane car-boxylate, and ring fission to pimelic acid that was further degraded by P-oxi-dation. 

Geissler, J.F., C.S. Harwood, and J. Gibson. 1988. Purification and properties of benzoate-coenzyme A ligase, a Rhodopseudomonas palustris enzyme involved in the anaerobic degradation of benzoate. /. Bacteriol. 170 1709-1714. 

Gibson, J., M. Dispensa, and C. S. Harwood. 1997. 4-Hydroxybenzoyl coenzyme A reductase dehydroxylating is required for anaerobic degradation of 4-hydrozy-benzoate by Rhodopseudomonas palustris and shares features with molybdenum-containing hydroxylases. J. Bacteriol. 179 634—642. 

Zhang, X. and J. Wiegel. 1992. The anaerobic degradation of 3-chloro4-hydroxyben-zoate in freshwater sediment proceeds via either chlorophenol or hydroxyben-zoate to phenol and subsequently to benzoate. Appl. Environ. Microbiol. 58 3580-3585. 

Figure 8 Reductive degradation pathways, (a) Anaerobic degradation of benzoate, (b) Reductive degradation of nitrobenzene by Pseudomonas pseudoalcaligenes JS45.

Energy yield of acetate oxidation with different electron acceptors is shown in Table 13.7. Also shown is energetics of aerobic and anaerobic degradation of benzoate with various electron acceptors found in wetland soils and sediments. Theses electron acceptors include O2, NO3, Fe, and SO ". 

Stable metabolic associations generally between pairs of anaerobic bacteria have been termed syntrophs, and these are effective in degrading a number of aliphatic carboxylic acids or benzoate under anaerobic conditions. These reactions have been discussed in reviews (Schink 1991, 1997 Lowe et al. 1993) that provide lucid accounts of the role of syntrophs in the degradation of complex organic matter. Two examples are given here to illustrate the experimental intricacy of the problems besetting the study of syntrophic metabolism under anaerobic conditions ... 

The degradation of Cg-benzene was studied in anaerobic enrichment cultures when phenol, benzoate, and toluene were detected, and the kinetics of their formation studied (Ulrich et al. 2005). 

Harrison EH, CS Harwood (2005) The pimEABCDE operon from Rhodopseudomonas palustris mediates dicarboxylic acid degradation and participates in anaerobic benzoate degradation. Microbiology (UK) 151 727-736. 

Egland PG, CS Harwood (1999) BadR, a new MarR family member regulates anaerobic benzoate degradation by Rhodopseudomonas palustris in concert with AadR, an Enr family member. J Bacteriol 181 2102-2109. 

Gibson KJ, J Gibson (1992) Potential early intermediates in anaerobic benzoate degradation by Rhodopseudomonas palustris. Appl Environ Microbiol 58 696-698. 

Pelletier DA, CS Harwood (1998) 2-ketohexanecarboxyl coenzyme A hydrolase, the ring cleavage enzyme required for anaerobic benzoate degradation by Rhodopseudomonas palustris. J Bacteriol 180 2330-2336. 

Knoll G, J. Winter (1989) Degradation of phenol via carboxylation to benzoate by a defined, obligate syn-trophic consortium of anaerobic bacteria. Appl. Microbiol. Biotechnol. 30 318-324. 

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