Thauera

A taxonomic note there have been substantial developments in the taxonomy of pseudomonads, and many new genera have been proposed including, for example, Sphingomonas, Comamonas, and Variovorax, while denitrifying organisms described as pseudomonads have been referred to the general Thauera and Azoarcus (Anders et al. 1995). 

Anders H-J, A Kaetzke, P Kampfer, W Ludwig, G Fuchs (1995) Taxonomic position of aromatic-degrading denitrifying pseudomonad strains K 172 and KB 740, and their description as new members of the genera Thauera, as Thauera aromatica sp. nov., and Azoarcus, as Azoarcus evansii sp. nov., respectively, members of the beta subclass of the Protobacteria. Int J Syst Bacterial 45 327-333. 

The degradation of alkyl benzenes (Hutchins 1991 Evans et al. 1991a,b Altenschmidt and Fuchs 1991). In these studies, some of the organisms referred to the genus Pseudomonas have been transferred to the genus Thauera (Anders et al. 1995). 

The mineralization of cholesterol by an organism related to Rhodocyclus, Thauera, and Azoarcus (Harder and Probian 1997). 

DeMoll-Decker H, JM Macy (1993) The periplasmic nitrite reductase of Thauera selenatis may catalyze the reduction of selenite to elementary selenium. Arch Microbiol 160 241-247. 

Macy JM, S Rech, G Auling, M Dorsch, E Stackebrandt, LI Sly (1993) Thauera selenatis gen. nov., sp. nov., a member of the beta subclass of Proteobacteria with a novel type of anaerobic respiration. Int J Syst Bacteriol 43 135-142. 

Schroder I, S Rech, T Krafft, JM Macey (1997) Purification and characterization of the selenate reductase from Thauera selenatis. J Biol Chem 272 23765-23768. 

There are several 2-ketoglutarate anaerobic oxidoreductases, for example, in Thauera aro-matica (Dorner and Boll 2002) and Azoarcus evansii (Ebenau-Jehle et al. 2003). Their role in the metabolism of arene carboxylates is discussed in Chapter 8, Part 3. 

The anaerobic degradation of some hydroxybenzoates and phenols involves reductive removal of the phenolic hydroxyl group. The enzyme that dehydroxylates 4-hydroxybenzoyl-CoA in Thauera aromatica is a molybdenum-flavin-iron-sulfur protein (Breese and Fuchs 1998), and is similar to the enzyme from the nonsulfur phototroph Rhodopseudomonas palustris that carries out the same reaction (Gibson et al. 1997). 

The selenate reductase from Enterobacter cloacae SLDla-1 functions only under aerobic conditions, and is not able to serve as an electron acceptor for anaerobic growth, in contrast to the periplasmic enzyme from Thauera selenatis (Schroder et al. 1997). In E. cloacae there are separate nitrate and selenate reductases, both of which are membrane-bound. The selenate reductase is able to reduce chlorate and bromate though not nitrate, contains Mo, heme and nonheme iron, and consists of three subunits in an a3p3y3 configuration. 

Breese K, G Fuchs (1998) 4-hydroxybenzoyl-CoA reductase (dehydroxylating) from the denitrifying bacterium Thauera aromatica prosthetic groups, electron donor, and genes of a member of the molybdenum-flavin-iron-sulfur proteins. Eur J Biochem 251 916-923. 

Dorner E, M Boll (2002) Properties of 2-oxoglutarate ferredoxin oxidoreductase from Thauera aromatica and its role in enzymatic reduction of the aromatic ring. J Bacterial 184 3975-3983. 

The chlorate reductase has been characterized in strain GR-1 where it was found in the periplasm, is oxygen-sensitive, and contains molybdenum, and both [3Fe-4S] and [4Fe-4S] clusters (Kengen et al. 1999). The arsenate reductase from Chrysiogenes arsenatis contains Mo, Fe, and acid-labile S (Krafft and Macy 1998), and the reductase from Thauera selenatis that is specific for selenate, is located in the periplasmic space, and contains Mo, Fe, acid-labile S, and cytochrome b (Schroeder et al. 1997). In contrast, the membrane-bound selenate reductase from Enterobacter cloacae SLDla-1 that cannot function as an electron acceptor under anaerobic conditions contains Mo and Fe and is distinct from nitrate reductase (Ridley et al. 2006). 

Thauera sp. strain DNT-1 is able to degrade toluene under aerobic conditions mediated by a dioxygenase, and under denitrifying conditions in the absence of oxygen by the anaerobic benzylsuccinate pathway (Shinoda et al. 2004). Whereas the tod genes were induced under aerobic conditions, the bss genes were induced under both aerobic and anaerobic conditions. 

Shinoda Y, Y Sakai, H Uenishi, Y Uchihashi, A Hiraishi, H Yukawa, H Yurimoto, N Kato (2004) Aerobic and anaerobic toluene degradation by a newly isolated denitrifying bacterium, Thauera sp. strain DNT-1. Appl Environ Microbiol 70 1385-1392. 

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). 

Leuthner B, C Leutwein, H Schulz, P Horth, W Haehnel, E Schiltz, H Schagger, J Heider (1998) Biochemical and genetic characterisation of benzylsuccinate synthase from Thauera aromatica a new glycyl-radical catalysing the first step in anaerobic toluene degradation. Mol Microbiol 28 515-628. 

Foss S, J Harder (1998) Thauera linaloolentis sp. nov. and Thauera terpenica sp. nov., isolated on oxygen-containing monoterpenes (linalool, menthol, and eucalyptol) and nitrate. System Appl Microbiol 21 365-373. 

Biegert T, G Fuchs (1995) Anaerobic oxidation of toluene (analogues) to benzoate (analogues) by whole cells and by cell extracts of a denitrifying Thauera sp. Arch Microbiol 163 407-417. 

Biegert T, G Fuchs, J Heider (1996) Evidence that anaerobic oxidation of toluene in the denitrifying bacterium Thauera aromatica is initiated by formation of benzylsuccinate from toluene and fumarate. Eur J Biochem 238 661-668. 

Biegert T, U Altenschmidt, C Eckerskorn, G Euchs (1995) Purification and properties of benzyl alcohol dehydrogenase from a denitrifying Thauera sp. Arch Microbiol 163 418-423. 

Breese K, M Boll, J Alt-Mdrbe, H Schaggrer, G Euchs (1998) Genes encoding the benzoyl-CoA pathways of anaerobic aromatic metabolism in the bacterium Thauera aromatica. Eur J Biochem 256 148-154. 

Schiihle K, G Fuchs (2004) Phenylphosphate carboxylase a new C-C lyase involved in anaerobic phenol metabolism in Thauera aromatica. J Bacterial 186 4556-4567. 

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. 

The anaerobic metabolism of L-phenylalanine by Thauera aromatica under denitrifying conditions involves several steps that result in the formation of benzoyl-CoA (a) conversion to the CoA-ester by a ligase, (b) transamination to phenylacetyl-CoA, (c) a-oxidation to phenylglyoxalate, and (d) decarboxylation to benzoyl-CoA (Schneider et al. 1997). 

Thauera sp. strain K172) (Dangel et al. 1991) and Rhodopseudomonas palustris (Egland et al. 1995). 

The fermentation of 3-hydroxybenzoate by Sporotomaculum hydroxybenzoicum produces acetate, butyrate, and CO2, with benzoate as a transient intermediate (Brauman et al. 1998). However, although the degradation of 3-hydroxybenzoate by Thauera aromatica begins with the formation of the CoA-ester, this is followed by the reduction of the ring with retention of the original hydroxyl group (Laempe et al. 2001). 

Heider J et al. (1998) Differential induction of enzymes involved in anaerobic metabolism of aromatic compounds in the denitrifying bacterium Thauera aromatica. Arch Microbiol 170 120-131. 

Laempe D, M Jahn, K Breese, H Schagger, G Euchs (2001) Anaerobic metabolism of 3-hydroxybenzoate by the denitrifying bacterium Thauera aromatica. J Bacteriol 183 968-979. 

Schneider S, G Fuchs (1998) Phenylacetyl-CoA acceptor oxidoreductase, a new a-oxidizing enzyme that produces phenylglyoxylate. Assay, membrane localization, and differential production in Thauera aro-matica. Arch Microbiol 169 509-516. 

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