Anaerobic degradation of toluene by a denitrifying bacterium

Abstract

A denitrifying bacterium, designated strain Ti, that grew with toluene as the sole source of carbon under anaerobic conditions was isolated. The type of agar used in solid media and the toxicity of toluene were determinative factors in the successful isolation of strain Ti. Greater than 50% of the toluene carbon was oxidized to C02, and 29% was assimilated into biomass. The oxidation of toluene to CO2 was stoichiometrically coupled to nitrate reduction and denitrification. Strain Ti was tolerant of and grew on 3 mM toluene after a lag phase. The rate of toluene degradation was 1.8 ,umol min-' liter-' (56 nmol min-' mg of protein-) in a cell suspension. Strain Ti was distinct from other bacteria that oxidize toluene anaerobically, but it may utilize a similar biochemical pathway of oxidation. In addition, o-xylene was transformed to a metabolite in the presence of toluene but did not serve as the sole source of carbon for growth of strain Ti. This transformation was dependent on the degradation of toluene.

A strictly anaerobic betaproteobacteriumGeorgfuchsia toluolicagen. nov., sp. nov. degrades aromatic compounds with Fe(III), Mn(IV) or nitrate as an electron acceptor

“…Likely, the concentration of 2.5 mM nitrite used in this study was too high; lower concentrations of nitrite were not tested. Nitrite toxicity has often been reported for toluene-degrading denitrifying bacteria (Dolfing et al, 1990;Evans et al, 1991;Schocher et al, 1991).…”

Anaerobic Metabolism of Aromatic Compounds

“…Methyl substituents of the aromatic ring are difficult to attack in the absence of molecular oxygen, which normally initiates degradation. Methylated aromatic compounds, that are readily degraded anaerobically include toluene (Vogel and Grbic-Galic, 1986;Wilson et al, 1986;Zeyer et al, 1986;Dolfing et al, 1990: Lovley andLonergan, 1990;Schocher et al, 1991 ;Rabus et al, 1993;Fries et al, 1994: Rueter et al, 1994 and the ortho, rnetu and para isomers of xylene (Zeyer et al, 1986;Evans et al, 1991Evans et al, , 1992Seyfried et al, 1994;Edwards and Grbic-Galic, 1994;Rueter et al, 1994;Haner et al, 1995) and of cresol (Lovley and Lonergan, 1990;Hopper et al, 1991 ;Rudolphi et al, 1991 ;Flyvbjerg et al, 1993;Bonting et al, 1995). At least two different pathways can be used for the first attack under anaerobic conditions.…”

Thauera and Azoarcus as functionally important genera in a denitrifying quinoline-removal bioreactor as revealed by microbial community structure comparison

“…A remarkable feature of the process of denitrification is that it is often associated with the decomposition of organic matter under anaerobic conditions (Zoh, 1999). Environmental scientists have used this characteristic to degrade certain highly complex compounds (van Schie & Young, 1998;Song et al, 2000;Khan, 2002;Probian et al, 2003;Shinoda, 2004), such as monocyclic alkylbenzenes (Evans, 1991;Heider, 1998), halobenzoate (Coschigano et al, 1994;Song et al, 2000), phenol (van Schie & Young, 1998) and some polycyclic aromatic hydrocarbons (PAHs) (Rockne, 2000). Quinoline is one of the main nitrogen-containing PAHs (NPAHs), a class comprising strong pollutants present in soils and waters.…”