Metabolism of both 4-chlorobenzoate and toluene under denitrifying conditions by a constructed bacterial strain

Abstract

T1, a dentrifying bacterium originally isolated for its ability to grow on toluene, can also metabolize 4-hydroxybenzoate and other aromatic compounds under denitrifying conditions. A cosmid clone carrying the three genes that code for the 4-chlorobenzoate dehalogenase enzyme complex isolated from the aerobic bacterium Pseudomonas sp. strain CBS3 was successfully conjugated into strain T1. The cloned enzyme complex catalyzes the hydrolytic dechlorination of 4-chlorobenzoate to 4-hydroxybenzoate. Since molecular oxygen is not required for the dehalogenation reaction, the transconjugate strain of T1 (T1-pUK45-10C) was able to grow on 4-chlorobenzoate in the absence of O2 under denitrifying conditions. 4-Chlorobenzoate was dehalogenated to 4-hydroxybenzoate, which was then further metabolized by strain T1. The dehalogenation and metabolism of 4-chlorobenzoate were nitrate dependent and were coupled to the production of nitrite and nitrogen gas. 4-Bromobenzoate was also degraded by this strain, while 4-iodobenzoate was not. Additionally, when T1-pUK45-10C was presented with a mixture of 4-chlorobenzoate and toluene, simultaneous degradation of the compounds was observed. These results illustrate that dechlorination and degradation of aromatic xenobiotics can be mediated by a pure culture in the absence of oxygen. Furthermore, it is possible to expand the range of xenobiotic substrates degradable by an organism, and it is possible that concurrent metabolism of these substrates can occur.

Anaerobic Biodegradation of Alkanes by Enriched Consortia Under Four Different Reducing Conditions

“…Iron(II) was determined by the FerroZine method as described by Kazumi et al [19]. Nitrate, nitrite, and sulfate were analyzed by ion chromatography as described by Coschigano et al [20]. Methane was analyzed by gas chromatographythermal conductivity detection as described by Phelps and Young [21].…”

Anaerobic degradation of benzene in BTX mixtures dependent on sulfate reduction

“…The amount of sulfate reduced during benzene degradation was compared to the amount predicted from the theoretical stoichiometric equation: CsH6+3.75SO;-+7SH+ +6C02+3.75HzS+3Hz0. Four active replicates were fed benzene alone repeatedly until they had consumed N 50 pmol, and then the amount of sulfate lost was measured using ion chromatography as previously described for nitrate and nitrite analysis [13]. The amount of sulfate reduced in duplicate background controls, which received no substrate, was subtracted from the result in order to account for sulfate loss due to metabolism of carbon compounds present in the sediment.…”

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.…”