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Abstract

The aerobic cometabolism of ortho-substituted chlorobenzoates by Pseudomonas aeruginosa strain 142 growing on glucose-supplemented medium was analyzed. The strain, which can use 2-chlorobenzoate (2-CBA) and 2,4-dichlorobenzoate (2,4-DCBA) as sole carbon and energy sources, showed high rates of 2-CBA metabolism in glucose-fed cells. In contrast, 2,4-DCBA was metabolized only after extended incubation of the full grown culture and depletion of glucose. In addition to the ortho-dehalogenation (ohb142) genes encoding the alpha and beta subunits of the oxygenase component of a 2-halobenzoate dioxygenase, strain 142 harbours a closely related ohbABCDFG gene cluster previously identified in P. aeruginosa JB2 (ohbJB2). The genes for the chlorocatechol ortho-catabolic pathway were identified and sequenced in this strain, showing a near complete identity with the clcABD operon of the pAC27 plasmid. Relative quantification of mRNA by RT-PCR shows a preferential induction of ohb142 by 2-CBA, which is abolished in glucose-grown cultures. The alternate ohbJB2 and clc genes were expressed preferentially in 2,4-DCBA grown cultures. Only ohbJB2 appears to be expressed in the presence of the carbohydrate. Detection of chlorocatechol-1,2-dioxygenase activity in 2,4-DCBA plus glucose grown cultures suggests the presence of an alternate system for the ortho-cleavage of chlorobenzoates. The recruitment of elements from two halobenzoate dioxygenase systems with different induction patterns, together with a chlorocatechol degradative pathway not repressed by carbon catabolite, may allow P. aeruginosa 142 to cometabolize haloaromatics in carbohydrate grown cultures.

Cometabolic degradation of mono-chloro benzoic acids by Rhodococcus sp. R04 grown on organic carbon sources

“…In this study, biodegradation of 2-CBA or 4-CBA by strain R04 grown on MM medium was failure, although 3-CBA was shown to be transformed by resting cells (unpublished data). The inability to mineralize these compounds may be related to the lack of induction of key metabolic reactions, the appearance of non-metabolizable intermediates, or the lack of suitable systems for uptake (Corbella et al 2001). Our research focus on the degradation and dechlorination of 2-CBA and 4-CBA by aerobic PCB-degrading bacteria R04 grown on MM medium supplemented with organic carbon sources.…”

“…It is quite common that an organic compound is chosen as a growth substrate. Several examples of cometabolism have been reported when the medium contains an alternate carbon source which can serves as sources of carbon and energy to support cell growth and induce the metabolic pathway (Kohler et al 1988;Adriaens and Focht 1991b;Corbella et al 2001). Necessary co-substrates NADH or NADPH used in many aerobic cometabolic reactions may be regenerated when glucose is used for cometabolic degradation (Wang and Loh 1999).…”

“…R04 (Sun and Qian 2002;Yang et al 2004). Since glucose is known to facilitate degradation of some chlorinated pollutants (Loh and Wang 1998;Wang and Loh 1999;Corbella et al 2001) it was tested as the selected carbon source. Ethanol was also tested because of its potential use as PCB solvent in laboratory studies.…”

Policing Right-Wing Dictatorships: Some preliminary comparisons of Fascist Italy, Nazi Germany and Franco’s Spain

“…They had done their best to avoid direct conflict with the rebels and, after the rebellion had failed, had protected them from revenge attacks. Several had later been retired for alleged disloyalty to the Republic 93 . Little is known about the purging process that lower-ranking members of the Civil Guard, or members of other police forces, underwent.…”