Influence of chlorobenzoates on the utilisation of chlorobiphenyls and chlorobenzoate mixtures by chlorobiphenyl/chlorobenzoate-mineralising hybrid bacterial strains

Abstract

Chlorobenzoates (CBA) arise as intermediates during the degradation of polychlorinated biphenyls (PCBs) and some chlorinated herbicides. Since PCBs were produced as complex mixtures, a range of mono-, di-, and possibly trichloro-substituted benzoates would be formed. Chlorobenzoate degradation has been proposed to be one of the rate-limiting steps in the overall PCB-degradation process. Three hybrid bacteria constructed to have the ability to completely mineralise 2-, 3-, or 4-monochlorobiphenyl respectively, have been studied to establish the range of mono- and diCBAs that can be utilised. The three strains were able to mineralise one or more of the following CBAs: 2-, 3-, and 4-monochlorobenzoate and 3,5-dichlorobenzoate. No utilisation of 2,3-, 2,5-, 2,6-, or 3,4-diCBA was observed, and only a low concentration (0.11 mM) of 2,4-diCBA was mineralised. When the strain with the widest substrate range (Burkholderia cepacia JHR22) was simultaneously supplied with two CBAs, one that it could utilise plus one that it was unable to utilise, inhibitory effects were observed. The utilisation of 2-CBA (2.5 mM) by this strain was inhibited by 2,3-CBA (200 microM) and 3,4-CBA (50 microM). Although 2,5-cba and 2,6-cba were not utilised as carbon sources by strain jhr22, they did not inhibit 2-cba utilisation at the concentrations studied, whereas 2,4-cba was co-metabolised with 2-cba. The utilisation of 2-, 3-, and 4-chlorobiphenyl by strain JHR22 was also inhibited by the presence of 2,3- or 3,4-diCBA. We conclude that the effect of the formation of toxic intermediates is an important consideration when designing remediation strategies.

Integration of Matrix-Assisted Laser Desorption Ionization–Time of Flight Mass Spectrometry and Molecular Cloning for the Identification and Functional Characterization of Mobile ortho -Halobenzoate Oxygenase Genes in Pseudomonas aeruginosa Strain JB2

“…The latter include the use of halobenzoates as herbicides and formation during microbial degradation of these compounds (24). Chlorobenzoates (CBas) are also intermediates produced during aerobic biodegradation of polychlorinated biphenyls (PCBs), and in this process CBa degradation is important as accumulation of metabolites produced from CBas (i.e., chlorocatechols and protoanemonin) may result in feedback inhibition and impede PCB biotransformation (1,7,8,25,48,49). Thus, optimization of CBa degradation by using inoculants or genetically engineered strains can improve the effectiveness of PCB bioremediation (5,16,26,29,31,(39)(40)(41).…”

Change in the Bacterial Community of Natural River Biofilm during Biodegradation of Aniline-Derived Compounds Determined by Denaturing Gradient Gel Electrophoresis

“…24) This phenomenon has been described during the biodegradation of polychlorinated biphenyls (PCBs), where microorganisms usually metabolize only one aromatic ring and accumulate the others as the corresponding chlorobenzoates. 25,26) …”

Degradation of chlorinated benzoic acid mixtures by plant–bacteria associations

“…Chlorinated benzoic acids are common contaminants and arise as byproducts of PCB or chlorinated herbicide degradation [7,8]. For example, Fava et al [9] observed increases in 2CBA and 2,5‐dichlorobenzoic acid (25diCBA) concentrations during PCB degradation in a bioreactor.…”

“…For example, Fava et al [9] observed increases in 2CBA and 2,5‐dichlorobenzoic acid (25diCBA) concentrations during PCB degradation in a bioreactor. Furthermore, PCB‐contaminated sites will contain mixtures of chlorinated benzoic acids as the PCB mixture present in commercial PCB formulations (e.g., Aroclor™ 1260) degrades [8]. The occurrence of contaminant mixtures may pose a problem in site remediation because one toxic component of the mixture may limit degradation of other contaminants.…”