Degradation of 1,4-dichlorobenzene by a Pseudomonas sp

Abstract

A Pseudomonas species able to degrade p-dichlorobenzene as the sole source of carbon and energy was isolated by selective enrichment from activated sludge. The organism also grew well on chlorobenzene and benzene. Washed cells released chloride in stoichiometric amounts from o-, m-, and p-dichlorobenzene, 2,5-dichlorophenol, 4-chlorophenol, 3-chlorocatechol, 4-chlorocatechol, and 3,6-dichlorocatechol. Initial steps in the pathway for p-dichlorobenzene degradation were determined by isolation of metabolites, simultaneous adaptation studies, and assay of enzymes in cell extracts. Results indicate that p-dichlorobenzene was initially converted by a dioxygenase to 3,6-dichloro-cis-1,2-dihydroxycyclohexa-3,5-diene, which was converted to 3,6-dichlorocatechol by an NAD+-dependent dehydrogenase. Ring cleavage of 3,6-dichlorocatechol was by a 1,2-oxygenase to form 2,5-dichloro-cis, cis-muconate. Enzymes for degradation of haloaromatic compounds were induced in cells grown on chlorobenzene or p-dichlorobenzene, but not in cells grown on benzene, succinate, or yeast extract. Enzymes of the ortho pathway induced in cells grown on benzene did not attack chlorobenzenes or chlorocatechols. * Corresponding author. the enzyme (21, 28). Chloride is eliminated by lactonization of chloromuconic acids and subsequent reactions to yield P-ketoadipic acid (27).

Response of Soil Microbial Biomass to 1,2-Dichlorobenzene Addition in the Presence of Plant Residues

“…The response of fluorescent pseudomonads to 1,2-dichlorobenzene was selected for particular attention in this study. A number of fluorescent pseudomonad isolates are capable of degrading chlorobenzenes [6,7], including 1,2-dichlorobenzene [7]. They represent a large component of soil bacterial community, often accounting for between 10 to 14% of culturable soil isolates [8][9][10].…”

Microbial degradation of chlorobenzene under oxygen‐limited conditions leads to accumulation of 3‐chlorocatechol

“…Productive aerobic degradation of chlorobenzene by bacterial isolates has been reported frequently [6,[15][16][17][18][19][20][21][22]. Essentially, the degradation pathway is initiated by a dioxygenase attack and subsequent ortho cleavage of the 3-chlorocatechol formed, followed by further breakdown reactions and chloride elimination [6,[15][16][17][18][19][20]23]. This pathway, specific to the degradation of chlorinated aromatics via chlorocatechol, is usually designated the modified ortho pathway [24].…”

Microbiological methods for the cleanup of soil and ground water contaminated with halogenated organic compounds

“…Indeed, even strains capable of metabolising halobenzenes may be inhibited at relatively low substrate concentrations due to solvent-induced damage to cell membranes. Degradation of mono-, di-and trichlorobenzenes can be performed under aerobic conditions by soil, ground water and waste water populations [7][8][9][10][11][12]. Conversion to the corresponding chlorocatechols followed by ring cleavage and dechlorination has been ascertained as the metabolic pathway in aerobic degradative isolates [9][10][11][12].…”

“…Degradation of mono-, di-and trichlorobenzenes can be performed under aerobic conditions by soil, ground water and waste water populations [7][8][9][10][11][12]. Conversion to the corresponding chlorocatechols followed by ring cleavage and dechlorination has been ascertained as the metabolic pathway in aerobic degradative isolates [9][10][11][12]. The more substituted molecules appear to be highly resistant to aerobic microbial attack, although there is evidence for the reductive dehalogenation of hexachlorobenzene under methanogenic conditions [13,14].…”