Microbial breakdown of halogenated aromatic pesticides and related compounds

Abstract

Considerable progress has been made in the last few years in understanding the mechanisms of microbial degradation of halogenated aromatic compounds. Much is already known about the degradation mechanisms under aerobic conditions, and metabolism under anaerobiosis has lately received increasing attention. The removal of the halogen substituent is a key step in degradation of halogenated aromatics. This may occur as an initial step via reductive, hydrolytic or oxygenolytic mechanisms, or after cleavage of the aromatic ring at a later stage of metabolism. In addition to degradation, several biotransformation reactions, such as methylation and polymerization, may take place and produce more toxic or recalcitrant metabolites. Studies with pure bacterial and fungal cultures have given detailed information on the biodegradation pathways of several halogenated aromatic compounds. Several of the key enzymes have been purified or studied in cell extracts, and there is an increasing understanding of the organization and regulation of the genes involved in haloaromatic degradation. This review will focus on the biodegradation and biotransformation pathways that have been established for halogenated phenols, phenoxyalkanoic acids, benzoic acids, benzenes, anilines and structurally related halogenated aromatic pesticides. There is a growing interest in developing microbiological methods for clean‐up of soil and water contaminated with halogenated aromatic compounds.

Aerobic metabolism and adsorption of pyrethroid insecticide metofluthrin in soil

“…In the analogy of aerobic degradation of fluorobenzoic acids, 21) these metabolites are considered to be first dioxygenated to form the corresponding fluorocatechols which subsequently undergo ring cleavage and oxidation with liberation of fluoride.…”

Arthrobacter chlorophenolicus sp. nov., a new species capable of degrading high concentrations of 4-chlorophenol.

“…4-CP is a toxic and recalcitrant compound which is formed, for example, from chlorination of waste water, in pulp mills, from breakdown of herbicides such as 2,4-dichlorophenoxyacetic acid (Pritchard et al, 1987) and from anaerobic degradation of more highly chlorinated phenols, such as pentachlorophenol and 2,4,6-trichlorophenol (Madsen & Aamand, 1992 ;Woods et al, 1989). The toxicity of 4-CP is reflected in the fact that although several microbial strains can degrade 4-CP, such as certain members of the genera Pseudomonas, Alcaligenes and Arthrobacter (Ha$ ggblom, 1990(Ha$ ggblom, , 1992, degradation is usually limited to relatively low concentrations in the range of 20-100 p.p.m. (0n2-0n8 mM).…”

“…The black pigments were insoluble in water and formed a precipitate. The pigments could consist of accumulating intermediate(s) in the 4-CP degradation pathway (Ha$ ggblom, 1992). Further characterization of the pigments is under way.…”

Reductively debrominating strains of Propionigenium maris from burrows of bromophenol-producing marine infauna.

“…However, although mixed culture and J. Watson and others sediment slurry studies of marine haloaromatic dehalogenation and degradation are abundantly documented in the literature (e.g. Abrahamsson & Klick, 1991 ;Allard et al, 1991 ;Boothe et al, 1997 ;Genthner et al, 1989 ;Ha$ ggblom &Young, 1990King, 1988 ;Monserrate & Ha$ ggblom, 1997 ;Remberger et al, 1986) and dehalogenating bacteria from freshwater and terrestrial environments have been intensively studied (see El Fantroussi et al, 1998 ;Fetzner & Lingens, 1994 ;Ha$ ggblom, 1992 ;Hale et al, 1994 ;Janssen et al, 1994 ;Mohn & Tiedje, 1992 for recent reviews), marine strains highly active against multiply substituted haloaromatics have proven difficult to enrich and isolate into pure culture. This is particularly true of reductively dehalogenating organisms, which can remove halogen atoms from the aromatic ring.…”