Oxidative dealkylation of five phenylurea herbicides by the fungus CunninghamellaechinulataThaxter

Microorganisms isolated from soil degrade phenylurea herbicides via two major pathways: (i) direct hydrolysis by an amidase leading to N,O-dimethylhydroxylamine, CO₂ and aniline¹ and (ii) N-dealkylation, which has been described as the first step in urea herbicide degradation by a variety of organisms including mammals, plants and microbial systems (for a review see reference 2).Until now no attempts have been made to investigate the mechanism of N-demethylation of substituted ureas in soil microorganisms, due to the instability of the N-hydroxymethyl intermediates. This reaction mechanism has only been described in detail in green plants^3–5. As among soil fungi Phycomycetes are known to demethylate phenylurea herbicides^6,7 this study has been made to identify intermediate hydroxymethyl compounds from urea herbicides, when incubated with the fungus $\text{Cunninghamella echinulata Thaxter}$.     

Environmental chemistry of PCB-replacement compounds - V - the metabolism of chloro-isopropylbiphenyls in fish,frogs, fungi and bacteria

The metabolism of 2,5-dichloro-4'-isopropylbiphenyl and 4-chloro-4'-isopropylbiphenyl, two model compounds for alkylated chlorobiphenyls (Chloroalkylenes), has been investigated in fish, frogs, fungi and mixed cultures of bacteria. Fish (Carassius auratus) and frogs (Rana aesculenta) show a very limited metabolism of these compounds. A pure strain of fungus (Cunninghamella echinulata Thaxter) metabolized 2,5-dichloro-4'-isopropylbiphenyl both by stepwise oxidation of the isopropyl group to 2,5-dichloro-4'-biphenylcarboxylic acid and by hydroxylation of the chlorine substituted phenyl ring. A mixed culture of aerobic bacteria from activated sludge shows extensive degradation of 4-chloro-4'-isopropylbiphenyl to p-chlorobenzoic acid via stepwise oxidation of the isopropyl group when using the compound as sole carbon source. However, in the presence of D-glucose as additional carbon source, no metabolism is observed.