Chemical and biological degradation of primary metabolites of atrazine by a Nocardia strain.

Abstract

The purpose of this paper is to elucidate the final degradative pathways of atrazine (I) by a Nocardia strain through experiments on the degradation of its metabolite, 4-amino-2-chloro-6isopropylamino-l ,3,5-triazine (Ha). This compound, in the bacterial medium, was transformed into several products identified as 2-chloro-4,6-diamino-l,3,5-triazine (lie), 4-amino-2-hydroxy-6isopropylamino-l ,3,5-triazine (VIII), 4-amino-l ,2-dihydro-l ,3,5-triazin-2-one (IV) and dicyanodiamidine (VII). The formation of (lie) was attributed to a microbial TV-dealkylation, while the detection of (IV) and (VII) was attributed to a chemical degradation of the intermediate 4-amino-2chloro-l,3,5-triazine (III). Compound (III) undergoes rapid hydrolysis and does not accumulate in the culture medium. Onthe basis of the microbial and chemical results, we propose a degradative pathway for atrazine. The study of transformation of "foreign chemicals" has increased in recent years because of the large amount of chemicals introduced in the environment. The transformations of pesticides in the environment may result from the activity of cellular or extracellular components of the biota (microorganisms, algae, higher plants and animals) as well as from chemical and photochemical reactions. It is very difficult to distinguish between these transformations, because all factors are often closely linked. Moreover, the properties of degradation products from pesticides are considerably different from

Fate of a Symmetric and an Asymmetric Triazine Herbicide in Silt Loam Soils

“…Chemical hydrolysis results in the formation of hydroxyatrazine (HA) (24-26). Microbial degradation results in N-dealkylation (27)(28)(29)(30) to form deethylatrazine (DEA), deisopropylatrazine (DIA), and deethyldeisopropylatrazine (DEDIA) (57). Further degradation of dealkylated products results in formation of 4-amino-2-chloro-l,3,5-triazine (52).…”

“…Further degradation of dealkylated products results in formation of 4-amino-2-chloro-l,3,5-triazine (52). Hydroxylation of dealkylated products or dealkylation of hydroxylated products results in the formation of deethylhydroxyatrazine (DEHA), deisopropylhydroxyatrazine (DIHA), and deethyldeisopropylhydroxyatrazine (DEDIHA) (28,29). Complete degradation of atrazine to C0 2 has been observed through continued hydroxylation of the triazine ring to form ammeline, ammelide, and cyanuric acid prior to ring cleavage (57).…”

In vitro evolution of an atrazine-degrading population under cyanuric acid selection pressure: Evidence for the selective loss of a 47kb region on the plasmid ADP1 containing the atzA, B and C genes

“…A number of studies have reported the isolation and the characterization of atrazinedegrading isolates (Behki et al, 1993;Bouquard et al, 1997;Devers et al, 2007aDevers et al, , 2007bGiardi et al, 1985;Mandelbaum et al, 1995;Rousseaux et al, 2001;Satsuma, 2006;Singh et al, 2004;Stamper et al, 2002;Strong et al, 2002;Struthers et al, 1998;Topp et al, 2000). Among the processes involved in the adaptation of the soil microflora to increasing atrazine degradation, horizontal gene transfer was shown to play a key role by favoring the exchange of the plasmid bearing the atz genes among the soil microflora (Devers et al, 2005).…”

Microbiological impact of atrazine pollution in river sediment and soil

“…The atrazine concentration decreased significantly, from 450 ng l -1 in Danube water to 50 ng l -1 in well water, though the total triazine concentration decreased only moderately (from 750 to 620 ng l -1 ). According to our current knowledge, the abiotic transformation of atrazine (for instance by photolytic hydrolysis; see below) yields only hydroxyatrazine; thus, the presence of dealkylated derivatives indicates the presence of endogenous atrazine-degrading microbial activity in the Danube sediment (Giardi et al, 1985).…”