Microbial aspects of atrazine biodegradation in relation to history of soil treatment

Abstract

Among 15 soils with different cropping practices, seven which had an history of repeated atrazine applications showed accelerated degradation of this herbicide. By contrast, grassland or agricultural soils with no recorded atrazine application, at least for the last three years, had a low degradation potential. No direct relation was found between the rate of atrazine mineralisation and the size of the microbial biomass. In adapted soils, the amounts of extractable residues were lowered and the very high percentages of radioactivity from [ring-14 C]atrazine recovered as [14 C]carbon dioxide demonstrated that N-dealkylation and deamidation were the only processes for micro-organisms to derive carbon and energy for heterotrophic growth. Kinetics of microbial 14 C accumulation revealed that atrazine ring carbon could be incorporated by direct oxidative condensation with structural components of the bacterial or fungal cell whereas side-chain carbon was preferentially used for biosynthesis of new protoplasmic cell material, as con®rmed by the high turnover rate of radiolabelled microbial components. From the determination of the Michaelis±Menten parameters, V m and K m in the presence of different selective biocides, it was possible to conclude that fungi were probably less active in atrazine degradation than bacteria and that over years the microbial atrazine-degrading community showed an increased ef®ciency.

Isolation and characterisation of new Gram-negative and Gram-positive atrazine degrading bacteria from different French soils

“…Our results are in agreement with observations described previously [18,19], except for the results of the soils of Le Rheu and Loustalet. In these other studies, the kinetics of atrazine degradation in soils was determined using 14 C ring labelled atrazine, in the present work we used 14 C ethyl chain labelled atrazine.…”

Bioaugmentation with Pseudomonas sp. strain MHP41 promotes simazine attenuation and bacterial community changes in agricultural soils

“…Microorganisms play an important role in the removal of persistent organic pollutants (POPs) from the environment (Philp et al, 2005). Natural microbial degradation of s-triazines has been reported in soils that have a history of s-triazine herbicide application (Ostrofsky et al, 1997;Yassir et al, 1999;Rousseaux et al, 2003;Morán et al, 2006). However, the decontamination of previously unexposed soils requires the enhancement of the natural degradation (Rousseaux et al, 2003).…”

Atrazine Degradation and Residues Distribution in Two Acid Soils from Temperate Humid Zone

“…In contrast, in G soil 33% of the applied atrazine was mineralized by week 2 and 49% by week 6, and then values remained fairly constant until the end of the experiment when a value of 53% was observed. These atrazine mineralization values were much higher than those obtained in soils with no atrazine application but were in the reported range given for soils with similar atrazine application history (Barriuso and Houot, 1996;Ostrofsky et al, 1997;Yassir et al, 1999;Abdelhafid et al, 2000aAbdelhafid et al, , 2000bHouot et al, 2000;Krutz et al, 2003). Variations in the number and activity of microorganisms growing at the expenses of atrazine and hence using the chemical as a source of carbon and energy (Ralebitso et al, 2002) are responsible for the kinetics of the herbicide dissipation in the two soils with previous annual herbicide treatment of 10 to 40 yr.…”