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Title: BIODEGRADATION OF ATRAZINE UNDER DENITRIFYING CONDITIONS BY THE SOIL BACTERIUM M91-3

Author
item CRAWFORD, JENNIFER - UNIV OF ILLINOIS
item MULVANEY, RICHARD - UNIV OF ILLINOIS
item SIMS, GERALD
item RADOSEVICH, M - UNIV OF DELAWARE/NEWARK

Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/2/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: A bacterium, designated M91-3, is known to grow in pure culture, using the herbicide atrazine as a source of nitrogen. In the present study, growth of M91-3 on atrazine in the absence of oxygen (anaerobic conditions) was investigated. The organism was able to use atrazine as its sole source of carbon and nitrogen under anaerobic conditions. One step in the process of degrading atrazine involved formation of hydroxyatrazine, a common atrazine degradation product in the environment. The organism was also able to carry out denitrification (conversion of nitrate to nitrogen gas) while using atrazine under anaerobic conditions. Though previous studies had shown M91-3 could be used to stimulate atrazine degradation aerobic (oxygen-containing) environments, inoculation of anaerobic sediments with the organism did not result in increased degradation suggesting the organism has little promise for enhancing atrazine degradation in anaerobic environments. The results of this study reveal an anaerobic mechanism for atrazine degradation, and show that degradation of atrazine is possible under denitrifying conditions, which are common in soils, natural waters, and temporarily flooded areas. These findings will be useful in developing approaches for predicting the fate of atrazine under temporary flooding conditions, which occur frequently in some agricultural areas where atrazine is used.

Technical Abstract: Anaerobic biodegradation of atrazine by the bacterial isolate M91-3 (ATCC#55512) was characterized with respect to mineralization, metabolite formation, and denitrification. The ability of the isolate to enhance atrazine biodegradation in anaerobic sediment slurries was also investigated. The organism utilized atrazine as its sole source of carbon and nitrogen under anaerobic conditions in batch column systems. Results of HPLC and TLC radiochromatography demonstrated that anaerobic biotransformation of atrazine by microbial isolate M91-3 involved hydroxyatrazine formation. Ring cleavage was demonstrated by 14CO2 evolution. Denitrification was confirmed by detection of 15N2 in headspace samples of 15NO3-amended anaerobic liquid cultures. In aquatic sediments, mineralization of uniformly ring-labeled 14C-atrazine (UL-(ring-14C)atrazine) occurred in both M91-3-inoculated and uninoculated sediment. Inoculation of sediments with M91-3 did not significantly enhance anaerobic mineralization of atrazine as compared to uninoculated sediment, which suggests the presence of indigenous organisms capable of anaerobic atrazine biodegradation to at least as great an extent as is the atrazine-degradating bacterial isolate M91-3. Results of this study demonstrate that under anaerobic conditions, M91-3 is capable of denitrification-coupled metabolism of atrazine. Atrazine served as a sole C and N source for the isolate, which catalyzed both atrazine ring cleavage and hydroxyatrazine formation.