Inhibition of atrazine degradation by cyanazine and exogenous nitrogen in bacterial isolate M91-3.
A variety of s-triazine herbicides and nitrogen fertilizers frequently occur as co-contaminants at pesticide manufacturing and distribution facilities. The degradation of atrazine and cyanazine by the bacterial isolate M91-3 was investigated in washed-cell suspensions and crude cellular extracts. Cyanazine competitively inhibited atrazine degradation. The maximum atrazine degradation rate (Vmax) was 41 times higher and the half-saturation constant for the inhibitor (Ki) was 1.3 times higher in the crude cellular extract than in the washed-cell suspension, suggesting that cellular uptake influenced degradation of the s-triazines. Cultures that had received prior exposure to atrazine and simazine exhibited comparable atrazine degradation rates, while cells exposed to cyanazine, propazine, ametryne, cyanuric acid, 2-hydroxyatrazine, biuret, and urea exhibited a lack of atrazine-degradative activity. Growth in the presence of exogenous inorganic nitrogen inhibited subsequent atrazine-degradative activity in washed-cell suspensions, suggesting that regulation of s-triazine and nitrogen metabolism are linked in this bacterial isolate. These findings have significant implications for the environmental fate of s-triazines in agricultural settings since these herbicides are frequently applied to soils receiving N fertilizers. Furthermore, these results suggest that bioremediation of s-triazine-contaminated sites (common at pesticide distribution facilities in the cornbelt) may be inhibited by the presence of N fertilizers that occur as co-contaminants.
Gebendinger
N
N
Department of Plant and Soil Sciences, University of Delaware, Newark 19717-1303, USA.
Radosevich
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M
D001280:Atrazine / Q000378:metabolism*; D001419:Bacteria / Q000254:growth & development / Q000378:metabolism*; D001673:Biodegradation, Environmental; D006540:Herbicides / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism / Q000494:pharmacology*; D013997:Time Factors; D014227:Triazines / Q000378:metabolism*
D006540:Herbicides; D014227:Triazines; D009584:Nitrogen; D001280:Atrazine; C007168:cyanazine