MINERALIZATION OF THE S-TRIAZINE RING OF ATRAZINE BY STABLE BACTERIALMIXED CULTURES

Enrichment cultures containing atrazine loro-4-ethylamino-6-isopropyla mino-1,3,5-triazine) at a concentration of 100 ppm (0.46 mM) as a sole nitrogen source were obtained from soils exposed to repeated spills o f atrazine, alachlor, and metolachlor. Bacterial growth occurred conco mitantly with formation of metabolites from atrazine and subsequent bi osynthesis of protein. When ring-labeled [C-14]atrazine was used, 80% or more of the s-triazine ring carbon atoms were liberated as (CO2)-C- 14. Hydroxyatrazine may be an intermediate in the atrazine mineralizat ion pathway. More than 200 pure cultures isolated from the enrichment cultures failed to utilize atrazine as a nitrogen source. Mixing pure cultures restored atrazine-mineralizing activity. Repeated transfer of the mixed cultures led to increased rates of atrazine metabolism. The rate of atrazine degradation, even at the elevated concentrations use d, far exceeded the rates previously reported in soils, waters, and mi xed and pure cultures of bacteria.