engleski

Biotransformation activity of atrazine-degrading bacteria originating from industrial wastewater and soil

The objective of this study was to evaluate biotransformation activity of atrazine-degrading bacteria originating from an agrochemical factory wastewater and soil exposed to long-term pollution by atrazine production. The enrichment of atrazine- degrading bacteria was carried out in microcosms in mineral salts medium with atrazine as the only carbon and nitrogen source (AMS) and in the same medium with the addition of citrate as a supplemental carbon source. Five mixed cultures (two enriched from wastewater, and three from soils taken from top layer at different locations within the factory) were selected as the most efficient since they showed complete disappearance of atrazine (initial concentration 30 mgl-1) during 1- or 2- day batch cultivation in shaken flasks (monitored by HPLC analyses). A more detailed study of the mechanism of atrazine transformation suggested that all selected cultures expressed atrazine-mineralizing activity (transient metabolites hydroxyatrazine and cyanuric acid were monitored by HPLC analyses). It was also shown that the mixed cultures enriched from soil in the presence of citrate were more efficient in complete atrazine degradation than those enriched from wastewater in AMS medim with atrazine as the only carbon and nitrogen source. Plating on selective atrazine-agar medium demonstrated that all enrichments contained at least one bacterial strain which formed clear halos around the colonies. All these strains were capable of transforming atrazine to cyanuric acid, but none of them could continue degradation, i.e. the cleavage of s-triazine ring. Enrichment of mixed bacterial cultures which were more efficient in atrazine degradation than any of the individual populations alone suggested that the relationships between culture members, including those based on combined metabolic capability and the transfer of catabolic genes, are important for successful atrazine mineralization.

atrazine; biodegradation; atz genes

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