Sorption and desorption of atrazine by three bacterial species isolated from aquatic systems

The isolates Acinetobacter spec., Cytophaga spec. and Pseudomonas fluorescens represent different morphological and physiological types of bacteria. They accumulate atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)-5-triazine) to different levels. Accumulation expressed by the ratio of atrazine sorbed per volume of bacteria to atrazine per the same volume of water amounted to 11 for Acinetobacter spec., 8.6 for Cytophaga spec. and 6.2 for Pseudomonas fluorescens. Accumulation ratios were proportional to the surface areas of the organisms. Single cells of Acinetobacter spec. sorbed amounts of atrazine comparable to the other species investigated, whereas cell aggregates, formed a few months after isolation, sorbed an order of magnitude less. A large portion of atrazine accumulated by the bacteria could be rapidly desorbed. A remainder of 10% was bound by Cytophaga spec. and Pseudomonas fluorescens. Acinetobacter spec. bound 70--80% of the atrazine sorbed. In the range of 0.3--3 mg/L atrazine, there was a linear relationship between the amount of non desorbable herbicide and its concentration in the incubation medium.