Isolation and characterisation of new Gram-negative and Gram-positive atrazine degrading bacteria from different French soils

The: capacity of 12 soils to degrade atrazine was studied in laboratory inc ubations using radiolabelled atrazine. Eight soils showed enhanced degradat ion of this compound. Twenty-five bacterial strains able to degrade atrazin e were isolated by an enrichment method from 10 of these soils. These soils were chosen for their wide range of physico-chemical characteristics. Thei r history of treatment with atrazine was also variable. The genetic diversi ty of atrazine degraders was determined by amplified ribosomal restriction analysis (ARDRA) of the 165 rDNA gene with three restriction endonucleases. The 25 bacterial strains were grouped into five ARDRA types. By sequencing and aligning the 165 rDNA genes, the isolates were shown to belong to the Gram-negative species Chelatobacter heintzii, Aminobacter aminovorans. Sten otrophomonas maltophilia and to the Gram-positive genus Arthrobacter crysta llopoietes. These species were not described previously as being capable of atrazine degradation. Most Gram-negative bacteria could mineralise C-14 ri ng labelled atrazine and carried the atzA, atzB, atzC and trzD genes. Gram- positive strains could convert atrazine to cyanuric acid and carried only t he atzB and atzC genes. In this study, we describe the atrazine degradation capacities and corresponding genes in bacterial species that were not know n as atrazine degraders. We report for the first time the occurrence of the trzD gene in these atrazine-mineralising bacteria and we demonstrate the p otential use of colony hybridisation to isolate bacteria involved in atrazi ne degradation. (C) 2001 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.