engleski

Catabolic activity, structure and composition of an atrazine-degrading community

The goal of this work was to better characterize an atrazine-degrading bacterial community (designated as M3) which was enriched from an agrochemical factory soil exposed to long-term contamination by s-triazine compounds. M3 mineralized 70.9 3.0% of [14C-ring] atrazine and 56.6 1.9% of [14C-ethyl] atrazine within 4 days of batch cultivation in mineral salts medium containing atrazine as the only nitrogen source. Degradation activity of M3 community toward different chloro- and methylthio-substituted s-triazine compounds was demonstrated as well. RFLP analysis of the 16S rRNA clone library revealed high population diversity of the community and the analyzed cloned sequences clustered within the Proteobacteria, the Actinobacteria, Bacteroidetes and Firmicutes. Dominant RFLP families were related to Pseudomonas, Flavobacterium, Paenibacillus and Arthrobacter species. Plate cultivation analysis showed that M3 community consisted of four culturable members possessing catabolic activities. Two of them, Arthrobacter sp. ATZ1 and Arthrobacter sp. ATZ2, are involved in the upper pathway and the other two, Ochrobactrum sp. CA1 and Pseudomonas sp. CA2, in the lower pathway of atrazine degradation]. PCR determination of the community atrazine-degrading genetic potential revealed the presence of the genes trzN, atzA, atzB, atzC and trzD. The genes trzN, atzB, atzC and insertion sequence related to IS1071 were found to be located on a single 190-kb plasmid in the community member ATZ2, while the gene trzD and IS1071 were detected on 355-kb plasmid in the members CA1 and CA2. The location of atzA remained unknown. The present study suggests that the enriched community represents a complex bacterial association expressing substantial atrazine-mineralizing activity and a broad specificity toward a range of s-triazine compounds. The study also suggests that, along with plasmid conjugation, IS could play a role in dispersing atrazine-catabolic genes within soil microbiota.

atrazin; bacterial community; diversity; trz; atz

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