Bacterial consortia from raw water and sludges from water potabilization plants are able to degrade atrazine

• Atrazine-degrading ability by bacteria from water potabilization plants.
• Stable bacterial consortia enriched in low atrazine concentrations.
• Similar molecular community structure and pathway in five stable consortia.
• Effect of alternative N sources in the atrazine-degrading ability.

Atrazine is one of the most persistent herbicides that contaminate watercourses. However, its biodegradation has been scarcely studied in aquatic ecosystems. The present work studies the potential of bacteria collected from freshwater and sludges of three water potabilization plants to degrade atrazine. Bacteria from all samples, rarely exposed to the herbicide, were able to degrade atrazine as the sole N source in microcosms assays. Five bacterial consortia that degraded consistently 1 or 25 mg L−1 of atrazine within 48 h were established. T-RFLP analysis showed that three ribotypes accounting for more than 50% of the bacterial communities were common to the five consortia and the complete set of atrazine-degrading genes trzN, atzB, atzC and trzD was detected on them. Two consortia from the same origin but incubated with different atrazine concentrations (SAC 1 and SAC 25) contain isolates affiliated to Sinorhizobium sp. and Pseudomonas citronellolis, but Arthrobacter uraefaciens and Achromobacter xylosoxidans were specific of SAC 1 and SAC 25, respectively. These two consortia degraded atrazine in the presence of nitrate and grew in cyanuric acid. This paper describes the great potential for atrazine degradation by bacteria present in aquatic environments which can be exploited to design bioremediation processes.