Enhanced atrazine removal by hydrophyte-bacterium associations and in vitro screening of the isolates for their plant growth-promoting potential

Emergent hydrophytes Acorus calamus, Typha latifolia, and Phragmites karka and epiphytic root bacteria isolated from their rhizoplanes were exposed to atrazine (5 and 10 mg l(-1)) individually and in plant-bacterium combination for 15 days hydroponically. It was observed that A. calamus-Pseudomonas sp. strain, the ACB combination, was best in decontamination, showing 91% and 87% removal of 5 and 10 mg l(-1) atrazine. Plant-bacterium association led to significant increase in atrazine decontamination as compared to decontamination by either plant or bacterium alone, indicating a synergistic action of the hydrophytes and isolates which led to enhanced atrazine removal. To the best of our knowledge this is the first report on the potential of plant-bacterium combinations for atrazine decontamination. The isolates showed augmented growth in the presence of plants and were able to alleviate atrazine stress in them. These isolates exhibited plant growth-promoting traits such as auxin, siderophore, Poly(3-hydroxybutyric acid)/succinogycan, ammonia, catalase production and solubilization of inorganic phosphate in vitro. The use of plant-bacterium mutualistic symbiosis for atrazine mitigation is a relatively simple, inexpensive, and clean technique and this phytoremediation-rhizoremediation combination is suggested to be tried on field to establish their potential for clean-up of contaminated sites.