Assessing the efficiency and the side effects of atrazine-degrading biocomposites amended to contaminated soil

Even decades after being banned in Europe, atrazine can still be found in soils. Bioaugmentation with pesticide-degrading bacteria is a remediation technique that is already used experimentally to reclaim polluted soils. Its efficiency still needs to be improved and the use of carrier materials to deliver and stabilize pesticide-degrading microbes could be an interesting way to in situ investigations. Here, we produced atrazine-degrading biocomposites by bacterial biofilms either a single strain or a four-species consortium grown on zeolite as the carrier material. We evaluated their efficiency in mineralizing 14C-atrazine of agricultural soil versus free-living cells in a microcosm experiment. We also assessed the side effects of this bioremediation technology on the autochthonous soil microbial community. We showed that the atrazine mineralization potential of the free-living cells was higher than that of the biocomposites. However, soil microcosms inoculated with the biocomposites displayed significantly higher atrazine mineralization potential than the ones inoculated with free-living cells. Also, higher stability of the biocomposites after 15 and 34 days of incubation was confirmed by qPCR of the atrazine-degrading genes. The results of 16S rRNA amplicon sequencing indicated that the side effects of biocomposites on the autochthonous microbial diversity and composition are mild and depend on the atrazine substrate and zeolite. Altogether, our results provide the first evaluation of the efficiency and the ecotoxicological impacts of atrazine-degrading biocomposites in the soil.