Bioaugmentation with Pseudomonas putida DOT-T1E is outweighed by natural microbial enrichment during bioremediation of organic atmospheric pollutants

Bioaugmentation with contaminant-degrading bacteria is a promising technology for the elimination of soil contaminants. However, this technology has not been deeply explored regarding atmospheric contaminants. Due to the health risks associated with indoor and outdoor pollutants in increasingly populated cities, mitigation of atmospheric contaminants is being recommended by many national and international environmental and health agencies. Mixtures of benzenes, toluene, xylenes and ethyl benzene (BTEX) are frequent and toxic atmospheric contaminants that affect humans and plants. Due to their toxicity, in many instances phytoremediation is not feasible. Here, we study the effects of a mixture of toluene, ethylbenzene, xylene (TEX) on plants either inoculated or not with the bacterium Pseudomonas putida DOT-T1E, which is tolerant and has the ability to mineralize some of the components of TEX. In our experiments, we demonstrated that the presence of this bacterium alleviated TEX toxicity toward clover plants and that the soil harbored activities involved in the elimination of these contaminants. Through metagenomic and metatranscriptomic analyses, we demonstrated that the presence of TEX increased the prevalence of Pseudomonas species and led to the overexpression of genes belonging to this genus associated with tolerance and degradation of aromatic compounds, regardless of bioaugmentation. Together, these results show that native soil microbiota are the primary drivers of TEX degradation.