Phytoremediation potential, antioxidant response, photosynthetic behavior and rhizosphere bacterial community adaptation of tobacco (Nicotiana tabacum L.) in a bisphenol A-contaminated soil

Bisphenol A (BPA) is an emerging organic pollutant, widely distributed and frequently detected in soil in recent years. BPA toxicity is a problem that needs to be solved in terms of both human health and agricultural production. Up to now, the toxic effect of BPA and its mechanism of action on plants, as well as the possibility of using plants to remediate BPA-contaminated soil, remain to be explored. In this study, six treatment groups were set up to evaluate the effects of different concentrations of BPA on the germination and growth of tobacco (Nicotiana tabacum L.) by medium experiments. Furthermore, the representative indexes of photosynthetic and antioxidant system were determined. Meanwhile, tobacco seedlings were cultivated in soil to further explore the effects of BPA on rhizosphere soil enzyme activity and bacterial community structure with or without 100 mg/kg BPA exposure. The enhancement of BPA removal efficiency from soil by phytoremediation using tobacco plants would also be estimated. Our results showed that high doses of BPA in solid medium remarkably inhibited tobacco seedling growth, and its toxicology effect was positively correlated with BPA concentration, while lower BPA exposure (< 20 mg/L) had little limitation on tobacco growth and induced hormesis effect, which was reflected mainly in the increase of root length. In pot experiments, the reducing of chlorophyll content (36.4%) and net photosynthetic rate (41.2%) meant the inhibition of tobacco photosynthetic process due to high concentration of BPA exposure (100 mg/kg) in soil. The increase of H2O2 and O-2(-) content suggested that BPA could destroy the balance of reactive oxygen species (ROS) in plants. However, tobacco plants still presented a high removal efficiency of BPA at the concentration of 100 mg/kg in soil, which could reach to 80% within 30 days. Furthermore, it was indicated that tobacco cultivation changed the structure of rhizosphere soil bacterial communities and the relative abundance of some valuable strains, including Proteobacteria, Acidobacteria and other strains, which might be participated in the BPA removal process. In addition, the tobacco-soil microbial system had the potential to reverse the negative effects caused by BPA through stimulating microorganism associated with soil nutrient cycling. In summary, tobacco is a competitive plant in phytoremediation of BPA-contaminated soil, though the growth of tobacco could be inhibited at high concentration of BPA. Moreover, tobacco might promote the removal efficiency of BPA by regulating the rhizosphere bacteria communities.