Screening of As-Resistant Bacterial Strains from the Bulk Soil and the Rhizosphere of Mycorrhizal Pteris vittata Cultivated in an Industrial Multi-Polluted Site

Arsenic (As) contamination poses significant environmental and health problems globally, especially in regions with high levels of exposure due to anthropogenic activities. Phytoremediation, particularly through the hyperaccumulator fern Pteris vittata, offers a promising approach to mitigate arsenic pollution. Bacteria and mycorrhizal fungi colonising the roots of P. vittata are involved in arsenic metabolism and resistance, and in promoting plant growth under stress conditions. A total of 45 bacterial strains were isolated from the soil and rhizosphere of P. vittata mycorrhizal fungi growing in an As-polluted industrial site. The bacteria were characterised for their plant beneficial characteristics, tolerance to sodium arsenate and arsenite, and for the presence of As-resistant genes. This study highlights the differences between the culturable fraction of the microbiota associated with the rhizosphere of P. vittata mycorrhizal plants and the bulk soil. In addition, several strains showing tolerance to arsenate up to 600 mM were isolated. All bacterial strains possessed arsC genes, and about 70% of them had arrA genes involved in the anaerobic arsenate respiration pathway. The possible exploitation of such bacterial strains in arsenic-assisted phytoremediation strategies highlights the importance of this study for developing new strategies for in situ phytoremediation.