Combined effects of sp. M6 strain and on rhizosphere community and bioremediation of cadmium polluted soils.

Concerns regarding inevitable soil translocation and bioaccumulation of cadmium (Cd) in plants have been escalating in concomitance with the posed phytotoxicity and threat to human health. Exhibiting a Cd tolerance, sp. M6 strain has been reported as a soil amendment owing to its capability of reducing metal bioavailability in soils. The present study investigated the rhizospheric bacterial community of the Cd hyperaccumulator using 16S gene sequencing. Additionally, the Cd removal efficiency of strain sp. M6 was enhanced by supplementing with biochar (C), glutamic acid (G), and rhamnolipid (R) to promote the phytoremediation effect of hyperaccumulator . To the best of our knowledge, this is the first time the amendments such as C, G, and R together with the plant-microbe system sp. M6 has been used for Cd bioremediation. The results showed that soil CaCl and DTPA (Diethylenetriamine penta-acetic acid) extractable Cd increased by 52.77 and 95.08%, respectively, in all M6 treatments compared to unamended control (CK). with sp. M6 supplemented with biochar and rhamnolipid displayed a higher phytoremediation effect, and the removal capability of soil Cd (II) reached up to 16.47%. Moreover, remediation of Cd polluted soil by sp. M6 also had an impact on the soil microbiome, including ammonia-oxidizing bacteria (AOB), ammonia-oxidizing archaea (AOA), and cadmium transporting ATPase ( genes. Quantitative PCR analysis confirmed the sp. M6 strain increased the abundance of AOB and in both low Cd (LC) and high Cd (HC) soils compared to AOA gene abundance. Besides, the abundance of and was found to be highest in both soils representing high tolerance capacity against Cd. While ranked third, indicating that the additionof strain could not make it the most dominant species. The results suggested the presence of the hyperaccumulator and Cd tolerant strain sp. M6 supplemented with biochar, and rhamnolipid, play a unique and essential role in the remediation process and reducing the bioavailability of Cd.