Impact of energy metabolism pathways in promoting phytoremediation of cadmium contamination by Bacillus amyloliquefaciens Bam1

Remediation plants combined with plant growth promoting rhizobacteria (PGPR) is one of the most promising means of remediation of Cd-contaminated soils at present. One of the PGPR, named Bacillus amyloliquefaciens Bam1, possessed high Cd resistance. Herein, comparative transcriptome analysis of B. amyloliquefaciens Bam1 revealed that its main energy metabolism pathway was significantly down-regulated under Cd stress. The pivotal genes involved in the energy production pathway, such as TCA cycle and respiratory chain, were then selected to construct the energy production enhanced strains named as Bam1sdhA, Bam1fumC, and Bam1qoxD. The Cd resistance of the three recombinant strains increased significantly by producing more ATP and less ROS, allowing them to colonize Cd-contaminated soil better than the wild-type Bam1 strain. The better colonization of strain Bam1fumC improved the photosynthesis and growth of the remediation plant, tomatoes, under Cd stress significantly. Furthermore, the Cd concentration accumulated in tomatoes with the Cd + Bam1fumC treatment was 1.88 times that of the Cd + Bam1 treatment. As the energy production enhanced, Bam1fumC exhibited considerable potential for development as a bioaugmentation assistant in Cd-contaminated phytoremediation. This study also provided a novel strategy for addressing soil Cd pollution remediation.