Plant growth promoting rhizobacteria (PGPR) have a remediation effect on Cr-contaminated soil; however, the remediation scope is only within a small area around the bacteria. Hence, the remediation effect depends on the migration ability of bacteria in the soil. Root exudates enhance the chemotaxis and locomotion of Bacillus subtilis SL-44 by reducing its adhesion coefficient katt and hydrodynamic dispersion coefficient D. The locomotion capacity was enhanced by 7.84%–20.00%. Among the root exudates, proline and sucrose remarkably improved the motility of SL44. Biochar and bentonite increased the katt and D of SL-44, inhibited bacterial locomotion, and improved the retention rate on the carrier surface. Bacterial locomotion was reduced by biochar and bentonite by 57.99% and 50.42%, respectively. These reductions were caused by macropore. SL-44 locomotion was positively correlated with the concentration of environmental root exudate (R2 = 0.88−0.92). The results of the simulated soil study were validated in actual agricultural Cr-contaminated soils through qPCR.
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