The Effect of Exogenous N-Acylated-L-Homoserine Lactones on the Remediation of Chromium-Contaminated Soil by Shewanella purefaciens

Microbial remediation of chromium-contaminated soil through extracellular electron transfer is an economical and environmentally friendly strategy. Exogenous quorum sensing (QS) signaling molecules could facilitate the process of electron transport. However, it remains unclear whether regulating QS could enhance the microbial remediation effect. In this study, exogenous N-acylated-L-homoserine lactones (AHLs) were added for the remediation of Cr(VI)-contaminated soil by S. putrefaciens. Various AHLs such as C8-HSL, C10-HSL, 3OC8-HSL, 3OC10-HSL and 3OC12-HSL were detected in the remediation, with the concentrations of 5.91 ng/L, 1.09 ng/L, 4.10 ng/L, 2.29 ng/L and 24.51 ng/L. The addition of C10-HSL and 3OC12-HSL significantly promoted the Cr(VI) reduction rates by 11.25% and 9.20%. There were also various AHLs in the Cr(VI) reduction by indigenous microorganisms. The AHLs species measured and their concentrations were C8-HSL (5.05 ng/L), C10-HSL (3.27 ng/L), C12-HSL (0.11 ng/L), 3OC8-HSL (0.11 ng/L), 3OC10-HSL (0.05 ng/L), and 3OC12-HSL (2.92 ng/L). Relative to the untreated control, supplementation with C8-HSL, C12-HSL, and 3OC12-HSL produced significant enhancements in the Cr(VI) reduction rates by 4.10%, 3.05%, and 2.24%, respectively (p < 0.05). Comparing the effects of AHL on the remediation by S. putrefaciens and indigenous microorganisms, it could be found that C10-HSL enhanced the remediation effect by increasing the reduction rates of S. putrefaciens, and 3OC12-HSL enhanced the remediation effect by increasing the reduction rates of indigenous microorganisms. This study introduces a distinctive pathway for the promotion of the microbial remediation effect and contributes to further understanding the communication mechanism between exogenous and indigenous microorganisms.