Transcriptome expression analysis of the gene regulation mechanism of bacterial mineralization tolerance to high concentrations of Cd.

Cadmium (Cd) pollution is a pressing environmental issue that must be addressed. In recent years, microbial mineralization biotechnology has been developed into an effective and eco-friendly heavy metal bioremediation solution. In the present research, RNA-Seq technology was utilized to reveal the molecular mechanism through which Bacillus velezensis LB002 induced the mineralization and Cd fixation under high-concentration Cd stress. The metabolic pathways involved in the genes that were significant differentially expressed in the process of bacterial mineralization were also investigated. The results showed that the physiological response of bacteria to Cd toxicity may include bacterial chemotaxis, siderophore complexation, and transport across cell membranes. Bacteria subjected to high-concentration Cd stress can up-regulate genes of argH, argF, hutU, hutH, lpdA, and acnA related to arginine synthesis, histidine metabolism, and citric acid cycle metabolism pathways, inducing vaterite formation and Cd fixation. Thus, the toxicity of Cd was decreased and bacteria were allowed to grow. Real-time quantitative polymerase chain reaction (RT-qPCR) results confirmed the data obtained by RNA-Seq, indicating that bacteria can reduce Cd toxicity by regulating the expression of related genes to induce mineralization. A basic bioremediation strategy to deal with high-concentration heavy-metal pollution was proposed from the perspective of gene regulation.