环境地球化学国家重点实验室知识库

Polymetallic exposure causes complex toxicity to microorganisms. In thisstudy, we investigated the responses of Escherichia coli under co-existence of cadmium(Cd) and lead (Pb), primarily based on biochemical analysis and RNA sequencing. Cdcompletely inhibited bacterial growth at a concentration of 2.41 mmol/L, with itsremoval rate as low as <10%. In contrast, the Pb removal rate was >95% under equimolar sole Pb stress. In addition, the Raman analysis confirmed the loss of proteinsfor the bacterial cells. Under the co-existence of Cd and Pb, the Cd toxicity to E. coliwas alleviated. Meanwhile, the biosorption of Pb cations was more intense during thecompetitive sorption with Cd. Transmission electron microscopy images showed that afew cells were elongated during incubation, i.e., the average cellular length increasedfrom 1.535 ± 0.407 to 1.845 ± 0.620 µm. Moreover, NanoSIMS imaging showed thatthe intracellular distribution of Cd and Pb was coupled with sulfur. Genes regulatingsulfate transporter were also upregulated to promote sulfate assimilation. Then, thesubsequent production of biogenic sulfide and sulfur-containing amino acids wasenhanced. Although this strategy based on S enrichment could resist the polymetallicstress, not all related genes were induced to upregulate under sole Cd stress. Therefore,the S metabolism might remodel the microbial resistance to variable occurrence ofheavy metals. Furthermore, the competitive sorption (in contrast to sole Cd stress) couldprevent microbial cells from strong Cd toxicity.