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Keywords:

  • environmental;
  • genes;
  • resistance;
  • soil;
  • stress response

Abstract

Aim

Lanzhou reach of the Yellow River is contaminated by cadmium (Cd(II)). The aim of this study was to screen bacterial strains that is able to resist and absorb cadmium from soil sediment and elucidate the molecular mechanism.

Methods and Results

A strain named LZ-11 which can resist 1 mmol l−1 and absorb 0·3 mmol l−1 cadmium was isolated from a petrochemical wastewater discharge site. 16S rRNA gene sequencing data and Vitek phenotype results revealed that it was closely related to Enterococcus faecalis. Transmission electron microscopy images and energy dispersive X-ray analysis results showed that Cd(II) was absorbed both intracellularly and extracellularly. Blast results showed that Enterococcus faecalis genome owns cadA, ppx and dsbA which are proven to be involved in Cd(II) resistance and absorption. Quantitative real-time PCR data demonstrated that thesethree genes were upregulated 2–3 folds in LZ-11 under Cd(II) treatment.

Conclusions

We've isolated a strain named LZ-11 from Lanzhou reach of the Yellow River which can resist and absorb Cd(II). LZ-11 was closely related to Enterococcus faecalis. Genes encoding CadA, Ppx and DsbA were up-regulated under Cd(II) treatment. These genes might confer Cd(II) resistance and absorption in Enterococcus faecalis strain LZ-11.

Significance and Impact of the Study

Lanzhou reach of the Yellow River is contaminated by heavy metals. Microbial research and remediation is still scarce. LZ-11 is the first strain that is able to resist and absorb Cd(II) isolated from this area and might be a good candidate for future cadmium bioremediation.