Detection, isolation, and identification of cadmium-resistant bacteria based on PCR-DGGE.

This study focused on the screening of cadmium-resistant bacterial strains from Pb-Zn tailing. We investigated the diversity of microbial community inhabiting Dong-san-cha Pb-Zn tailing in Beijing, China, by polymerase chain reaction-denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene of bacterial strain, and found two dominant strains in the DGGE profile. Using special culture media, we isolated two strong cadmium-resistant bacterial strains. On the basis of morphological, physiological, and biochemical characteristics, BIOLOG, and 16S rDNA sequencing, the two strains were identified as Bacillus cereus and Enterobacter cloacae. Minimal inhibitory concentrations (MICs) of heavy metals for the bacteria were determined. E. cloacae showed higher MIC values for heavy metals and a larger range of antibiotic resistance than B. cereus.

[Isolation, molecular characterization and resistance mechanism study on a cadmium hyperresistant Bacillus cereus].

A Gram-positive, aerobic, motile, spore-forming bacterium was isolated from a Pb-Zn mine tailing at suburb of Beijing City. The bacterial strain isolated could resist cadmium efficiently and it was able to grow well on media plates containing 1 000 mg/L cadmium. The DNA G + C content were found to be 60%. Phylogenetic analysis of the 16S rRNA gene revealed that this isolate was a member of the genus Bacillus. Two growth curves about this strain were drawn on media with and without cadmium. This strain harbors a plasmid putatively bearing essential cadmium resistant genes as demonstrated by a plasmid elimination experiment. The results of this study indicate that this strain has a better potential for cadmium resistance compared to other reports. The physiological characterization of the isolates also indicates the possible application of this strain for bioremediation of sites contaminated with cadmium.