PCR-DGGE and real-time PCR dsrB-based study of the impact of heavy metals on the diversity and abundance of sulfate-reducing bacteria

Sulfate-reducing bacteria (SRB) are widely used for heavy metal (HM) treatment in bioreactors but their growth and biological activity can be inhibited by such treatment. Here, bioreactor experiments were used to investigate changes in the SRB community and the copy number of the dissimilatory sulfite reductase β-subunit functional gene (dsrB) under high doses of sulfates and HMs. The SRB community was investigated using polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) and sequencing techniques, while the dsrB gene abundance was measured by quantitative real-time PCR (qRT-PCR). The sulfate reduction rate was initially much higher in reactors without HMs than in those containing HMs (p = 0.001). Sulfate levels were reduced by 50% within the first 3 days of operation. As a result, the HM removal rate was initially much lower in the reactors containing HMs. Most of the HMs reduced to safe limits within 9 ~ 12 days of operation. The SRB community mainly consisted of Desulfovibrio vulgaris, D. termitidis, D. desulfuricans, D. simplex and Desulfomicrobium baculatum, as determined by PCR-DGGE. qRT-PCR revealed a decreasing trend in the copy numbers of a functional gene (dsrB) after 6 days in samples lacking HMs; however, the opposite trend was observed in the HM-containing samples.