Changes in rhizosphere bacterial populations during phytoextraction of heavy metal contaminated soil with poplar

摘要

The objective of this paper was to study the response of rhizosphere ammonia-oxidizing bacterial (AOB) populations during phytoextraction. Hybrid poplars were grown in compartmented root containers with an aged heavy metal (HM)-contaminated soil for 13 weeks. Bulk and poplar rhizosphere soils were analyzed by denaturing gradient gel electrophoresis (DGGE) of amoA gene fragments. DGGE patterns revealed that amoA-containing populations in the contaminated soils were markedly different from those in the uncontaminated soils. AmoA profiles appeared to be stable over time in the bulk soils. In contrast, contaminated rhizosphere soils revealed a clear shift of populations with removal of HMs. Rhizosphere AOB populations of the HM-contaminated soils became similar to the populations of the uncontaminated soils during phytoextraction. The effect of phytoextraction was, however, not evident in the bulk samples, which still contained large amounts of HMs. This study suggests that rhizosphere AOB populations are able to recover after the relief of HM stress by phytoextraction practices.