Heavy metals are a significant source of pollution in soils that have been demonstrated to exert significant toxic effects on soil microbial communities. Here, we investigate the impact of the heavy metals lead and zinc on the bacterial community of an upland metallophytic grassland the UK, contaminated by historical lead mining activity. We focus on the total microbial diversity and that of the Actinobacteria, a significant component of the aerobic soil community that demonstrate a broad metabolic activity and represent useful indicators of soil health. Two experimental approaches were adopted, the first employed microcosms containing soil from the site of an abandoned lead mine spoil heap, bacterial diversity was investigated using denaturing gradient gel electrophoresis (DGGE) of PCR amplified 16S rRNA DNA with universal primers to amplify the total community and more specific Actinobacteria primers. The Actinobacteria specific PCR primers showed that this taxon represented a diverse and metabolically active element of the microbial community of lead contaminated upland soil. Subsequently, we investigated how the stability of the bacterial communities responded to an increase in stress by adding additional Pb and Zn to the soil. There is significant interest in determining whether communities under stress are more or less robust in the face of additional environmental stress. Our data was equivocal, the total community diversity responded negatively to additional heavy metal input into the soil, whereas, the Actinobacteria community did not show any substantial change in its diversity. A second experiment characterised the bacterial soil community along a transect of a metallophytic grassland site that had significant differences in the Pb, Zn, organic C and N content across it. In this study the metabolically active bacterial population was studied using reverse transcription of mRNA from16S rRNA gene. Universal primers showed a low diversity of metabolically active bacteria, and both organic C and heavy metal concentrations in the soil seemed to impact on the community diversity. In contrast Actinobacteria showed higher diversities and seemed to be able to maintain this diversity even in soils with low organic C and high heavy metal concentrations suggesting that they are competitive in this stressed environment with other soil flora. The data presented here may prove useful in determining the effect of heavy metal concentrations on soil microbial diversity and community stability, particularly in managing rare metallophytic grassland sites and more widely in remediating contaminated soils.
|Title of host publication||Microbial Ecology Research Trends|
|Publisher||Nova Science Publishers, Inc.|
|Number of pages||37|
|Publication status||Published - 1 Jan 2008|