Development of molecular monitoring methods for the evaluation of the activity of sulfate- and metal reducing bacteria (SMRBS) as an indication of the in situ immobilisation of heavy metals and metalloids.

Sulfate- and metal reducing bacteria (SMRBs) are known for their capacity to reduce and precipitate heavy metals and metalloids (HMM) as metalsulfides (Luptáková A et al, 1998), which have the characteristic of forming stable precipitates due to their very low solubility product. Therefore, we examined the potential of using the activity of SMRBs to create a bioreactive zone or barrier for the in situ precepitation of heavy metals as a remediation strategy for heavy metal contaminated groundwater. In order to obtain insight in the ongoing biological processes for using this information to direct or optimize the in situ HMM- precipitation process, a monitoring strategy for sulfate- reduction activity of SMRBs must be designed using molecular methods. Here, we report the results of batch and column experiments which demonstrate the feasibility to stimulate the endogenous SRB- population, resulting in the in situ precipitation of HMM as sulfide complexes. Moreover, the sustainability of the in situ HMM precipitation wa s shown. For the development of molecular monitoring methods, the community structures of different bacterial consortia, obtained from bioreactors, was analysed by shotgun cloning of total community DNA followed by sequencing of the 16S rRNA- gene. The SRB- specific 16S rRNA- primerset SRB385R- 907F was used but this specificity to specifically amplify the 16S rRNA- gene of SRBs was low. Also, the dsr (dissimilatory sulfite reductase)- gene specific DSR1F- DSR4R primerset showed sometimes after amplification of the dsr- genes as part of the community structure analysis satellite bands on agarose gel. Present work is concentrating on the isolation and identification of SRB- strains in the different bacterial cultures. Shotgun cloning of the 16S rRNA- and dsr- gene of the strains and total community DNA will give the information that is necessary for the optimization of existing SRB- specific primers and design of new primers. These primers will be used for the development of monitoring techniques.