Bacterial community shifts in a peat-forest soil spiked with 3-chlorobenzoate (3CBA) or 2,5-dichlorobenzoate (2,5DCB) were monitored by PCR-amplification of the V6 to V8 regions of the 16S rRNA and rDNA, followed by separation of the amplicons by temperature gradient gel electrophoresis. 3CBA disappeared to non-detectable levels after 15 days by a biologically mediated process, while 2,5DCB remained at the initial concentration values. The experiments were conducted under microcosms systems. Addition of the chlorinated benzoates to the soil resulted in a rapid decrease of the microbial diversity, as judged by a time-dependent reduction in the number of amplicons detected by temperature gradient gel electrophoresis. Few amplicons specifically enriched in the spiked soils were cloned and characterised by sequence analysis. The identity of the cloned DNA and the corresponding soil amplicons was confirmed by hybridisation with a radioactively labelled V6-probe. Analysis of the 16S rDNA sequences indicated that Burkholderia-related bacteria dominated the enriched soil populations under 3CBA stress. In addition, enrichment cultures growing on 3CBA as sole C-source were obtained from the respective spiked soil, which were found to contain bacteria with identical 16S rDNA sequences as those induced by 3CBA stress in soil.