Plasmid Transfer and Catabolic Gene Distribution in the Area of a Groundwater Bioremediation System

Abstract

Landfill leachate from the Hyde Park chemical landfill site within the Niagara River watershed has provided a unique opportunity to characterize the evolution of microbial populations able to degrade chlorinated organic compounds. The landfill has been in operation since the early 1970s and has recently undergone bioremediation using trenching, groundwater collection and sequencing batch reactor technologies. The structure and distribution of IncPβ plasmid and chromosomal determinants encoding the degradation of chlorobenzoates (cbaABC, clcABD and dehalogenase genes) have been studied. Enrichments from groundwater wells, the bioremediation facility, and surface water/leachate runoff in the vicinity of Hyde Park have indicated the geographical distribution of these genetic elements. A decline in genotype frequencies is observed at sites further from the landfill. The known genotypes account for less than 10% of the degradative phenotypes isolated from these samples. There is some variation in the genetic structure of the known genotypes, as determined by plasmid analysis and restriction digestion patterns. The distribution of cbaABC and clcABD genotypes within different host species is a function of the phylogenetic position of the host bacterium and of the biochemistry of aromatic compound degradation in these different hosts.