Molecular diversity and distribution of aromatic hydrocarbon-degrading anaerobes across a landfill leachate plume.

Natural attenuation of the mono-aromates benzene, toluene, ethylbenzene and xylene occurs under iron-reducing conditions in a leachate-contaminated aquifer near the Banisveld landfill, the Netherlands. The diversity of mono-aromate-degrading microorganisms was studied by targeting functional genes encoding benzylsuccinate synthase α-subunit (bssA) and 6-oxocyclohex-1-ene-1-carbonyl-CoA hydrolase (bamA). Sixty-four bssA and 188 bamA variants were sequenced from groundwater sampled along the pollution plume in 1999 and 2004. Species containing bssA sequences closest affiliated (>91%) with the betaprotebacterium Georgfuchsia toluolica were the dominant alkylbenzene degraders (89% of bssA sequences). bssA genes were found at more than 10-fold lower copy numbers than bamA genes, of which only a small fraction (