Diversity of chlorophenol-degrading bacteria isolated from contaminated boreal groundwater

Chlorophenol-degrading bacteria from a long-term polluted groundwater aquifer were characterized. All isolates degraded 2,4,6-trichlorophenol and 2,3,4,6-tetrachlorophenol at concentrations detected in the contaminated groundwater (< 10 mg 1(-1)). Pentachlorophenol was degraded by three isolates when present alone. In two gram-positive isolates, 2,3,4,6-tetrachlorophenol was required as an inducer for the degradation of pentachlorophenol. The gram-positive isolates were sensitive to pentachlorophenol, with an IC50 value of 5 mg/l. Isolates belonging to the Cytophaga/Flexibacter/Bacteroides phylum had IC50 values of 25 and 63 mg/l. Isolates belonging to alpha-, beta- and gamma-Proteobacteria generally tolerated the highest pentachlorophenol concentrations (> 100 mg/l). Polychlorophenol-degrading capacity was found in strains of Nocardioides, Pseudomonas, Ralstonia, Flavobacterium, and Caulobacter previously not known to degrade polychlorophenols. In addition, six polychlorophenol-degrading sphingomonads were found.