The survival of the pentachlorophenol-degrading Rhodococcus chlorophenolicus PCP-1 and Flavobacterium sp. in natural soil

The survival of two different pentachlorophenol (PCP)-degrading bacteria were studied in natural soil. The PCP-degraders Rhodococcus chlorophenolicus and Flavobacterium sp., both able to mineralize PCP into CO₂ and chloride in axenic culture, were tested for the capacity to survive and degrade PCP in natural soil. These bacteria were immobilized on polyurethane (PUR) foam and introduced into natural peaty soil to give about 10⁹ cells g^-1 of soil (dry weight). R. chlorophenolicus induced PCP-degrading activity in soil remained detectable for 200 days whether or not a carbon source was added (distillery waste or wood chips). Electron microscopic investigation performed almost a year after inoculation, revealed the presence of R. chlorophenolicus-like cells in the PUR foam particles. PCP-degrading activity of Flavobacterium sp. declined within 60 days of burial in the soil without enhancing the PCP removal. R. chlorophenolicus degraded PCP in soil at a mean rate of 3.7 mg of PCP day^-1 kg^-1 of soil, which corresponds to ca. 5×10^-3 pg of PCP degraded per inoculated R. chlorophenolicus cell day^-1. The solvent extractable organic chlorine contents of the soil decreased stoichiometrically (>95%) with that of PCP indicating that PCP was essentially mineralized.Abbreviations ATCC American type culture collection - DSM Deutsche Sammlung für Mikroorganismen - DW distillery waste - EM electron microscopy - EOX extractable organic halogen - GC/ECD gas chromatograph/electron capture detector - GC/MS gas chromatograph/mass spectrometer - PCP pentachlorophenol - WC wood chips - d.wt. dry weight - w.wt. wet weight - d.s. dry soil - d.H₂O distilled water - PCA polychlorinated aromatics