In situ polychlorophenol bioremediation potential of the indigenous bacterial community of boreal groundwater

The composition and chlorophenol-degrading potential of groundwater bacteri al community in a permanently cold, oxygen-deficient chlorophenol contamina ted aquifer at Karkola Finland was studied with the aim of evaluating bl si tu bioremediation potential. The groundwater contained from 10(4) to 10(7) microscopically counted cells/ml and up to 10(5) CFU/ml heterotrophic bacte ria cultivable at 8 and 20 degreesC. Of the 102 pure cultures, of which 86% Gram-negative, from the plume area (10,000 mug of chlorophenols/l), 57% de graded 2, 3, 4, 6-tetrachlorophenol (TeCP), the main component of the wood preservative which was the source of contamination; 17% also degraded penta chlorophenol (PCP). The degraders were scattered among 16 different cluster s of Gram-negatives mainly proteobacteria and members of Cytophaga/Flexibac tel/Bacteroides phylum judged by the composition of whole-cell fatty acids. Only one Gram-positive degrading cluster was found containing seven actino bacteria closest to Nocardioides. Of the 88 pure cultures isolated from out side the plume (< 10 mug of chlorophenols/l) 67% were Gramnegative. Seven p ercent of the isolates degraded 2, 3, 4, 6-TeCP and/or PCP. Five of the Gra m-positive isolates from outside the plume were Mycobacterium/Rhodococcus-r elated actinobacteria and O-methylated 2, 3, 4, 6-TeCP and PCP. The results show that chlorophenol degrading bacterial flora had been enriched as a re sult of contamination of the aquifer. This suggests significant in situ bio remediation potential of the site. (C) 2001 Elsevier Science Ltd. All right s reserved.