Catabolic Gene Probe Analysis of an Aquifer Microbial Community Degrading Creosote-Related Polycyclic Aromatic and Heterocyclic Compounds S.G. Hosein, 1 D. Millette, 1 * B.J. Butler, 2 C.W. Greer 1 1 Biotechnology Research Institute, National Research Council Canada, 6100 Royalmount Ave., Montreal, Quebec, Canada, H4P 2R2 2 Waterloo Centre for Groundwater Research, University of Waterloo, Waterloo, Ontario, Canada Received: 26 January 1996; Accepted: 20 June 1996 A B S T R A C T The biodegradation of a mixture of several creosote-related compounds, p-cresol, phenanthrene, fluorene, and carbazole was examined in columns containing aquifer sands. The aquifer material, itself, had an effect on the migration of the test compounds, with p-cresol being retarded the least, followed by carbazole, then fluorene, and finally phenanthrene. The biodegradation of all the compounds was greatly enhanced by the inclusion of p-cresol (10 ppm) in the substrate mixture. Associated with this enhanced degradation was a 100-fold increase in the total culturable bacterial population, and increases in the xylE- and ndoB-positive bacterial populations of more than three orders of magnitude. The products of these two genes are involved in the degradation of monocyclic and polycyclic aromatic compounds, respectively. In columns that did not receive p-cresol, there was no significant change in either the total culturable bacterial population density or the xylE- positive bacterial population, but there were significant increases of one to two orders of magnitude in the ndoB-positive bacterial populations. The results suggest that the ndoB gene probe can detect bacteria capable of utilizing phenanthrene, carbazole, and possibly fluorene. Introduction Creosote, a widely used wood preserving agent, is a mixture of approximately 200 compounds, of which 85% are poly- cyclic aromatic hydrocarbons (PAHs), 10% are phenolics, and 5% are N-S-O heterocycles [23]. When present in groundwater, creosote compounds pose a threat to public health because many are highly toxic and/or carcinogenic [20]. Leachates from creosote-contaminated sites have been reported to have concentrations of phenols from 10 to 800 mg/l, N-S-O compounds from 1 to 25 mg/l, and PAHs from 1 to 25 mg/l [4]. The biodegradation of PAHs has been reported to be catalyzed by a wide variety of bacteria, fungi, and algae [7]. The white-rot fungus Phanerochaete chrysosporium has been shown to biodegrade mixtures of some of the major com- * Present address: SNC-LAVALIN Environment Inc., Place Felix Martin, 455 Rene Levesque Blvd. West, Montreal, Que., Canada, H2Z 1Z3. Correspondence to: Charles W. Greer. MICROBIAL ECOLOGY Microb Ecol (1997) 34:81–89 © 1997 Springer-Verlag New York Inc.