MOLECULAR CHARACTERIZATION OF A SULFATE-REDUCING CONSORTIUM WHICH MINERALIZES BENZENE

A stable and sediment-free, benzene mineralizing, sulfate-reducing cul ture that resisted repeated attempts at isolation was examined using m olecular approaches such as traditional cloning and sequencing and a d irect PCR fingerprinting method for 16S rRNA genes. Despite the cultur e's long exposure to benzene as the only carbon and energy source (ove r 3 years) and repeated dilutions of the original enrichment, this con sortium has remained relatively complex. Cloning and sequence analysis identified 12 unique small subunit rRNA genes. The 16S rRNA genes bel ong to different eubacterial phyla, including Proteobacteria, Cytophag ales and Gram-positives. There is one deeply branching clone which is not closely related to any known, sequenced, bacterium. A different cl one, however, is closely related to a known sulfidogenic, aromatic hyd rocarbon degrader. To assess 16S rRNA gene cloning efficiency, a finge rprinting method based on fluorescent, end-labeling of PCR product (16 S rRNA genes) and screening by restriction length polymorphism analysi s (PFLP) was employed. The data obtained indicated that we had cloned and characterized nearly all of the eubacterial 16S rRNA genes amplifi ed from the consortia. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.