Community analyses of sulfidogenic 2-bromophenol-dehalogenating and phenol-degrading microbial consortia

Microbial consortia were enriched under sulfidogenic conditions using a com mon estuarine sediment inoculum with 2-bromophenol or phenol as the sole th e carbon source. Stable consortia were maintained over a 3-year period with repeated feeding and serial dilution into fresh medium. 2-Bromophenol was initially dehalogenated to phenol. Degradation of phenol was dependent on s ulfate reduction and inhibited by molybdate, a specific inhibitor of sulfat e reduction. Reductive dehalogenation of 2-bromophenol, however, was not de pendent on, or inhibited by sulfate. The 2-bromophenol- and phenol-degradin g sulfidogenic consortia were characterized using 16S rRNA restriction frag ment length polymorphism analysis and unique clones were sequenced. Termina l restriction fragment length polymorphism of all individual clones and bot h microbial consortia indicated that all 16S rRNA types present in the cons ortia were cloned and characterized. Four phylotypes were identified from t he 2-bromophenol-utilizing consortium which based upon their 16S rRNA seque nces clustered into three major groups: one sequence was related to the eps ilon-subgroup of the Proteobacteria, two clones clustered within the sulfat e-reducers (delta-subgroup of Proteobacteria), the fourth phylotype was div ergent from previously described bacteria and was most closely related to t he genus Planctomycetes. None of the clones from the 2-bromophenol-degradin g consortium are close to previously described aryl-dehalogenating bacteria which predominantly comprise the genera Desulfitobacterium and Desulfomoni le. In contrast, the phenol-degrading consortium yielded only two clonal ty pes. One was placed within the epsilon-sub-division of the Proteobacteria w ith Thiomicrospira denitrificans as its closest neighbor. The other clone w as closest to the genus Cytophaga with Anaeroflexus maritimus as its closes t neighbor. (C) 1999 Federation of European Microbiological Societies. Publ ished by Elsevier Science B.V. All rights reserved.