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

Microbial consortia were enriched under sulfidogenic conditions using a common estuarine sediment inoculum with 2‐bromophenol or phenol as the sole the 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 sulfate reduction and inhibited by molybdate, a specific inhibitor of sulfate reduction. Reductive dehalogenation of 2‐bromophenol, however, was not dependent on, or inhibited by sulfate. The 2‐bromophenol‐ and phenol‐degrading sulfidogenic consortia were characterized using 16S rRNA restriction fragment length polymorphism analysis and unique clones were sequenced. Terminal restriction fragment length polymorphism of all individual clones and both microbial consortia indicated that all 16S rRNA types present in the consortia were cloned and characterized. Four phylotypes were identified from the 2‐bromophenol‐utilizing consortium which based upon their 16S rRNA sequences clustered into three major groups: one sequence was related to the ϵ‐subgroup of the Proteobacteria, two clones clustered within the sulfate‐reducers (δ‐subgroup of Proteobacteria), the fourth phylotype was divergent from previously described bacteria and was most closely related to the genus Planctomycetes . None of the clones from the 2‐bromophenol‐degrading consortium are close to previously described aryl‐dehalogenating bacteria which predominantly comprise the genera Desulfitobacterium and Desulfomonile . In contrast, the phenol‐degrading consortium yielded only two clonal types. One was placed within the ϵ‐sub‐division of the Proteobacteria with Thiomicrospira denitrificans as its closest neighbor. The other clone was closest to the genus Cytophaga with Anaeroflexus maritimus as its closest neighbor.