Computational prediction of conserved operons and phylogenetic footprinting of transcription regulatory elements in the metal-reducing bacterial family Geobacteraceae.

Members of the family Geobacteraceae are an important group of microorganisms from the delta subdivision of Proteobacteria that couple the oxidation of organic compounds to metal reduction. In order to uncover transcription regulatory interactions in these organisms, we used computational methods to identify conserved operons and putative cis-regulatory transcription elements. We identified 26 putative operons with gene order and function conserved among two species of Geobacteraceae, Geobacter sulfurreducens and Geobacter metallireducens. Most of these operons were also conserved in Desulfovibrio vulgaris, an additional metal reducing organism from family Desulfovibrionaceae of the delta subdivision of Proteobacteria. The predicted conserved operons were investigated for the presence of transcription factor binding sites by two different methods, (i) comparison of non-coding regions in conserved operons, and (ii) neural network promoter prediction. Predicted motifs were screened to identify most likely transcription factor binding sites and ribosome-binding sites. We provide information on motifs in Geobacteraceae similar to known transcription factor binding sites in Escherichia coli, conserved motifs in other bacterial species, putative palindromic sites, and predicted ribosome-binding sites. These predictions will aid in further elucidation of regulatory networks of gene interactions in Geobacteraceae.