Phylogenetic tree of SRB based on dsrB amino acid sequences obtained by PCR-DGGE and in relation to cultured SRB and the closest uncultured relatives. The dsrB sequences from DNA and RNA (directly obtained from untreated fracture fluid) and substrate induced samples are represented in different colours, DNA—red, RNA—light red, CH3OH—light blue, CH3OH + SO42−—blue, CH4—light green and CH4 + SO42−—green. The band number indicates the DGGE band number in Fig. S1. Nonparametric bootstrap values are shown at nodes found in >50% of 1000 pseudoreplicates. The scale bar indicates 0.08 amino acid substitutions. The tree is rooted by Archaeglobus veneficus.