Phylogenetic placement in the maximum likelihood tree of the deduced formyltetrahydrofolate synthetase (FTHFS) amino acid sequences. Reference strains are given together with their accession numbers. AD anaerobic digestion, pSAOB potential syntrophic acetate-oxidising bacteria. The sulphate reducers formed a separate clade including the SAOB S. schinkii and T. phaeum as shown by Müller et al.  and were therefore excluded from the alignment. The tree was then re-build in order to reduce the size. (1) Westerholm et al. , (2) Moestedt et al. , (3) Westerholm et al. , (4) Hori et al.