Fig. 1

Dynamics of the acetogenic community in SAO1 (low-ammonia control digester) and SAO3 (high-ammonia experimental digester) traced by formyltetrahydrofolate synthetase (fhs) gene profiling using terminal restriction fragment length polymorphism (T-RFLP). Terminal restriction fragments (T-RFs) that could be affiliated to fhs genotypes are labelled by fragment size (bp) and operational taxonomic unit (OTU) affiliation or accession number. T-RFs were grouped into equally behaving fragments: Not establishing under either condition (blue 50, 159 bp), stable fragments in the control but fading in the experimental digester (green 86, 253, 238, 309, 477, 593 bp), establishing fragments up to 0.62 g NH₃/L in the experimental digester, not detected in the control (orange 76, 220, 236/7, 240, 339, 442, 553, 590 bp), establishing fragments up to 0.96 g NH₃/L in the experimental digester, not detected in the control (red 283, 379, 446, 471, 591 bp), exclusively detected at sample point day 442 in experimental digester (pink 60, 296, 463, 495/6, 520 bp). Fragments marked in black remained uncut. Peaks that emerged non-chronologically on one or two occasions are marked in grey. Days of operation are plotted on the x-axis, relative peak abundance on the y-axis