Fig. 2

a Cluster analysis of DGGE fingerprints based on the PCR of archaeal 16S rRNA genes extracted from undigested cattle slurry (CS) and sludges after anaerobic digestion at 37 °C. WR Wood residues, PR Pulp residues, 37 Anaerobic digestion at 37 °C, au autoclave pretreatment, us ultrasound pretreatment, al alkaline pretreatment, mo commercial microorganism mixture addition, en enzyme pretreatment. b Cluster analysis of DGGE fingerprints based on the PCR of archaeal 16S rRNA genes extracted from cattle slurry and sludges after anaerobic digestion at 37 and 55 °C. CS cattle slurry, WR wood residues, PR pulp residues, 37 anaerobic digestion at 37 °C, 55 anaerobic digestion at 55 °C