Description of Proteiniphilum saccharofermentans sp nov., Petrimonas mucosa sp nov and Fermentimonas caenicola gen. nov., sp nov., isolated from mesophilic laboratory-scale biogas reactors, and emended description of the genus Proteiniphilum

Three novel, facultatively anaerobic bacteria of the family Porphyromonadaceae (phylum Bacteroidetes) were isolated from mesophilic laboratory-scale biogas reactors. The strains were Gram-negative rods. Optimal growth occurred between 35 and 45 degrees C and at pH 7.1-7.8. The main fermentation products were acetic and propionic acids. The predominant fatty acid in all strains was anteiso-C-15 :o, and the only respiratory quinone detected was menaquinone MK-8. 16S rRNA gene sequence comparison indicated that strains M3/6(T) and ING2-E5B(T) were most closely related to the type strain of Proteiniphilum acetatigenes, with sequence similarities of 97.3 and 94.5 %. Strain ING2-E5A(T) showed the closest affiliation to the type strain of Petrimonas sulfuriphila, with 97 % sequence identity. DNA -DNA hybridization of strain M3/6T and ING2-E5AT with the most closely related type strains showed 43.3-45.6 and 23.8-25.7 % relatedness, respectively, which supports the conclusion that both isolates represent novel species. Phylogenetic analysis and comparison of cellular fatty acid patterns indicated that strain ING2-E5BT cannot be classified as a member of any previously described genus. Therefore, because of the physiological, genotypic and chemotaxonomic differences, it is proposed to designate novel species within the genera Proteiniphilum and Petrimonas, Proteiniphilum saccharofermentans sp. nov. (type strain M3/6T=DSM 28694(T)=CECT 8610(T)=LMG 28299(T)) and Petrimonas mucosa sp. nov. (type strain ING2-E5A(T)=DSM 28695(T)=CECT 8611(T)), and a novel species of a new genus, Fermentimonas caenicola gen. nov., sp. nov. (type strain of Fermentimonas caenicola is ING2-E5B(T)=DSM 28696(T)=CECT 8609(T)=LMG 28429(T)). In addition, an emended description of the genus Proteiniphilum is provided.