Proteiniborus indolifex sp. nov., isolated from a thermophilic industrial-scale biogas plant

A novel strictly anaerobic bacterium, designated strain BA2-13 T , was isolated from a thermophilic industrial-scale biogas plant. Cells were rod-shaped and Gram-stain-positive. Growth occurred at temperatures of 25 to 50 °C and between pH 6.3 and 9.5. Strain BA2-13 T produced indole. Cell growth was stimulated by yeast extract, peptone, meat extract, a mixture of 20 amino acids, glucose, pyruvate and ribose. When grown on peptone and yeast extract, the main fermentation products were acetic acid, H 2 and CO 2 . The predominant cellular fatty acids were iso-C 15 : 0 and iso-C 14 : 0 3-OH. Major polar lipids were diphosphatidylglycerol, glycolipids, phospholipids and phosphatidylgycerol. Phylogenetic analysis based on 16S rRNA gene nucleotide sequence analysis placed strain BA2-13 T within the order Clostridiales showing closest affiliation with Proteiniborusethanoligenes with 95.9 % sequence identity. Physiological, genotypic and chemotaxonomic differences of strain BA2-13 T from P. ethanoligenes support the description of a new species within the genus Proteiniborus for which we suggest the name Proteiniborusindolifex sp. nov. (type strain BA2-13 T =DSM 103060 T =LMG 29818 T ).