Two related anaerobic strains, designated as SWB101512T and SWB19611, were isolated from the bronchoalveolar lavage fluid of two lung cancer patients. Cells were Gram-stain-positive, non-motile and non-spore-forming. Growth could be observed at 26–45 °C (optimum, 37 °C), pH 5.0–8.5 (optimum, pH 7.0) and with 0.5–2.0 % (v/w) NaCl (optimum, 1.0%). The 16S rRNA gene sequences of SWB101512T and SWB19611 showed the highest similarities to
Denitrobacterium detoxificans
DSM 21843T (91.1 and 91.3 %, respectively). The phylogenetic tree based on the 16S rRNA gene sequences and the core genome sequences demonstrated that the two strains clustered together and formed a distinct lineage within the family
Eggerthellaceae
. The DNA G+C contents of strains SWB101512T and SWB19611 were 62.0 and 61.9 mol%, respectively. The predominant cellular fatty acids of strains SWB101512T and SWB19611 were C16 : 0 DMA (27.8 and 28.8 %, respectively). The respiratory menaquinone in both strains was menaquinone 6 and the polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, two phospholipids, three glycolipids and three unidentified lipids. Based on evidence from phenotypic, chemotaxonomic and genomic analyses, a new genus and species belonging to the family
Eggerthellaceae
, named Curtanaerobium respiraculi gen. nov., sp. nov. is proposed. The type strain is SWB101512T (=GDMCC 1.2991T=JCM 35330T).