Eubacterium album sp. nov., a butyrate-producing bacterium isolated from faeces of a healthy human

Abstract

An oval to rod-shaped, Gram-stain-positive, strictly anaerobic bacterium, designated LFL-14T, was isolated from the faeces of a healthy Chinese woman. Cells of the strain were non-spore-forming, grew optimally at 37 °C (growth range 30–45 °C) and pH 7.0 (growth range 6.0–9.0) under anaerobic conditions in the liquid modified Gifu anaerobic medium (mGAM). The result of 16S rRNA gene-based analysis indicated that LFL-14T shared an identity of 94.7 0% with Eubacterium ventriosum ATCC 27560T, indicating LFL-14T represented a novel taxon. The results of genome-based analysis revealed that the average nucleotide identity (ANI), the digital DNA–DNA hybridisation (dDDH) and average amino acid identity (AAI) between LFL-14T and its phylogenetically closest neighbour, Eubacterium ventriosum ATCC 27560T, were 77.0 %, 24.6 and 70.9 %, respectively, indicating that LFL-14T represents a novel species of the genus Eubacterium. The genome size of LFL-14T was 2.92 Mbp and the DNA G+C content was 33.14 mol%. We analysed the distribution of the genome of LFL-14T in cohorts of healthy individuals, type 2 diabetes patients (T2D) and patients with non-alcoholic fatty liver disease (NAFLD). We found that its abundance was higher in the T2D cohort, but it had a low average abundance of less than 0.2 % in all three cohorts. The percentages of frequency of occurrence in the T2D, healthy and NAFLD cohorts were 48.87 %, 16.72 % and 13.10 % respectively. The major cellular fatty acids of LFL-14T were C16 : 0 (34.4 %), C17 : 0 2-OH (21.4 %) and C14 : 0 (11.7 %). Additionally, the strain contained diphosphatidylglycerol (DPG) and phosphatidylethanolamine (PE), as well as unidentified phospholipids and unidentified glycolipids. The glucose fermentation products of LFL-14T were acetate and butyrate. In summary, On the basis of its chemotaxonomic, phenotypic, phylogenetic and phylogenomic properties, strain LFL-14T (= CGMCC 1.18005T = KCTC 25580T) is identified as representing a novel species of the genus Eubacterium, for which the name Eubacterium album sp. nov. is proposed.