ABSTRACT
Five strains of butyrate-producing, anaerobic, gram-positive bacteria were isolated from human faecal material. These strains were slightly curved rods that showed motility by means of multiple subterminal flagella. The DNA G + C content of the strains was 29-31 mol%. A detailed investigation of the phenotypic and phylogenetic characteristics of the strains revealed that they represent a novel species of anaerobic, low-G+C-content, butyrate-producing bacterium that shows net acetate utilization during growth on media containing carbohydrates and short-chain fatty acids. The 16S rRNA gene sequences of the five isolates were determined and they confirmed that these strains were closely related to each other. Phylogenetic analysis indicated that the most closely related species are Eubacterium rectale, Eubacterium oxidoreducens and Roseburia cecicola, members of cluster XIVa of the Clostridium subphylum of gram-positive bacteria, although they share less than 95% sequence identity with the novel strains. It is proposed that a novel species, Roseburia intestinalis sp. nov., be created, with strain L1-82T (= DSM 14610T = NCIMB 13810T) as the type strain.
Subject(s)
Gram-Positive Rods/classification , Gram-Positive Rods/isolation & purification , Base Composition , Butyrates/metabolism , Clostridium/classification , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , DNA, Ribosomal/genetics , Eubacterium/classification , Feces/microbiology , Fermentation , Gram-Positive Rods/metabolism , Gram-Positive Rods/ultrastructure , Humans , Microscopy, Electron, Scanning , Molecular Sequence Data , Phylogeny , RNA, Bacterial/genetics , RNA, Ribosomal, 16S/genetics , Terminology as TopicABSTRACT
Seven strains of Roseburia sp., Faecalibacterium prausnitzii, and Coprococcus sp. from the human gut that produce high levels of butyric acid in vitro were studied with respect to key butyrate pathway enzymes and fermentation patterns. Strains of Roseburia sp. and F. prausnitzii possessed butyryl coenzyme A (CoA):acetate-CoA transferase and acetate kinase activities, but butyrate kinase activity was not detectable either in growing or in stationary-phase cultures. Although unable to use acetate as a sole source of energy, these strains showed net utilization of acetate during growth on glucose. In contrast, Coprococcus sp. strain L2-50 is a net producer of acetate and possessed detectable butyrate kinase, acetate kinase, and butyryl-CoA:acetate-CoA transferase activities. These results demonstrate that different functionally distinct groups of butyrate-producing bacteria are present in the human large intestine.
