Lachnoanaerobaculum gen. nov., a new genus in the Lachnospiraceae: characterization of Lachnoanaerobaculum umeaense gen. nov., sp. nov., isolated from the human small intestine, and Lachnoanaerobaculum orale sp. nov., isolated from saliva, and reclassification of Eubacterium saburreum (Prevot 1966) Holdeman and Moore 1970 as Lachnoanaerobaculum saburreum comb. nov

Abstract

Two novel obligately anaerobic, Gram-stain-positive, saccharolytic and non-proteolytic spore-forming bacilli (strains CD3:22(T) and N1(T)) are described. Strain CD3:22(T) was isolated from a biopsy of the small intestine of a child with coeliac disease, and strain N1(T) from the saliva of a healthy young man. The cells of both strains were observed to be filamentous, approximately 5 to >20 µm long, some of them curving and with swellings. The novel organisms produced H(2)S, NH(3), butyric acid and acetic acid as major metabolic end products. Phylogenetic analyses, based on comparative 16S rRNA gene sequencing, revealed close relationships (98% sequence similarity) between the two isolates, as well as the type strain of Eubacterium saburreum and four other Lachnospiraceae bacterium-/E. saburreum-like organisms. This group of bacteria were clearly different from any of the 19 known genera in the family Lachnospiraceae. While Eubacterium species are reported to be non-spore-forming, reanalysis of E. saburreum CCUG 28089(T) confirmed that the bacterium is indeed able to form spores. Based on 16S rRNA gene sequencing, phenotypic and biochemical properties, strains CD3:22(T) and N1(T) represent novel species of a new and distinct genus, named Lachnoanaerobaculum gen. nov., in the family Lachnospiraceae [within the order Clostridiales, class Clostridia, phylum Firmicutes]. Strain CD3:22(T) (=CCUG 58757(T) =DSM 23576(T)) is the type strain of the type species, Lachnoanaerobaculum umeaense gen. nov., sp. nov., of the proposed new genus. Strain N1(T) (=CCUG 60305(T)=DSM 24553(T)) is the type strain of Lachnoanaerobaculum orale sp. nov. Moreover, Eubacterium saburreum is reclassified as Lachnoanaerobaculum saburreum comb. nov. (type strain CCUG 28089(T) =ATCC 33271(T) =CIP 105341(T) =DSM 3986(T) =JCM 11021(T) =VPI 11763(T)).

Fig. 1.

Phylogenetic tree based on 16S rRNA gene sequencing of members of Lachnoanaerobaculum gen. nov. and one species each of the other 19 recognized genera within the family Lachnospiraceae together with three remaining species of the genus Clostridium that are members of cluster XIVa. The 16S rRNA gene sequence of Clostridium butyricum VPI 3266^T served as an outgroup. Bar, 0.02 substitutions per nucleotide position.