Abstract
Seventeen anaerobic, Gram-negative, tiny coccobacilli were collected in France from various human clinical samples. Biochemical analyses as well as molecular studies, including 16S rRNA and dnaK gene sequencing, affiliated all the isolates to the genus Dialister . However, 16S rRNA and dnaK gene sequence similarities were below 95·2 and 79·7 %, respectively, when comparisons were performed with the currently described species Dialister pneumosintes and Dialister invisus . Two clusters consisting of 13 and four isolates could be differentiated. 16S rRNA- and dnaK -based phylogeny confirmed that these two clusters represent two novel and distinct lineages within the genus Dialister . Finally, phenotypic, genotypic and phylogenetic data supported the proposal of the two novel species Dialister micraerophilus sp. nov. (type strain ADV 04.01 T =AIP 25.04 T =CIP 108278 T =CCUG 48837 T ) and Dialister propionicifaciens sp. nov. (type strain ADV 1053.03 T =AIP 26.04 T =CIP 108336 T =CCUG 49291 T ). The G+C content of the DNA of the D. micraerophilus type strain is 36·3 mol%. On the basis of 16S rRNA gene sequence analysis, 11 isolates originating from Canada could also be affiliated to D. micraerophilus sp. nov., and were included in the species description.