Schaedlerella arabinosiphila gen. nov., sp. nov., a D-arabinose-utilizing bacterium isolated from faeces of C57BL/6J mice that is a close relative of Clostridium species ASF 502

The use of gnotobiotics has attracted wide interest in recent years due to technological advances that have revealed the importance of host-associated microbiomes for host physiology and health. One of the oldest and most important gnotobiotic mouse model, the altered Schaedler flora (ASF) has been used for several decades. ASF comprises eight different bacterial strains, which have been characterized to different extent, but only a few are available through public strain collections. Here, the isolation of a close relative of one of the less-studied ASF strains, Clostridium species ASF 502, from faeces of C57BL/6J mice is reported. Isolate TLL-A1T shares 99.5 % 16S rRNA gene sequence identity with Clostridium species ASF 502 and phylogenetic analyses indicate that both strains belong to the uncultured so-called ‘Lachnospiraceae UCG 006’ clade. The rare sugar d-arabinose was used as a sole carbon source in the anaerobic isolation medium. Results of growth experiments with TLL-A1T on different carbon sources and analysis of its ~6.5 Gb indicate that TLL-A1T harbours a large gene repertoire that enables it to utilize a variety of carbohydrates for growth. Comparative genome analyses of TLL-A1T and Clostridium species ASF 502 reveal differences in genome content between the two strains, in particular with regards to carbohydrate-activating enzymes. Based on genomic, molecular and phenotypic differences, we propose to classify strain TLL-A1T (DSM 106076T=KCTC 15657T) as a representative of a new genus and a new species, for which we propose the name Schaedlerella arabinosiphila gen. nov., sp. nov.