Genome-Based Reclassification of Strain KIST612, Previously Classified as Eubacterium limosum, into a New Strain of Eubacterium callanderi

The strain KIST612, initially identified as E. limosum, was a suspected member of E. callanderi due to differences in phenotype, genotype, and average nucleotide identity (ANI). Here, we found that E. limosum ATCC 8486(T) and KIST612 are genetically different in their central metabolic pathways, such as that of carbon metabolism. Although 16S rDNA sequencing of KIST612 revealed high identity with E. limosum ATCC 8486(T) (99.2%) and E. callanderi DSM 3662(T) (99.8%), phylogenetic analysis of housekeeping genes and genome metrics clearly indicated that KIST612 belongs to E. callanderi. The phylogenies showed that KIST612 is closer to E. callanderi DSM 3662(T) than to E. limosum ATCC 8486(T). The ANI between KIST612 and E. callanderi DSM 3662(T) was 99.8%, which was above the species cut-off of 96%, Meanwhile, the ANI value with E. limosum ATCC 8486(T) was not significant, showing only 94.6%. The digital DNA-DNA hybridization (dDDH) results also supported the ANI values. The dDDH between KIST612 and E. callanderi DSM 3662(T) was 98.4%, whereas between KIST612 and E. limosum ATCC 8486(T), it was 57.8%, which is lower than the species cut-off of 70%. Based on these findings, we propose the reclassification of E. limosum KIST612 as E. callanderi KIST612.