Unveiling hidden diversity within Arcobacter cryaerophilus: a description of Arcobacter crypticus sp. nov., Arcobacter occultus sp. nov. and Arcobacter thermotolerans sp. nov., and an emended description of Arcobacter cryaerophilus.

Arcobacter cryaerophilus is genomically heterogeneous with a type strain that is aberrant from most other strains in this species. Consequently, several infraspecific subdivisions have been introduced, including DNA-DNA hybridization groups, subgroups and genomovars. Recent comparative whole-genome sequence studies have corroborated and extended this heterogeneity and revealed the presence of four species among historical strains and new isolates which are now classified as A. cryaerophilus. The present study aimed to establish a simple formal classification of A. cryaerophilus-like bacteria that facilitate transparent communication by integrating genome sequence data of taxonomically well-characterized strains with biochemical characteristics. To this end, we propose three novel species: Arcobacter crypticus sp. nov. [with strain LMG 9065T (=CCUG 12019T) as the type strain], Arcobacter occultus sp. nov. [with strain LMG 29976T (=CCUG 17808T) as the type strain] and Arcobacter thermotolerans sp. nov. [with LMG 10829T (=ATCC 49615T) as the type strain]. This revised classification provides a robust basis for future investigations into the ecological roles and pathogenic potential of these taxa.