Campylobacter geochelonis sp nov isolated from the western Hermann's tortoise (Testudo hermanni hermanni)

During a screening study to determine the presence of species of the genus Campylobacter in reptiles, three putative strains (RC7, RC11 and RC20(T)) were isolated from different individuals of the western Hermann's tortoise (Testudo hermanni hermanni). Initially, these isolates were characterized as representing Campylobacter fetus subsp. fetus by multiplex PCR and partial 16S rRNA gene sequence analysis. Further whole- genome characterization revealed considerable differences compared to other Campylobacter species. A polyphasic study was then undertaken to determine the exact taxonomic position of the isolates. The three strains were characterized by conventional phenotypic tests and whole genome sequencing. We generated robust phylogenies that showed a distinct clade containing only these strains using the 16S rRNA and atpA genes and a set of 40 universal proteins. Our phylogenetic analysis demonstrates their designation as representing a novel species and this was further confirmed using whole- genome average nucleotide identity within the genus Campylobacter (similar to 80 %). Compared to most Campylobacter species, these strains hydrolysed hippurate, and grew well at 25 degrees C but not at 42 degrees C. Phenotypic and genetic analyses demonstrate that the three Campylobacter strains isolated from the western Hermann's tortoise represent a novel species within the genus Campylobacter, for which the name Campylobacter geochelonis sp. nov. is proposed, with RC20(T) (=DSM 102159(T) =LMG 29375(T)) as the type strain.