Ureaplasma rhincodontis sp. nov. isolated from the faeces of whale shark (Rhincodon typus).

A novel strain of the genus Ureaplasma, designated TOSA-KAIYUT, was isolated from the faeces of a whale shark (Rhincodon typus). This study reports the first isolation of a member of the genus Ureaplasma from a poikilothermic vertebrate. TOSA-KAIYUT was characterized phenotypically and genotypically and compared with known species of the genus Ureaplasma. TOSA-KAIYUT hydrolysed urea, but arginine catabolism and acid production from glucose were not detected under the aerobic conditions tested. TOSA-KAIYUT grew in serum- and urea-supplemented pleuropneumonia-like organism (PPLO) broth under both aerobic and anaerobic conditions at 25 °C; however, colour-changing unit titres were 10-100-fold higher under anaerobic conditions and colony formation on PPLO agar occurred only under anaerobic conditions. Transmission electron microscopy revealed a typical mollicute cellular morphology. 16S rRNA gene sequence analysis indicated that the most closely related type strain of a species with a validly published name was Ureaplasma ceti JCM 39153T (92.8% similarity). The average nt identity and digital DNA-DNA hybridization values between TOSA-KAIYUT and closely related species were below the accepted thresholds for species delineation. Phylogenetic analysis further showed that TOSA-KAIYUT belongs to an uncultured-dominated clade of the genus Ureaplasma, together with U. ceti, which has previously been the only cultured representative of this lineage. Based on the genomic, phenotypic and phylogenetic properties, TOSA-KAIYUT represents a novel species of the genus Ureaplasma, for which the name Ureaplasma rhincodontis sp. nov. with type strain TOSA-KAIYUT (=JCM 39612T =KCTC 25996T) is proposed. The genomic G+C content and draft genome size of the type strain were 26.0 mol% and 625,683 bp, respectively.