Abstract

A Gram-stain-negative, obligatory anaerobic spirochete, CHPAT, was isolated from the rectal tissue of a Holstein-Friesian cow. On the basis of 16S rRNA gene comparisons, CHPAT was most closely related to the human oral spirochete, Treponema parvum, with 88.8 sequence identity. Further characterisation on the basis of recA gene sequence analysis, cell morphology, pattern of growth and physiological profiling identified marked differences with respect to other recognised species of the genus Treponema. Microscopically, the helical cells measured approximately 1–5μm long and 0.15–0.25μm wide, with two to five irregular spirals. Transmission electron microscopy identified four periplasmic flagella in a 2 : 4 : 2 arrangement. CHPAT grew independently of serum, demonstrated no evidence of haemolytic activity and possessed an in vitro enzyme activity profile that is unique amongst validly named species of the genus Treponema, exhibiting C4 esterase, α-galactosidase and β-galactosidase activity. Taken together, these data indicate that CHPAT represents a novel species of the genus Treponema, for which the name Treponema rectale is proposed. The type strain of Treponema rectale is CHPAT (=DSM 103679T=NCTC 13848T). © 2017 IUMS.