Acholeplasma testudinis sp. nov., Isolated from the Nares of the Florida Gopher Tortoise (Gopherus polyphemus)

Gopher tortoises (Gopherus polyphemus) are an environmentally threatened keystone species, whose burrows provide food and shelter for over 300 animal species. As part of an intensive field study of 11 wild gopher tortoise populations in Florida, we obtained clinical isolates (N=12) from the nares of tortoises. Based on 16S rRNA sequencing, one isolate was identified as Acholeplasma hippikon but the other 11 isolates grouped together and were distinct from other known Acholeplasma spp. The clinical isolates (N=11) from tortoises from 7 different geographical sites in north central Florida were characterized phenotypically and by 16S rRNA, whole genome sequence, and proteome phylogenies as a new species. Based on the isolation source history, phenotypic, and phylogenetic characteristics, we propose the name Acholeplasma testudinis sp. nov.; strain ORD1043 was chosen as the Type strain. To determine potential pathogenicity, tortoises were inoculated intranasally with either 108 CFU of A. testudinis ORD1043Ts (N=9, Infected) or sterile SP4 broth (N=7, Control). Tortoises were followed throughout the study for occurrence of clinical signs, necropsied at 91 days post infection, and histological lesions in the upper respiratory tract determined. Despite the high infectious dose used, mean clinical sign scores were very low and mild overall, and histopathological lesions were not consistently observed in the infected group. We therefore concluded that A. testudinis is not a significant pathogen but is a likely commensal that can colonize the tortoise but does not cause significant disease or tissue damage to the host.