What’s in a tortoise nose? Relationships between pathogen presence and community composition

Background/Question/Methods

Of the five Gopherus tortoise species, all but the Texas tortoise are federally listed in some capacity by the U.S. Fish and Wildlife Service. An upper respiratory tract disease (URTD) has been implicated as a cause of population declines in both the gopher tortoise (G. polyphemus) and Mojave desert tortoise (G. agassizii), and URTD has been detected in the other three Gopherus species (G. morafkai, G. berlandieri, and G. flavomarginatus). URTD is associated with mycoplasmal and Pasteurellabacteria (as well as other pathogens), and it is unknown if disease is associated with co-infections. Additionally, very little is known generally about the microbial communities present in Testudines. Here, we report on a study using 454-pyrosequencing on nasal lavage samples from each of four tortoise species in North America. The assay was conducted to quantify diversity of bacteria and presence of known disease-associated bacteria. 

Results/Conclusions

Results presented will include comparisons in upper respiratory tract microbes within and among tortoise species. Nearly 2000 OTUs were identified from 35 samples, representing 46 bacterial classes. At the bacterial genus level, principle components explain community compositions among tortoise species. With average clustering and Bray-Curtis dissimilarities, the communities found in G. agassizii and G. berlandieri are more similar within the tortoise species than those found in congeners. Presence of known pathogens will be compared to bacterial community compositions. One associated pathogen, Pasteurella testudinis, is found in all four tortoise species and in very high abundance in some samples. These results represent preliminary data on bacterial communities in tortoise nares. Future assays and analyses will be conducted to include additional sampling sites and the fifth Gopherus species, the bolson tortoise (G. flavomarginatus).