Diversity of Rickettsiales in the Microbiome of the Lone Star Tick, Amblyomma americanum

Ticks are important vectors for many emerging pathogens. However, they are also infected with many symbionts and commensals, often competing for the same niches. In this paper, we characterize the microbiome ofAmblyomma americanum (Acari: Ixodidae), the lone star tick, in order to better understand the evolutionary relationships between pathogens and nonpathogens. Multitag pyrosequencing of prokaryotic 16S rRNA genes (16S rRNA) was performed on 20 lone star ticks (including males, females, and nymphs). Pyrosequencing of the rickettsialsca0 gene (also known asompA orrompA ) was performed on six ticks. Female ticks had less diverse microbiomes than males and nymphs, with greater population densities ofRickettsiales . The most common members ofRickettsiales were “Candidatus Rickettsia amblyommii” and “Candidatus Midichloria mitochondrii.” “Ca . Rickettsia amblyommii” was 2.6-fold more common in females than males, and there was no sequence diversity in thesca0 gene. These results are consistent with a predominantly vertical transmission pattern for “Ca . Rickettsia amblyommii.”