Torix Rickettsia are widespread in arthropods

Rickettsia are intracellular bacteria best known as the causative agents of several human and animal diseases. Although these medically important Rickettsia are often transmitted via haematophagous arthropods, other Rickettsia, such as those in the Torix group, are found to reside exclusively in arthropods and protists with no secondary vertebrate host. Importantly, little is known about the biology of Torix group Rickettsia. This study describes the serendipitous discovery of Rickettsia amplicons in the Barcode of Life Data System (BOLD), a sequence database specifically designed for the curation of DNA barcodes (a widely used tool for species identification). Out of >185,000 barcode sequences analysed, Rickettsia is observed in approximately 0.42% of barcode submissions and is more likely to be found compared to Wolbachia (0.26%). Through phylogenetic analysis of these non-target bacterial amplicons, the Torix group of Rickettsia are shown to account for 95% of all unintended amplifications from the genus. Furthermore, via re-barcoding of BOLD DNA templates, alongside a targeted Rickettsia screen using PCR assay and a bioinformatic screen of the Sequence Read Archive (SRA), we show Torix Rickettsia are more widespread in arthropods than previously thought. A broad range of host diversity associated with Torix Rickettsia is uncovered, including phloem-feeding bugs, parasitoid wasps, forest detritivores and vectors of disease. The unknown host effects and transmission strategies of these endosymbionts makes these newly discovered associations important to inform future directions of investigation involving the understudied Torix Rickettsia.