Insights into the evolution of Cardinium: the development of a Multi Locus Sequence Typing system.

Cardinium is an intracellular reproductive manipulator in the phylum Bacteroidetes that is found in many different species of arthropods. This independently-evolved symbiont lineage exhibits three of the four reproductive phenotypes attributed to Wolbachia, including cytoplasmic incompatibility, long thought to be unique to Wolbachia-infected hosts. Genetic and phylogenetic analyses of Cardinium in comparison with Wolbachia offer an opportunity to determine functional equivalents and differences between the two lineages. Placing individual strains of Cardinium within a larger evolutionary context is currently challenging because only two genes (16S rDNA and Gyrase B) have been used to generate phylogenetic trees, and consequently, the relationship of these different strains has only been elucidated in its roughest form. The development of a Multi Locus Sequence Typing (MLST) system would provide the research community with new primers for detecting Cardinium, unambiguous methods of delineating strains, and more informative phylogenetic trees. I am in the process of designing universal Cardinium PCR primers for four different genes: Translation Elongation Factor G (EF-G), Heat Shock Protein (groEL), Iron Sulfur Cluster Assembly Protein (sufB), and Gyrase B (gyrB). These will be used to identify, describe, and place strains of Cardinium into a phylogenetic tree. Based on my preliminary tree, Cardinium appears to display more host affinity than Wolbachia. However, similar to Wolbachia, the reproductive manipulations are dispersed across the tree, and thus have likely evolved independently multiple times. To date, this is the most robust tree available for investigating Cardinium evolution.