Bacterial endosymbionts from the genus Camponotus (Hymenoptera: Formicidae)

Gram-negative prokaryotic endosymbionts from follicle cells of eight species of North American Camponotus were isolated and their 16S rRNA-encoding DNA was amplified, cloned and sequenced. A BLASTn similarity search showed that the endosymbiont of Camponotus floridanus is most similar to Candidatus camponotii. Other than this ant endosymbiont, the most similar sequences were from various enterobacteria commonly found in the gut of insects and other animals. The most parsimonious phylogenetic tree generated by PAUP analysis on manually aligned sequences supports a monophyletic relationship of the ant endosymbionts when the 16S RNA sequences of two other insect-associated enterobacteria (Yersinia pestis, and Buchnera aphidicola) are included. The most parsimonious tree does not support, however, a monophyletic grouping of endosymbionts of the North American species when Old World isolates of Camponotus-associated eubacterial sequences are added to the analysis. These results suggest that the association and divergence of the endosymbiont with their ant host is ancient.