Cardinium

"Candidatus Cardinium" is a genus of Gram-negative parasitic bacteria that reside within cells of some arthropods and nematodes.

[1][2] Although they have not yet been isolated in pure culture (hence the designation Candidatus), they are known to negatively influence reproduction in their hosts in order to further their own proliferation.

One of the only other examples of this type of parasitism is the genus Wolbachia, which also infects arthropods.

[4] "Candidatus Cardinium" bacteria use many of the same methods to interfere with host reproduction as Wolbachia, including inducing cytoplasmic incompatibility and distorting the sex ratio in the host population to favor females.

[5] "Candidatus Cardinium" bacteria are maternally inherited; infections are maintained through generations through the egg cells (termed vertical transmission).

This image is a set of phylogenetic trees based on various sequencing data. It includes two Wolbachia genes and Cardinium 16S rRNA sequence data, along with a reference P-endosymbiont and Arsenophonus .