An ancient endosymbiosis of an α-proteobacterium produced a diverse range of organelles including mitochondria. Reconstruction of the Pygsuia biforma proteome adds to the mosaic of functional systems present in mitochondrial-related organelles and demonstrates the role of horizontal gene transfer.

Phylogenetic analyses show the single origin of a plastid metabolite translocator family in the Plantae from a gene encoding an existing endomembrane-derived protein. Red algal secondary endosymbiosis has spread a translocator gene into the ancestor of the "chromalveolate" protists, where it has diversified into a novel clade of proteins.

Wolbachia, a maternally transmitted bacterium globally present in arthropods, favors its own transmission by producing dramatic changes in host reproduction. Insight into the underlying molecular and cellular mechanisms comes from the identification of the Wolbachia effector protein TomO, which maintains host germline stem cells in an undifferentiated state.

Many eukaryotic organisms have symbiotic associations with obligate intracellular bacteria. The clonal transmission of endosymbionts between host generations should lead to the irreversible fixation of slightly deleterious mutations in their non-recombinant genome by genetic drift. However, the stability of endosymbiosis indicates that some mechanism is involved in the amelioration of the effec...