HIGH LEVEL ALLIANCES. “Although there are some aspects of the eukaryotic condition that have not been documented in higher-level egalitarian alliances (e.g., gene transfer between partners), even these aspects are not unique to mitochondria and plastids, as both the Paulinella and “Chlorochromatium aggregatum” cases show.”
http://www.pnas.org/content/112/33/10278.full