Pathogen to powerhouse: How did the precursors to the mitochondrion and the plastid evade host defense?

read in Science  12 Feb 2016 by S. Ball, D. Bhattacharya, and A. Weber:
Mitochondria and plastids are essential for harnessing energy in eukaryotic cells. They are believed to have formed through primary endosymbioses, in which bacterial symbionts were converted into energy-producing organelles. The first challenges for an endosymbiont are to avoid being digested by the host and to replicate in its novel environment. Recent studies provide clues to how the precursors to mitochondria and the plastid overcame these challenges.