UPDATED - Cell - Horizontal Gene Transfer from Diverse Bacteria to an Insect Genome Enables a Tripar

Filip Husnik, Naruo Nikoh, Ryuichi Koga, Laura Ross, Rebecca P. Duncan, Manabu Fujie, Makiko Tanaka, Nori Satoh, Doris Bachtrog, Alex C.C. Wilson, Carol D. von Dohlen, Takema Fukatsu, John P. McCutcheon 2013: Horizontal Gene Transfer from Diverse Bacteria to an Insect Genome Enables a Tripartite Nested Mealybug Symbiosis. Cell 153: 1567-1578.
http://www.sciencedirect.com/science/article/pii/S0092867413006466
 
The paper has many comments, please see:

http://www.latimes.com/news/science/sciencenow/la-sci-sn-bugs-bacteria-20130621,0,1994908.story

http:// http://phenomena.nationalgeographic.com/2013/06/20/snug-as-a-bug-in-a-bug-in-a-bug/

https://www.simonsfoundation.org/features/science-news/tiny-genomes-may-offer-clues-to-first-plants-and-animals/