A nested set of bacterial endosymbionts within mealybug cells collectively provides amino acids to their host, but their genomes show that some pathways are distributed between both endosymbionts, while other essential proteins are missing altogether. The possibility that additional functions are shared between partners warrants comparisons with organelles.

This contribution details the complex history of early work by Boris Kozo-Polyansky (1924) that became available in English translation 86 years after it was published Russian. The great American naturalist Lynn Margulis—whose serial endosymbiosis theory presciently predated four decades—was instrumental organizing this resurrection and ‘horizontal transfer’ knowledge, forgotten time even Russia.

PLoS Biology | http://biology.plosjournals.org Symbiosis, an interdependent relationship between two species, is an important driver of evolutionary novelty and ecological diversity. Microbial symbionts in particular have been major evolutionary catalysts throughout the 4 billion years of life on earth and have largely shaped the evolution of complex organisms. Endosymbiosis is a specifi c type...

Photosynthesis in eukaryotes occurs in the plastid, an organelle that is derived from a single cyanobacterial primary endosymbiosis in the common ancestor of the supergroup Plantae (or Archaeplastida) that includes green, red, and glaucophyte algae and plants. However a variety of other phytoplankton such as the chlorophyll c-containing diatoms, dinoflagellates, and haptophytes contain a red al...