The Language of Symbiosis

PART 1 — Climbing Up and Down the Tree

The Monster with More Than Five Genomes

Symbiosis in the Cell and the Insight of Lynn Margulis: The biologist Lynn Margulis saw the basic principle of life not as competition and predation but as symbiotic partnership. Mitochondria, which act as batteries producing energy inside the cell, and chloroplasts, the photosynthetic organs of plants, are the result of independent bacteria that were absorbed by ancient cells and, over the course of evolution, became one with their hosts. Mitochondria are inherited not from both parents but only through the mother's egg, and through this mode of inheritance they have been passed down to our ancestors for more than a billion years.

The Darwin Termite and the World of Multiple Genomes: In the gut of the Darwin termite, which lives only in Australia, lives a protist called Mixotricha paradoxa that helps break down the wood fiber through its metabolism. This protist is not a single organism either. Countless spirochete bacteria cling to its surface like cilia, propelling it and coordinating with remarkable precision to the protist's signals; add the Bacteroides-type bacteria that serve as a supporting structure, along with the bacteria inside, and the number of genomes climbs well past eight.