Microbiology. Modern symbionts inside cells mimic organelle evolution.
Some 2 billion years ago, primitive cells took in free-living microbial guests that gave rise to the organelles called mitochondria and chloroplasts. Those momentous events, investigators are realizing, were not one-of-a-kind. Endosymbiosis, as a mutually beneficial relationship between an organism and a guest living inside its cells is called, is alive and well today, and has lessons to offer for how the process played out early in life history. At a meeting, biologists described how they are exploring those parallels. Cicada endosymbiont genomes have expanded and fragmented, creating genomic insanity, much like some plant mitochondrial genomes. And the complexity of the evolution of the chloroplast was highlighted with a discussion of single-cell aquatic protists called dinoflagellates that have taken in an alga called a diatom.