Archaea: Narrowing the gap between prokaryotes and eukaryotes

摘要

In the last 30 years, our views on the nature of the relationship between prokaryotes and eukaryotes have come full circle. In the 1960s we believed, with Sta-nier and van Niel, that the line of demarcation between bacteria (including cya-nobacteria) and other cellular organisms was Life's "largest and most profound single evolutionary dichotomy" (1). This line was crossed only once, by the pro-karyote which first constructed a rudimentary membrane around its genome and cobbled together the first rudimentary cytoskeleton, an entity we used to call the proto-eukaryote. Whether we endorsed the then newly resurgent endosymbiont hypothesis for the origins of mitochondria and chloroplasts or envisioned a gentler prokaryote-to-eukaryote (cyanobacterium-to-"uralga") transition, we had to believe that there was once such a bridging organism, whose genome gave rise to the nuclear genome of eukaryotes (2).