But this is pretty much the opposite of what we are learning about prokaryotic diversity.
prokaryote pro·kar·y·ote or pro·car·y·ote (prō-kār'ē-ōt')
An organism of the kingdom Prokaryotae, constituting the bacteria and cyanobacteria, characterized by the absence of a nuclear membrane and by DNA that is not organized into chromosomes.
Any of a wide variety of one-celled organisms of the kingdom Monera (or Prokaryota) that are the most primitive and ancient known forms of life. Prokaryotes lack a distinct cell nucleus and their DNA is not organized into chromosomes. They also lack the internal structures bound by membranes called organelles, such as mitochondria. At the molecular level, prokaryotes differ from eukaryotes in the structure of their lipids and of certain metabolic enzymes, and in how genes are expressed for protein synthesis. Prokaryotes reproduce asexually and include the bacteria and blue-green algae. Also called moneran. Compare eukaryote. See Table at taxonomy.