What is a prokaryote? Does anyone really know? In this article from Microbiology Today Norman Pace says not, and believes that the term has stuck since it was first coined in the late 19th century, but with no scientific foundation. He would like all microbiologists to join him in scrapping this anachronism in modern biology:
Experimental results rarely upset the common wisdom of a scientific discipline, but that happened to biology late in the 20th century. The common wisdom in deep evolution and how we classify organisms was rendered sorely in need of modernization. And that modern-ization is happening too slowly. The anachronism here is the notion of “prokaryote” and the model of biological organization and evolution that it elicits. This model, which I term the “prokaryote–eukaryote” model, posits that fundamentally there are two kinds of organisms, prokaryotes and eukaryotes, defined by the presence or absence of a nucleus (more properly nuclear membrane). Additionally, the model proposes that prokaryotes gave rise to eukaryotes, as shown in the figure overleaf. The problem, however, is that the prokaryote concept has been undermined critically by sequence-based phylogenetic results. Indeed, the notion of prokaryote was scientifically illogical from the beginning because the definition, an “organism without a nucleus”, is a negative definition. No-one can tell you what a prokaryote is, they can only tell you what it is not. Yet, institutional biology embraced the notion of prokaryote and it came to dominate textbooks, journals and discourse in matters of deep evolution. But the hypothesis of the prokaryote was never tested…
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