Why were archaea first classified as bacteria?

By the 1960s, many prominent microbiologists, such as Roger Stanier, declared the problem of bacterial classification hopeless. read more

But what surprised everyone - and what many biologists still have trouble accepting - was that the extremophiles were no more closely related to temperate bacteria than they are to eukaryotes (plants, animals, fungi and protists). read more

Archaea were initially classified as bacteria, receiving the name archaebacteria (in the Archaebacteria kingdom), but this classification is outdated. Archaeal cells have unique properties separating them from the other two domains of life, Bacteria and Eukarya. read more

But by the 1970s phylogeny becoming based on the sequence of DNA and RNA which were just becoming more available. Based on a simple comparison of the sequences of 18S rRNA of 13 fungi, bacteria and archaea, Woese and Fox showed that the bacteria and the archaea were about as different from the eukaryotes than from the bacteria. (see table 1). read more