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#biological classification

123 public questions tagged with this topic.

Microbial Physiology

Which scientist introduced the three-domain system based on 16S rRNA sequencing?

Prior to molecular phylogeny, life was divided into five kingdoms based on morphology, staining, and physiology. Carl Woese revolutionized classification in late 1970s by utilizing chronometer molecules that evolve slowly and are universally distributed, specifically 16S ribosomal RNA for prokaryotes and 18S rRNA for eukaryotes. By comparing oligonucleotide catalogs and later full sequences, he uncovered that methanogens and other extremophiles formed lineage as divergent from typical bacteria as bacteria were from eukaryotes. This led to proposal of three primary domains: Bacteria, Archaea, a

Ref: Woese et al., PNAS 1990, Towards a Natural System; Sapp, Microbe 2007, The Three-Domain System.

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Microbial Physiology

Which domain of life do Archaea belong to?

Archaea represent a distinct domain of life alongside Bacteria and Eukarya, established by Carl Woese through comparative analysis of 16S ribosomal RNA sequences. Morphologically they resemble bacteria as prokaryotes lacking membrane-bound nucleus, typically possessing circular chromosomes and 70S-like ribosomes, yet they exhibit unique molecular features in transcription, translation, and membrane composition that separate them from true bacteria. For educational simplification, archaea are often grouped under broad term prokaryotes to contrast with eukaryotes that contain nuclear envelope, l

Ref: Woese & Fox, PNAS 1977, Phylogenetic Structure of Prokaryotes; Madigan et al., Brock Biology, Archaea Domain.

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