The theory that the nucleus of eukaryotes arose by capture of a guest prokaryote by an engulfing host prokaryote. Thus the inner nuclear membrane would originally be the guest's plasma membrane and the outer nuclear membrane would be the invaginated host's cell membrane. Phylogenetic studies of translation elongation factors (q.v.) suggest that the eukaryotic nucleus arose from a guest bacterium similar to an eocyte, one of the sulfur-dependent thermophiles (q.v.). See Classification, Archaea Crenarchaeota; Chronology, 1992, Rivera and Lake; endosymbiont theory.
Subjects: Genetics and Genomics.