L. Margulis, ARCHAEAL-EUBACTERIAL MERGERS IN THE ORIGIN OF EUKARYA - PHYLOGENETIC CLASSIFICATION OF LIFE, Proceedings of the National Academy of Sciences of the United Statesof America, 93(3), 1996, pp. 1071-1076
A symbiosis-based phylogeny leads to a consistent, useful classificati
on system for all life, ''Kingdoms'' and ''Domains'' are replaced by b
iological names for the most inclusive taxa: Prokarya (bacteria) and E
ukarya (symbiosis-derived nucleated organisms), The earliest Eukarya,
anaerobic mastigotes, hypothetically originated from permanent whole-c
ell fusion between members of Archaea (e.g., Thermoplasma-like organis
ms) and of Eubacteria (e.g., Spirochaeta-like organisms). Molecular bi
ology, life-history, and fossil record evidence support the reunificat
ion of bacteria as Prokarya while subdividing Eukarya into uniquely de
fined subtaxa: Protoctista, Animalia, Fungi, and Plantae.