From Garry Marley, Stillwater, Oklahoma, US
It was interesting to learn of a suspected archaeal host responsible for its primal symbiosis with an aerobic bacterium. The theory of endosymbiosis for eukaryotic cell origins, controversially proposed by Lynn Margulis in 1967, now has ample support with the detection of complex nucleic acids and protein synthesis within today’s mitochondria and chloroplasts(17 May, p 8).
Plant cells then got a double whammy of “modular evolution” when a proto-eukaryote, already with aerobic bacteria, subsequently acquired photosynthetic bacteria via endosymbiosis. Their putative descendants – the chloroplasts – have DNA homology with modern cyanobacteria (“blue-green algae”). We must, therefore, humbly conclude that the eukaryotic plant cell has an evolutionary “one-up” on those of us composed merely of animal cells.
