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A small phylum of single-celled freshwater algae whose primitive chloroplasts (cyanelles) resemble cyanobacteria. They are widely regarded as descendants of the most ancient lineage of photosynthetic eukaryotes, which evolved soon after the emergence of the ancestral primary photosynthetic eukaryote (the primary endosymbiont) through acquisition of a cynanobacterium as a permanent cell organelle (see endosymbiont theory). Notably, the cyanelles retain a trace layer of peptidoglycan, the characteristic cell wall material of eubacteria, between the inner and outer membranes. Like cyanobacteria and red algae, glaucophyte plastids contain phycobiliproteins as accessory pigments, and the thylakoids are not stacked, in contrast to their stacked arrangement in green algae and plants. Some members of the three genera are equipped with undulipodia and are motile.

Subjects: Biological Sciences.

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