Glaucophyte

A glaucophyte is a freshwater alga in a small lineage of Archaeplastida. Its plastids retain a peptidoglycan wall and other features linking them to cyanobacteria.

Plastid: A DNA-containing organelle in eukaryotic cells, including chloroplasts and related structures. Glaucophyte photosynthesis takes place in plastids with unusually bacteria-like traits.
Cyanelles: The plastids of glaucophytes, retaining features such as a peptidoglycan wall. This specialized plastid is the defining cellular structure of glaucophytes.
Cyanophora paradoxa: A unicellular glaucophyte commonly studied for its cyanelles and cellular biology. Its well-characterized cyanelles make it a leading model for glaucophyte plastid research.
Red algae: A lineage of mostly aquatic photosynthetic eukaryotes characterized by red algal pigments. Red algae share ancient primary plastid ancestry with glaucophytes but lack their plastid peptidoglycan wall.
Primary endosymbiosis: The evolutionary incorporation of a cyanobacterium into a eukaryotic cell, giving rise to primary plastids. It explains how glaucophytes acquired plastids from a cyanobacterial ancestor.
Chlorophyll a: A photosynthetic pigment that absorbs light and drives oxygen-producing photosynthesis. Glaucophyte plastids use chlorophyll a to capture light.
Glaucocystis nostochinearum: A freshwater glaucophyte with a cell wall and blue-green plastids. Its conspicuous plastids illustrate the cyanobacterial features retained by glaucophytes.
Green algae: A diverse lineage of photosynthetic eukaryotes related to land plants. Green algae share Archaeplastida ancestry with glaucophytes but have plastids with a different suite of traits.
Cyanobacteria: A group of bacteria that perform oxygen-producing photosynthesis. Glaucophyte plastids descend from a cyanobacterium and retain signs of that ancestry.
Phycobilisome: A light-harvesting complex of pigments and proteins found in cyanobacteria and some algae. Glaucophyte plastids retain phycobilisomes, a trait shared with cyanobacteria and red algae.

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Endosymbiotic theoryRelated: Their plastids preserve peptidoglycan between membranes, an unusual clue to plastid origins.