Paulinella

Paulinella chromatophoraPaulinellidae
Paulinella is a genus of about nine species of freshwater amoeboids.wikipedia
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Chloroplast

chloroplastschloroplast stromaplastoglobuli
This is striking because the chloroplasts of all other known photosynthetic eukaryotes derive ultimately from a single cyanobacterium endosymbiont, which was taken in probably over a billion years ago by an ancestral archaeplastidan (and subsequently adopted into other eukaryote groups, by further endosymbiosis events).
With one exception (the amoeboid Paulinella chromatophora), all chloroplasts can probably be traced back to a single endosymbiotic event, when a cyanobacterium was engulfed by the eukaryote.

Archaeplastida

archaeplastidangreen and red algaePrimoplantae
This is striking because the chloroplasts of all other known photosynthetic eukaryotes derive ultimately from a single cyanobacterium endosymbiont, which was taken in probably over a billion years ago by an ancestral archaeplastidan (and subsequently adopted into other eukaryote groups, by further endosymbiosis events).
In all other groups besides the amoeboid Paulinella chromatophora, the chloroplasts are surrounded by three or four membranes, suggesting they were acquired secondarily from red or green algae.

Cyanobacteria

blue-green algaecyanobacteriumblue green algae
longichromatophora'', the first two being freshwater forms and the third a marine form, which has recently (in evolutionary terms) taken on a cyanobacterium as an endosymbiont.
The fact that another independent and more recent primary endosymbiosis event has been described between a cyanobacterium and a separate eukaryote lineage (the rhizarian Paulinella chromatophora) also gives credibility to the endosymbiotic origin of the plastid.

Amoeba

amoeboidamoebaeSarcodina
Paulinella is a genus of about nine species of freshwater amoeboids.

Endosymbiont

endosymbioticendosymbiosisendosymbionts
longichromatophora'', the first two being freshwater forms and the third a marine form, which has recently (in evolutionary terms) taken on a cyanobacterium as an endosymbiont.
Paulinella chromatophora is a freshwater amoeboid which has recently (evolutionarily speaking) taken on a cyanobacterium as an endosymbiont.

Robert Lauterborn

Lauterborn
He described the genus Paulinella (named after his step-mother).

Eukaryote

Eukaryotaeukaryoticeukaryotes
This is striking because the chloroplasts of all other known photosynthetic eukaryotes derive ultimately from a single cyanobacterium endosymbiont, which was taken in probably over a billion years ago by an ancestral archaeplastidan (and subsequently adopted into other eukaryote groups, by further endosymbiosis events).

Prochlorococcus

Prochlorococcus marinus
chromatophora symbiont was related to the Prochlorococcus and Synechococcus'' cyanobacteria (sister to the group consisting of the living members of those two genera).

Synechococcus

S. elongatusSynechococcus elongatuselongatus
chromatophora symbiont was related to the Prochlorococcus and Synechococcus'' cyanobacteria (sister to the group consisting of the living members of those two genera).

Muller's ratchet

accumulationMueller's ratchetMüller’s ratchet
Other genes have degenerated due to Muller's ratchet - accumulations of harmful mutations due to genetic isolation, and have probably been replaced with genes from other microbes through horizontal gene transfer.

Horizontal gene transfer

lateral gene transferhorizontal transfergene transfer
Other genes have degenerated due to Muller's ratchet - accumulations of harmful mutations due to genetic isolation, and have probably been replaced with genes from other microbes through horizontal gene transfer.

Heterotroph

heterotrophicheterotrophsheterotrophy
chromatophora (those regions not modified by the symbiont) are most closely related to the heterotrophic P.

Rhizaria

chlorarachneansRhizarians
Except from the Chlorarachniophyte and three species in the genus Paulinella in the phylum Cercozoa, they are all non-photosyntethic, but many foraminifers have a symbiotic relationship with unicellular algae.

Monadofilosa

SarcomonadeaBodomorphaProleptomonas
It has also been described as Sarcomonadea (Cercomonas, Heteromita, Bodomorpha, Proleptomonas, Allantion), Thecofilosea (Cryptodifflugia, Cryothecomonas), Spongomonadea (Spongomonas, Rhipidodendron), and Imbricatea (Thaumatomonas, Thaumatomastix, Allas, Gyromitus, Euglypha, Trinema, Paulinella).

Symbiogenesis

endosymbiotic theorysecondary endosymbiosisendosymbiotic
Using the example of the freshwater amoeboid, however, Paulinella chromatophora, which contains chromatophores found to be evolved from cyanobacteria, Keeling and Archibald argue that this is not the only possible criterion; another is that the host cell has assumed control of the regulation of the former endosymbiont's division, thereby synchronizing it with the cell's own division.

Protist

ProtistaprotistsProtoctista
For example, Paramecium bursaria and Paulinella have captured a green alga (Zoochlorella) and a cyanobacterium respectively that act as replacements for chloroplast.

Testate amoebae

testate amoebatestateshell-bearing amoeboids

Photosynthesis

photosyntheticphotosynthesizephotosynthesizing

Gloeomargarita lithophora

Gloeomargarita
A similar endosymbiotic event occurred about 500 million years ago, with another Synechococcus related bacteria appearing in Paulinella chromatophora.

Michael Melkonian

Melkonian
The cercozoan photosynthetic amoeba Paulinella chromatophora was discovered as an example for the evolution of photosynthetic organelles through a second primary endosymbiosis independent of the origin of plastids.

List of sequenced plastomes

complete chloroplast genomehundreds of chloroplast DNAs
The unicellular eukaryote Paulinella chromatophora possesses an organelle (the cyanelle) which represents an independent case of the acquisition of photosynthesis by cyanobacterial endosymbiosis.

Plastid

plastidsproplastidproplastids
Paulinella has a similar organelle which does not belong to the plastids discussed in this text.