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Origin of Eukaryotic Organelles
Cyanobacterium
endosymbiosis
Extinct
Original Cell
Kingdom
Protista
Eubacterium
endosymbiosis
Though sketched here as single
events, these endosymbioses were
very likely multiple events!
http://www.stockhillhouse.co.uk/griffon.jpg
Extant
Archezoans
•
“Protozoan parasites without mitochondria or Golgi”
•
Oldest nucleated cells

Diverged from other Eukaryotes 2bybp…
prior to ER and Golgi evolution

Lack peroxisomes

Ribosomes are 70S but NOT 80S
•
400 species (many more likely unknown parasites!)
•
Three phyla:
1.
Archaeamoebae/Pelobiontida (Pelomyxa)
2.
3.
Metamonada (Giardia)
Microsporidia
Pseudopodia Endosymbiotic
Pelomyxa palustris
bacteria
Free-living in freshwater
sediment (microaerophilic)
Phagocytosis active
Accumulate glycogen
reserves
At least 3 species of
endosymbiont in each
cell…two species are
methanogenic
archaeons!
Anterior uroid
(macropseudopodium)
for amoeboid movement
Uroid
Glycogen body
Vacuoles
http://www.btinternet.com/~stephen.durr/pelomyxapalustris.html
Smaller pseudopodia do
not enlarge
Reproduction:
Mitosis of nucleus
Cytokinesis by furrowing
Nuclei
“Daughter” Amoeba
http://www.btinternet.com/~stephen.d
urr/pelomyxapalustris.html
What would you suggest has
been a large component of this
individual’s phagocytosis diet?
http://www.microscopyuk.org.uk/micropolitan/fresh/protozoa/frame3.html
Trichonympha
Termite gut protist
symbiont lacking
mitochondria
Protist has bacterial
endosymbionts making
cellulase for digesting
nucleus wood particles taken in
by phagocytosis
spirochetes
wood
particles
and
bacteria
http://www.microscopy-uk.org.uk/mag/imgmar03/Trichonympha755.jpg
And spirochete
ectosymbionts for
motility
Figure 7-00 Page 119
microfilaments
nucleus
microtubules
A TEM cross section of a cilium of a protist.
It shows the basic structure of all eukaryotic flagella…
There are nine doublets of microtubules surrounding one pair.
They are contained in cell membrane and surrounded by cytosol.
The interaction of calcium,
ATP and the proteins
associated with the
microtubules permit the
microtubules to flexibly
interact resulting in flagellar or
ciliary motion.
The flexible eukaryotic
flagellum made of tubulin is
sometimes called an
undulipodium.
http://cellbio.utmb.edu/cellbio/cilia7.jpg
Flagella are found in Protista
Chromista and Animalia, but
not in Rhodophyta, higher
Plantae or Fungi.