Marek Mentel
Prednáška, Gymnázium GJH, marec 2012
Are eukaryotes all about oxygen?
...and what Earth history has to do with it?
Marek Mentel
Prednáška, Gymnázium GJH, marec 2012
Lecture content
• What are eukaryotes - eukaryotes specific features
• Eukaryotes origin theories
• Mitochondria types i.e. aerobic and anaerobic mitochondria
hydrogenosomes
mitosomes (cryptons)
• Energetic metabolism of individual mitochondria forms i.e. respiration
aerobic
anaerobic
fermentation
chemolithotrophy
• Mitochondria origin in the context of Earth geochemistry changes
Cytology - Prokaryotic & Eukaryotic cells comparison
Cytology - Eukaryotic cells specific features
Nucleus / EndoMembrane system / Golgi apparatus
Cytoskeleton / Flagella & Cilia
Endocytosis e.g. Phagocytosis
Mitosis
Sex – Meiosis & Fertilization
Mitochondria
Plastids
Peroxisome
Linear chromosomes (centromere, telomere, telomerase)
Spliceosome (spliceosomal Introns splicing - mRNA export coupling)
Habitats and Energetics - Prokaryotic & Eukaryotic
cells versatility comparison
aerobic respiration
anaerobic respiration
!! not true for eukaryotes !!
Eukaryotic cells origin theories review
Phagocytosis first / Mitochondria late view Mitochondria first / Phagocytosis late
view
Eukaryotic cells origin theories - prokaryotes within
prokaryotes plausibility
Mealybug Planococcus citri
endosymbiotic γ-proteobacteria
within ß-proteobacteria
Eukaryotic cells origin theories - ox-tox hypothesis
Eukaryotic cells origin theories - hydrogen hypothesis
Aerobic mitochondria
•
Biosynthetic pathways:
Heme synthesis
Fe-S synthesis
Ubiquinone synthesis
•
Metabolism:
Amino acids
Carbohydrates
Nucleotide
&
Lipid
•
Energetics:
Krebs cycle
aerobic respiration – oxidative phosphorylation
aerobic respiration
(facultative) Anaerobic mitochondria
• Unicellular protists & Metazoa:
Ciliates
nitrate, nitrite
Fungi
nitrate, nitrite, sulfur
Nematodes
fumarate
Plathelminths
fumarate
Snails
fumarate
Bivalves
fumarate
anaerobic respiration
Chemolithotrophic mitochondria
• Metazoa:
Bivalves
Polychaete worm
Crustaceans
chemolithotrophy – inorganic electron donor (S2-, HS-, H2S)
Hydrogenosomes and Mitosomes (Crypton) - MLOs
no energy metabolism
Mitosome
fermentation
– substrate-level phosphorylation
Hydrogenosome
• Unicellular anaerobes:
Parabasalids
(Trichomonas)
Ciliates
(Nyctotherus)
Chytridiomycete fungi
(Neocallimastix)
Amoeboflagellate
(Psalteriomonas)
Stramenopile
(Blastocystis)
Diplomonads
(Giardia)
Entamoebids
(Entamoeba)
Microsporidia
(Encephalitozoon)
Apicomplexan
(Cryptosporidium)
 Mitochondria, Hydrogenosomes, Mitosomes common features:
double membrane
protein targeting / import
iron-sulfur clusters synthesis
mitochondrial carrier family proteins
Hydrogenosomes and Mitosomes structure
hydrogenosome with cristae - N.ovalis
mitosome - Giardia
& Methanogen
mitochondria
& EReticulum
hydrogenosome without cristae
Neocallimastix patriciarum
mitosome - Cryptosporidium
(facultative) Anaerobic mitochondria – Fasciola hepatica
Anaerobic mitochondria / Hydrogenosome – Nyctotherus ovalis
Hydrogenosome – Piromyces sp. E2
Mitosome – Giardia intestinalis
Earth history - Geological TimeScales
eukaryotes origin
P - Pleistocene
Holocene
Geochemical history of Earth – atmosphere
oxygenation
eukaryotes origin
Earth history – significant lag in oceans oxygenation
& Canfield oceans chemistry
slight atmosphere oxygenation
continents weathering
sulfate-reducing bacteria radiation
Geochemical history of Earth – significant lag in
oceans oxygenation & Canfield oceans
eukaryotes origin
Anbar & Knoll, 2002
Earth history – significant lag in oceans oxygenation
& Canfield oceans
eukaryotes origin
Eukaryotic anaerobes & Proterozoic ocean chemistry
Dietrich, 2006
Mentel & Martin, 2008
Origins of mitochondria, hydrogenosomes and
mitosomes
Glycolysis - backbone of energy metabolism in Eukaryotes
Martin, 2001
Metabolically flexible mitochondria – Arenicola marina
Take home messages:
• Eukaryotes and Mitochondria
• Mitochondria:
O2
aerobic
oxidative phosphorylation
anaerobic
chemolithotrophic
hydrogenosomes – not uniform
mitosomes
• genome
• cristae
substrate-level
phosphorylation
no energy metabolism
• Anaerobic mitochondria & eukaryotic anaerobes make sense in
light of Proterozoic ocean chemistry
Obligate aerobes like ourselves seems to represent specialized
adaptation to recently oxygenated habitats
Take home messages:
• geochemical Earth history (changing Earth)
&
interconnection
Eukaryotes evolution
?
what makes mitochondria an essential compartment for eukaryotic cell –
where is the limit for its reduction
• not energy metabolism
- mitosomes
- cryptic mitochondria (Cryptosporidium parvum)
- mitosomes (Giardia intestinalis (syn. lamblia))
 iron-sulfur cluster biosynthesis
- cryptic mitochondria (Cryptosporidium parvum)
- mitochondria (yeast)