BIO2017: Lecture 2

Traditional grouping of eukaryote microbes

Protists/Protozoa 

• Flagellates
• Amoebae- including Radiolarans and Heliozoans- protoplasmic
• Ciliates- short stiff ciliary hairs all over their surface

Fungi

• True fungi (non-motile except for uniflagellate chytrids)
• Biflagellate zoosporic 'fungi'- oomyctes, hyphochytrids, labyrinthulids

Eukaryote Algae 

In 19th century- plant and animals were divided as the 2 major kingdoms

Ernst Hackel was one of first to recognise a more complex tree of life- first to realise that protists were just as diverse as plants and animals

one of first accounts of how kingdom organisation should be made was by Copland in 1930's, this was developed by Robert Whittaker- kingdom division was based on nutritional mode

• plants- autotrophic
• animals- heterotrophic
• fungi- osmotrophic
• Protista- phagotrophic

something about protist biology stops them from evolving into multicellular organisms, you need eukaryotic cell organisation

Margulis pioneered idea that eukaryotic cells evolved through endosymbiosis- also proposed that nucleus and eukaryote cilium/flagellum, but evidence is poor.

prokaryote must have lost cell wall in order to be engulfed- became amoeboid, no example today of amoeboid prokaryote- there were ancestral species like this but they are extinct

mitochondria and chloroplasts contain their own genomes, have genes that code for ribosomes

David Patterson and Mitch Sogin were responsible for getting many eukaryotic mictochondrial genes sequenced 

in 1990 Carl Woese came up with 3 domains concept for prokaryotes:

• Bacteria
• Archaea- often occurred in extreme environments- people assumed they were primative because they could have evolved during the less hospitable periods of the earth's history 
• Eukarya 

this was based on 16s gene

In eucarya- there were some early diverging clades- organisms that evolved early- mostly parasites- they were mostly anaerobic- you would expect this from primitive organisms- didn't appear to have any typical mitochondria. Do these represent primitive eukaryotes that never acquired mitochondria by endosymbiosis?

In mid 1980s these were grouped as archezoa by Tom Cavalier- this is called Archezoa hypothesis i.e. primitively amitochondriate eukaryotes 

Archezoa:

• Giardia- cause nasty dissentry 
• Trichomonas- causes STD vaginalius- live in vagina
• Microsporidians- particularly pathogenic to invertebrate- can attack vertebrates- can infect immuno compromised mammals
• Entamoeba- gut parasites caue chronic dissentry

Archezoa- frequently internal parasites so often live in anaerobic conditions

By time Archezoan hypothesis was gathering momentum- getting…