3/3/2011

Protists

• Eukaryotes • Not a monophyletic group Protists – Paraphyletic

March 3rd, 2011 • Still use the term “protist” – All eukaryotes except Plants, Fungi, Animals

Protist Body Plans Protist Feeding Strategies

• Most unicellular • Photoautotrophs • Some colonial – Chloroplasts • Some multicelled • Heterotrophs • Mixotrophs • Blurry lines separating these – Can do photosynthesis and eat food – Different life stages can appear differently • Three feeding approaches have arisen independently multiple times

Protist Reproduction Endosymbiosis

• Very diverse • Mitochondria (proteobacteria) • Use all three ↓ • Chloroplasts (cyanobacteria) = plastids • Secondary endosymbiosis – One eukaryote phagocytized by another • Evidence: Nucleomorph (vestigial nucleus) Other reproductive strategies that don’t fit More membranes (up to 4)

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Protist Systematics

• Kingdom Protista abandoned • Some “protists” found to be fungi, plants, or animals • 5 “supergroups”

Present phylogeny is tentative, hypothetical, wrong – A lot left to learn

Excavata

• Linked by cytoskeletal morphology • Some have “excavated” feeding groove

• Three Groups – Diplomonads – Parabasalids – Euglenozoans

Excavata Excavata

• Diplomonads • Parabasalids – Lack Plastids – Lack Plastids – Modified Mitochondria (reduced) – Modified Mitochondria (reduced)

• No electron transport chain • No electron transport chain → H2 gas released • Mostly anaerobic environments • Mostly anaerobic environments Trichomonas vaginalis – 2 equal‐size nuclei and – Flagella multiple flagella – Many are parasites – Many are parasites

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Excavata Excavata

• Euglenozoans • Euglenozoans – Flagella have spiral or crystalline rod Kinetoplastids – Have single large mitochondrion Predators, photosynthesis, • Contains an organized mass of DNA parasites – Predators (prokaryotes) – Parasites (eukaryotes) – Kinetoplastids – Trypanosoma – Euglenids Surface proteins change

Excavata Chromalveolates

• Euglenozoans • Genetic Data suggests monophyly Euglenids • Secondary endosymbiosis of a red alga – Have one or two flagella Many mixotrophs • Controversial – Some lack plastids and have no plastid genes Two main groups – Alveolates and Stramenopiles

Chromalveolates Chromalveolates

• Alveolates • Alveolates – Monophyly well‐supported Dinoflagellates – Alveoli (membrane‐bound sacs) below plasma membrane – Cellulose plates for reinforcement • Unknown function – Two flagella in grooves – Dinoflagellates – Spin – Apicocomplexans – Auto‐, hetero‐, mixotrophs • Parasites – Blooms – Ciliates • Red tide (carotenoids) • Toxins

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Chromalveolates Chromalveolates

• Alveolates • Alveolates Apicocomplexans Apicocomplexans – Mostly parasites – Apex contains complex for burrowing into hosts – Retain modified plastid – Complex life cycles

– Plasmodium causes malaria

Chromalveolates Chromalveolates

• Alveolates • Alveolates Ciliates Ciliates – Video – Contain macronuclei and micronuclei

Chromalveolates Chromalveolates

• Stramenopiles • Stramenopiles – Marine algae Diatoms – Photoautotrophs and heterotrophs – Unicellular

– “Hairy” flagella – Wall of SiO2, overlap – Most reproduction asexual – Important marine and freshwater plankton – May use diatoms to fight global warming

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Chromalveolates Chromalveolates

• Stramenopiles • Stramenopiles Golden Algae Brown Algae – Yellow and brown carotenoids – Large (60m) and complex – Biflagellate – Multicellular – Photosynthetic, mixotrophic – Some specialized tissues – Most unicellular, some colonial – Thallus • Holdfast • Stipe • Blades

Chromalveolates Chromalveolates

• Stramenopiles • Stramenopiles Oomycetes Oomycetes – Previously classified as fungi • Hyphae – Cellulose cell walls • Chitin in fungi – No plastids – Decompose or parasitize – Phytophthora

Alternation of Generations

• Multicellular haploid and diploid stages – Heteromorphic or isomorphic

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