Eukaryotic Microbes (Protists) BIOL 1603 PDF

Eukaryotic Microbes (Protists) BIOL 1603  Protists, the most nutritionally diverse of all eukaryotes, include: – Photoautotrophs, which contain chloroplasts Chlorophylls a, b, c, and phycobilins – Heterotrophs, which absorb organic molecules or ingest larger food particles – Mi...

Eukaryotic Microbes (Protists) BIOL 1603  Protists, the most nutritionally diverse of all eukaryotes, include: – Photoautotrophs, which contain chloroplasts Chlorophylls a, b, c, and phycobilins – Heterotrophs, which absorb organic molecules or ingest larger food particles – Mixotrophs, which combine photosynthesis and heterotrophic nutrition Endosymbiosis in Eukaryotic Evolution Nuclear DNA (likely) arose from a lineage within the Archaea Mitochondria evolved by endosymbiosis of an aerobic prokaryote Plastids evolved by endosymbiosis of a photosynthetic cyanobacterium – There is now considerable evidence that at least some protist diversity is due to endosymbiosis Summary of putative events in the evolution of nucleus, mitochondria, and plastids. Lynn Margulis (1938-2011)  Secondary Plastid Endosymbiosis Endosymbiosis Plastid Primary  Kleptoplasty Elysia chlorotica The Sea Slug (phylum Mollusca) feeds by sucking the cell contents from algae. It keeps chloroplasts alive and functioning in its own body. http://www.seaslugforum.net/display.cfm?id=1969  Excavata Diplomonads Excavata Parabasalids Euglenozoans§ Dinoflagellates§ } Apicomplexans* Alveolates & Ciliates Diatoms X Stramenopiles Golden algae SAR Brown algae X Oomycetes X Rhizaria Chlorarachniophytes Rhizaria Forams Radiolarians Red algae Archaeplastida Chlorophytes Charophyceans Land plants Slime molds Gymnamoebas Unikonta Entamoebas Unikonta Nucleariids Fungi Choanoflagellates Animals  Protists (algae or protozoa) Storage Polysaccharide α-1,4 Glucan or β-1,3 Glucan Plastid Chlorophyll a, b, and/or c Phycobilins Plastid or pigments absent Cell Wall Cellulose, Silica, Protein or Absent Key Terms Mixotroph Chloropylls Serial Endosymbiosis Phycobilins Mitochondrion Cell Wall Chloroplast Polysaccharide Primary Endosymbiosis Glucan (glucose) Secondary Endosymbiosis Kleptoplasty  Diplomonads Parabasalids Kinetoplastids Euglenids  Euglenids (Excavata/Euglenozoa) Flagella 0.2 µm Euglena is a photoautotrophic unicell β-1,3 Glucan Plastid* Chlorophyll a Chlorophyll b Cell Wall Crystalline rod Protein pellicle Ring of microtubules *Derived by secondary endosymbiosis from a green alga Euglena Kinetoplastids (Excavata/Euglenozoa) Kinetoplastids have a single mitochondrion with an organized mass of DNA called a kinetoplast They include free-living consumers of prokaryotes in freshwater, marine, and moist terrestrial ecosystems This group includes Trypanosoma, which causes sleeping sickness in humans (Tsetse Fly) and Chagas’ disease (Reduviid or Triatomine Bug) 9 µm American Trypanosomiasis Key Terms Euglena Kinetoplast Contractile Vacuole Pellicle Eyespot Trypanosoma Chaga’s Disease Sleeping Sickness  Recent data suggest that the Alveolata, Stramenopiles and Rhizaria forms a monophyletic group—the SAR Alliance The evidence indicates that the Alveolata and Stramenopiles are sister groups that originated by a secondary endosymbiosis event The proposed endosymbiont is a red alga Diatoms Brown algae Dinoflagellates Diatoms Brown algae Dinoflagellates Diatoms (Stramenopila) Diatoms are unicellular algae with a unique two-part, glass- like wall of hydrated silica Diatoms usually reproduce asexually, and occasionally sexually  Diatoms (Stramenopila) Silica Cell Wall Triceratium is a photoautotrophic unicell β-1,3 Glucan Secondary plastid* Chlorophyll a Chlorophyll c Cell Wall Silica *Derived by secondary endosymbiosis from a red alga Fossil Diatoms Brown Algae (Stramenopila) Brown algae (Chl. a & c*) are the largest and most complex algae All are multicellular, and most are marine Brown algae include many species commonly called “seaweeds” and “kelps” Brown algae have the most complex multicellular anatomy of all algae *Plastids derived by secondary endosymbiosis from a red alga  Brown Algae (Stramenopila) Laminara is a multicellular photo- autotroph β-1,3 Glucan Secondary plastid* Chlorophyll a Chlorophyll c Cell Wall Cellulose  Dinoflagellates (Alveolates) Flagellum Alveoli Dinoflagellates are mostly photoautotrophic unicells α-1,4 Glucan Secondary Plastid* Alveolate Chlorophyll a Chlorophyll c 0.2 µm Cell Wall Cellulose *Derived by secondary endosymbiosis from a red alga  Dinoflagellates are A. …responsible for red tide “blooms” in the Gulf of Mexico (and elsewhere) B. …responsible for PSP (Paralytic Shellfish Poisoning) Apicomplexans (Alveolata) Apicomplexans are parasites of animals, and some cause serious human diseases One end, the apex, contains a complex of organelles specialized for penetrating a host They have a nonphotosynthetic plastid, the apicoplast Most have sexual and asexual stages that require two or more different host species for completion  The apicomplexan Plasmodium is the parasite that causes malaria Plasmodium requires both mosquitoes and humans to complete its life cycle More than 200 million people contracted malaria in 2019 More than 400,000 people died from malaria in 2019 Efforts are ongoing to develop vaccines that target this pathogen http://www.npr.org/blogs/health/2011/08/31/140069350/a-remnant-from-algae-in-malaria-parasite-may-prove-its-weakness  Apicomplexa (Alveolata) Plasmodium is a heterotrophic, unicellular parasite α-1,4 Glucan Apicoplast* No pigments! Cell Wall None *Derived by secondary endosymbiosis from a red alga Ciliates (Alveolata) Ciliates, a large varied group of protists, are named for their use of cilia to move and feed They have large macronuclei and small micronuclei (dikaryotic) The micronuclei function during conjugation, a sexual process that produces genetic variation Conjugation is separate from reproduction, which generally occurs by binary fission  Ciliates (Alveolata) Paramecium is a heterotrophic unicell α-1,4 Glucan Plastid None Cell Wall None  Ciliates (Alveolata) Paramecium is a heterotrophic unicell α-1,4 Glucan Plastid None Cell Wall None Key Terms Stramenopila Gametocyte Silica Alveolata Zygote Fossils Alveoli Ciliata Cellulose Dinoflagellate Paramecium Chlorophyll a Red Tide Macronuclei Chlorophyll c Plasmodium Micronuclei Sporozoite Dikaryotic Merozoite Diatom Diatoms Brown algae Dinoflagellates Rhizarians are a diverse group of protists defined by DNA similarities DNA evidence supports Rhizaria as a monophyletic clade (probably sister to Stramenopiles and Alveolates) Amoebas move and feed by filose (thread-like) pseudopodia; some but not all belong to the clade Rhizaria Rhizarians include forams and radiolarians Forams (Rhizaria) Foraminiferans, or forams, are named for porous, generally multichambered shells (mostly calcium carbonate), called tests Filose pseudopodia extend through the pores in the “test” Foram “tests” in marine sediments form an extensive fossil record  Forams (Rhizaria) 20 µm Fossil Foram Globigerina is a s heterotrophic unicell α-1,4 Glucan Plastid None Cell Wall None (CaCO3 shells) Filose Pseudopo dium Globigerina Amoebozoans Amoebozoans are amoeba that have lobe- or tube- shaped (lobose), rather than threadlike (filose), pseudopodia They include gymnamoebas, entamoebas, and slime molds Scientists are still debating about the relationship between Amoebozoans and Opisthokonts (animals and fungi) Gymnamoebas (Tubulinids/Amoebozoa) Gymnamoebas (Tubulinids) are common unicellular amoebozoans in soil as well as freshwater and marine environments Most gymnamoebas are heterotrophic and actively seek and consume bacteria and other protists  Entamoebae (Amoebozoa) Entamoeba histolytica is a heterotrophic, unicellular parasite α-1,4 Glucan Plastid None Cell Wall None Entamoebas are parasites of vertebrates and some invertebrates Entamoeba histolytica causes amoebic dysentery in humans Key Terms Rhizaria Lobose pseudopodia Foraminifera Gymnamoeba Filose pseudopodia Entamoeba Test Calcium carbonate Fossils Amoebozoa Red algae Green algae Land plants Red and green algae are the closest relatives of land plants Over a billion years ago, a heterotrophic protist acquired a cyanobacterial endosymbiont The photosynthetic descendants of this ancient protist evolved into red algae (red plants) and green algae (green plants). Land plants are descended from the green algae Archaeplastida is a supergroup used by some scientists and includes red algae, green algae, and land plants Red Algae (Archaeplastida) Red algae (Chl. a & phycobilins) are reddish in color due to an accessory (phycobilin) pigment, phycoerythrin, which masks the green of chlorophyll The color varies from greenish-red in shallow water to dark red or almost black in deep water Red algae are usually multicellular; the largest are seaweeds Red algae are the most abundant large algae in coastal waters of the tropics  Red Algae Bonnemaisonia and Palmaria are photoauto- trophic seaweeds α-1,4 Glucan Plastid Chlorophyll a Phycobilins Cell Wall Cellulose  Red Algae Porphyra (Nori) is an economically important photoautotrophic seaweed α-1,4 Glucan Plastid Chlorophyll a Phycobilins Cell Wall Cellulose Green Algae (Archaeplastida) Green algae (Chl. a & b) are named for their grass-green chloroplasts Plants are descended from the green algae The two main groups of green algae are Chlorophyta and Charophyta The Charophyta are the sister group to the land plants (Embryophytes) – aka the Streptophyta  Green Algae (Archaeplastida) Chlamydomonas is a photoauto- trophic unicell α-1,4 Glucan Plastid Chlorophyll a Chlorophyll b Cell Wall Cellulose Key Terms Archaeplastida Chlamydomonas Red Algae Zoospore Chlorophyll a Asexual Reproduction Phycobilin Fertilization Porphyra Meiosis Green Algae Charophyta Chlorophyll a, b Streptophyta Chlorophyta