protist tour

• Cryptophytes(Cryptomonads):algae with secondary plastids of red algal origin Plastid has NUCLEOMORPH, remnant nucleus with red algal genes!
• Amoebazoans:

  • Unicellular organisms forming broad, tubelike lobes (pseudopodia)
  • Actin/myosin are fundamental to amoeboid movement
• Entamoebas:

  • Symbiotic parasites
  • Genus Entamoeba includes several human parasites, with E. histolytica causing amoebic dysentery
  • Feed on intestinal bacterial and host tissue materials
  • About 35-50 million people infected, killing >55,000 per year
  • Transmission associated with poor sanitary conditions
  • Entamoeba histolytica ingests erythrocytes
• Tubulinids:

  • Diverse heterotrophs that prey upon bacteria and other protists in soil, freshwater, and marine habitats
  • Engulf prey with pseudopodia
• Slime Molds:

  • Form macroscopic motile amoeboid structures and spore-producing fruiting bodies
  • Feed on bacteria and other microorganisms
  • Two different groups:

  1. Myxomycetes (Myxogastria) - plasmodial slime molds

  2. Dictyostelids - cellular slime molds
• Myxomycetes (Myxogastria) - Plasmodial Slime Molds:

  • Haploid spores germinate to produce myxamoebae or myxoflagellates
  • Compatible amoebae fuse to form a zygote that undergoes mitoses without cytokinesis, producing a large, mobile, diploid multinucleate but unicellular plasmodium
  • Plasmodium feeds by engulfing bacteria and other microorganisms
  • When sufficient resources acquired, the plasmodium settles and forms fruiting bodies
  • Nuclei undergo meiosis to produce haploid spores
• Dictyostelids (Cellular Slime Molds):

  • Haploid spores germinate to produce amoebae that feed and divide
  • When food supply is depleted, amoebae secrete cAMP to attract others and form a multicellular pseudoplasmodium (slug) that migrates and forms fruiting bodies with spores
• Sex in Some Dictyostelids:

  • Amoebae fuse as gametes to form a binucleate cell, which enlarges into a giant cell
  • Attracts other amoebae with cAMP signal, nuclei fuse to form a zygote
  • The diploid giant cell ingests and digests attracted amoebae, forming a resting macrocyst
  • Meiosis followed by many mitoses produces many haploid amoebae when the macrocyst germinates
• Protostelids:

  • Spore germinates to produce haploid cells with flagella
  • Cells may fuse as gametes or become feeding amoebae
  • Form tiny stalked fruiting bodies with single or few spores
  • Ceratiomyxa produces larger, macroscopic fruiting bodies
• Excavata:

  • Mostly heterotrophic unicellular flagellates
  • Includes human parasites like Giardia, Trichomonas vaginalis, and Naegleria
  • Giardia is a human intestinal parasite with highly reduced mitochondria
  • Trichomonas vaginalis is a human genital parasite, sexually transmitted
  • Naegleria, a percolozoan, is known as the "brain-eating amoeba" and can cause rare infections in the human CNS
• Euglenozoans:

  • Include kinetoplastids like Trypanosoma causing African sleeping sickness, Chagas's disease, and Leishmania causing Leishmaniasis
  • Euglenids include algae and trypanosomes in blood samples
• Discobids (Discicristata):

  • Have disc-shaped mitochondrial cristae
• Euglenids:

  • Common in wetlands with decaying organic matter
  • Contain chlorophyll a, chlorophyll b, carotenoids, and eyespot
  • Some have a secondary plastid of green algal origin with 3 membranes
  • Some are myxotrophic, being photosynthetic and heterotrophic/phagotrophic
  • Have 2 anterior flagella, with only one emerging
• Photosynthetic euglenids often also heterotrophic/phagotrophic
• Euglenids have a flexible pellicle of proteinaceous strips on the inner side of the plasmalemma
• Cryptophytes (Cryptomonads) are algae with secondary plastids of red algal origin
• The photosynthetic euglenids have secondary plastids of green algal origin
• Euglenids have two anterior flagella, with only one emergent
• Cryptophytes have unique organelles called ejectosomes: spiral ribbons under tension
• Haptophytes are algae with secondary plastids of red algal origin; carotenoid fucoxanthin is an accessory pigment
• Most haptophytes have a special organelle called the haptonema, which resembles a flagellum but cannot beat
• Haptophytes include "Coccolithophorids" that have ornamented CaCO3 scales
• Haptophytes are important planktonic primary producers at the base of the food chain
• Centrohelids are spherical heterotrophic unicells with narrow cellular projections (axopods) supported with microtubules
• Centrohelids like Acanthocystis have endosymbiotic green algae of the genus Chlorella
• Foraminiferans are mostly marine heterotrophs that secrete chambered shells (tests) of CaCO3 to the interior of the membrane
• Cercozoans include algae with secondary plastids of green algal origin (Chlorarachniophytes) and primary plastids of cyanobacterial origin independent of all other plastids
• Contemporary cyanobacterium most closely related to the source of all other plastids is freshwater Gloeomargarita lithophora
• Contemporary cyanobacterium most closely related to the source of Paulinella's plastid is marine planktonic Synechococcus
• The two cyanobacteria are very distantly related
• Protists are a paraphyletic group within the Eukarya domain
• Most protists are unicellular, but some are colonial and multicellular
• Protists include all modes of nutrition: photoautotrophs, heterotrophs, and mixotrophs
• There are four supergroups of Eukaryotes, each with several protists
• Excavata (Supergroup) includes:

  • Diplomonads
  • Parabasalids
  • Euglenozoans
• S.A.R (Supergroup) includes:

  • Stramenopiles (Clade) with Diatoms and Brown Algae
  • Alveolates (Clade) with Dinoflagellates, Apiromplexans, and Ciliates
  • Rhizarians (Clade) with Radiolarians
• Archaeplastida (Supergroup) includes:

  • Red Algae
  • Green Algae
• Unikonta (Supergroup) includes:

  • Amoebozoans (Clade) with Slime Molds and Entamoebloas
  • Ophisthokonts (Clade)
• Excavata (Supergroup) characteristics:

  • Cytoskeleton and presence of flagella
  • Some members have an "excavated" feeding groove
• Diplomonads:

  • Lack plastids and have reduced mitochondria (mitosomes)
  • Two nuclei and 8 flagella