PROTISTS OUTLINE Endosymbiosis Chapter 27 Classifying Protists General Biology of Protists End of Section 1 Some Lineages: Exam 1 next week 1. Diatoms (glass walls) (Friday, 28 Feb 14) 2. Dinoflagellates, Ciliates, Apicoplasts (Alveolata) 3. Heterokonts (Stramenopiles)– Golden-brown algae, Brown algae) 4. Red algae (Rhodophyta) 5. Green algae (Chlorophyta ) 6. Euglenoid algae (Euglenophyta ) Volvox 7. Collared Flagellates (Choanoflagellates) PS Protist
CLASSIFYING PROTISTS CURRENT PROTIST CLASSIFICATION
Recall the endosymbiotic origin of organelles Chlorophyll types (a,b,c) where present: (Margulis, U Mass Amherst) a,b a,b a,c a a,b Protists are the most diverse of the four kingdoms in the domain Eukarya. Polyphyletic! • artificial “group of convenience” Kingdoms derived PROCARYOTES EUKARYOTES • mainly single-celled organisms from Protists • wide diversity of nutrition (comparable to bacteria) Most are photosynthetic • little agreement about classification Non-photosynthetic • good molecular classification may not happen (HGT) Polyphyletic. Includes amoebae, flagellates and ciliates.
GENERAL BIOLOGY OF THE PROTISTS Motility in protists Locomotor organelles 1. Passive movement in fluids – air and water Complex flagella and cilia – 11 bundled microtubules Powered by ATP – similar to archaea flagella 2 and 3. Flagella and cilia 4. Pseudopods [bacterial flagella use protons (H+) as fuel] Pseudopods (the amoeboid protists) Cysts (spores ) – dormant form of a cell with resistant outer covering Outer wall protects organisms Large variety, including proteins, glycoproteins, cellulose, silica, calcium, or naked cell membrane) ‘9+2’ arrangement of contractile Pseudopods enable ‘amoeboid Some have scales and spines for protection microtubules powered by ATP movement using sol-gel conversion of cytoplasm
1 GENERAL BIOLOGY OF THE PROTISTS GENERAL BIOLOGY OF THE PROTISTS Reproduction • Typically asexual Nutrition • binary fission - equal halves (as in procaryotes) Same as bacteria (except no chemotrophy) • budding - progeny cell grows from “bud” • phototrophs • schizogony - multiple fission (>2 daughter cells) • heterotrophs • Sexual reproduction in times of stress • phagotrophs – ingest particles across cell • Quorum sensing – ‘awareness of other cells’ membrane or ‘mouth’ (oral cavity) through chemical sensing. • organotrophs – absorb organic solutes Originally applied to bacteria, now to many protists Can trigger change from asexual to sexual reproduction
Eukaryote Life Cycles – 3 basic types GROUP 1. D IATOMS •Diatoms – live in glass ‘houses’ (silica outer wall) •Photosynthetic (Chl a,c) – unicellular organisms with PROTISTS PLANTS, FUNGI chloroplasts and walls of silica (‘shells’ or ‘frustules’) or seeds •Habitat: Marine, estuarine, and freshwater Dominant form: 1N Dominant forms: 1N + 2n alternate •Account for ~ 50% of global photosynthesis!!!
(false color) ANIMALS
Dominant form: 2N No flagella (except gametes of a few centrics)
GROUP 2. ALVEOLATA GROUP 2. ALVEOLATA (DINOFLAGELLATES , APICOMPLEXES , C ILIATES ) (DINOFLAGELLATES , APICOMPLEXES , C ILIATES )
Dinoflagellates – Chlorophyll a,c Apicomplexes – unicellular osmotrophs Distinctive biochemistry, flagella, and heavy cellulose coats • insect parasites are injected into mammals by mosquitoes responsible for marine toxic “red tides” • amoeboid with an “apical complex” group of organelles Many radiate bioluminescence (diel cycle, glow at night) that aid in penetrating cells of “victims” paralytic shellfish poisoning Plasmodium * -- genus of malarial parasite in humans Attempts at malaria eradication: • eliminating mosquitoes (limited success) • poisoning Plasmodium inside the human host has resulted in resistance to drugs (e.g. to quinine) • NEW THERAPY: Vaccines containing Plasmodium proteins activate immune system antibodies
*NOTE: See a second meaning of “plasmodium” – Slide 34) Amphidinium
2 GROUP 2. ALVEOLATA GROUP 2. ALVEOLATA (DINOFLAGELLATES , APICOMPLEXES , CILIATES ) (DINOFLAGELLATES , APICOMPLEXES , CILIATES )
Ciliates –Unicells that ingest bacteria (phagocytosis ) Paramecium (a ciliate) Cilia and flagella are structurally identical (9+2) Most have large numbers of cilia for locomotion
• form vacuoles to digest food
• contractile vacuoles regulate water balance Example: Paramecium (next slide)
Paramecium dividing
MORE EXAMPLES OF CILIATES STRUCTURE OF CILIA
cilia
A free-living ciliate with A ciliate with a contractile ‘9+2’ arrangement of protein cilia covering its cell stalk, attached to substrate microtubules is the same as in flagella (False color) Clusters of cilia
GROUP 3. STRAMENOPILA –FLAGELLA WITH HAIRS FLAGELLA OF STRAMENOPILA (G OLDEN -BROWN ALGAE , B ROWN ALGAE , AND OOMYCETES ) Stramenopila –“straw hairs” referring to “hairs” on one of the two unequal flagella) some are photosynthetic with chlorophylls a and c golden-brown algae – microscopic, photosynthetic brown algae – large brown seaweeds photosynthetic with alternation of generations (sporophytes and gametophytes) oomycetes – water molds – no chlorophyll, decomposers (organotrophs) Two different types of flagella, one with “straw hairs”
3 BROWN ALGAE GOLDEN -BROWN ALGAE (MICROSCOPIC ) GIANT KELPS –UP TO 328 FT (100 M) THE LONGEST PHOTOSYNTHETIC ORGANISMS !
Cell diameter ~ 10 µM Silica scale (~2 µM long)
Some golden-brown algae have a silica “armor” of scales and spines attached to the outside of the cell membrane
OOMYCETES (DECOMPOSERS ) GROUP 4. RHODOPHYTA
Red algae range in size from microscopic to large (meters). Photosynthetic – chloroplasts (Chl a only)
• chlorophyll is most likely derived from a cyanobacterium (Chl a) by endocytosis (endosymbiotic evolution)
hyphae (filaments without gametangia (where gametes crosswalls) are formed) (diameter ~ 10 µM)
GROUP 4. R ED ALGAE (RHODOPHYTA ) GROUP 5. CHLOROPHYTA –CHLOROPHYLL A,B Red algae (marine tidal zones) have Chl a, but are red because of a blue light absorbing Green algae – predecessors of land plants pigment, phycoerithrin (also in cyanobacteria). fossil record dates back 900 million years (0.9 Ga) aquatic (marine, estuarine and freshwater) Chlamydomonas – ancestral genus
4 GROUP 6. EUGLENOIDS GROUP 6. EUGLENOID PARASITES Euglenoids – mainly freshwater Flagellated unicells, endobionts in specific biting insects about one-third are photosynthetic (PS) Trypanosomes -- cause serious human diseases pellicle – strips of contractile protein • African sleeping sickness – mammal hosts (in blood vessels, invade nerve system) – 80% lethal to humans stigma (eye spot) – light sensitive organ aids in phototaxis • Chagas (tropical USA and South America) -- >1000 genes for glycoprotein coat; only 1 expressed at a time , thus food groove – enhances phagocytosis dodges antibodies easily (cf. bacterial pili). Tropical organotrophy, phagotrophy infections lead to heart and digestive problems. mixotrophy – more than one type of Epidemic proportions in humans. nutrition (mixed): PS ± phagocytosis ± organotrophy include non-PS trypanosomes (next slide)
Trypanosoma Vector: Tsetse fly
GROUP 7. CHOANOFLAGELLATES POORLY CLASSIFIED GROUPS (F LAGELLATES WITH A COLLAR ) AMOEBAE –DIFFICULT TO CLASSIFY Choanoflagellates are most like the common ancestor of the sponges (simple animals) Animals Contain pseudopods that can form at any point on the contain one emergent flagellum surrounded by a cell body and move in any direction funnel-shaped, contractile “collar” of tiny ‘tentacles’ One group (radiolarians -- marine) secretes glassy exoskeletons of silica (cf. diatoms).
More amoebae: Sand Stars POORLY CLASSIFIED GROUPS A star-shaped foram found on Japanese beaches AMOEBAE –DIFFICULT TO CLASSIFY
Foraminifera (“Forams”) – heterotrophic, marine, with pore-studded silica shells (different from diatoms) complex life cycle with alternation between haploid and diploid generations heterotrophic, marine organisms
5 A variety of centric diatoms
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