Protists•First discovered by Leeuewenhoek after discovery of microscope- called “animalcules”

•All eukaryotes, mostly single celled, some multi-cellular but no specialized tissues

Kingdom Protista vs. “protists”•Classification of Protista and protists in flux

•Traditionally, Kingdom Protista is all eukaryotes that are not plant, animal or fungi (the misfits)

•Most diverse kingdom; many members resemble other kingdoms more than they do each other

•Group does not adhere to cladistics

•The term “protists” may refer to organisms no longer considered in the Kingdom Protista

5 Eukaryotic Supergroups: a phylogenetic hypothesis

•Attempt to arrange protists into true clades

•Based on molecular and/or structural evidence

•Plants, Animals, Fungi included

•Protists in yellow

•Dotted lines indicate uncertain relationships

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Why do we care about protists?•Autotrophic protists produce over 75% of our atmospheric oxygen

•Decomposer protists play an important role in eating dead organic matter and recycling materials in our ecosystem

•Certain kinds cause “red tide” and lead to build up of toxins in shellfish (can poison man; kill aquatic life)

•When certain inorganic nutrients are high, can cause bloom of protists; they multiply and cover top of water so no light penetrates and aquatic plants and animals die leading to eutrophication

Based on your microscopy observations a couple of weeks ago, how would you classify

protists?

nutritionautotrophs

heterotrophsmixotrophs

movementflagella

ciliapseudopodsnon-motile

other kingdom most likeanimal-likeplant-like

fungus-like

Here is how we will go through protists:

•Animal-like •Flagellates •Pseudopods •Ciliates •Sporozoa•Plant-like•Euglenoids•Dinoflagellates•Diatoms•Fungus-like•slime molds

Animal-like protists

•also called protozoans•heterotrophs

Animal-like protists: Flagellates

•many parasitize man•have long whiplike flagella used to move

•reproduce both sexually and asexually

Animal-like protists: Flagellates

Trypanosomes*

African sleeping sickness; South American Chagas disease

Animal-like protists: Flagellates

Trypanosomes* Nutrition: obligate parasite

Locomotion: single flagella and an undulating membrane

Protective adaptations: Change their surface antigens to avoid the host’s immune system. The change occurs usually at 3-week intervals, just when antibody is produced to the old antigen.

Other unusual characteristics: Sleeping sickness spread tse-tse fly. Chagas disease is can lead to congestive heart failure. These are zoonotic infections (transferred from animal to animal using a vector). Have a single large mitochondria with a mass of DNA called a kinetoplast.

Kingdom or Phylum: Kingdom Protista, Phylum Euglenozoa, Class Kinetoplastea

Animal-like protists: Flagellates

Trychonympha

Live in the guts of termites; make enzymes that digest cellulose for the termite; symbiotic relationship

Animal-like protists: Flagellates

Trichomonas vaginalis*

Causes sexually transmitted disease

Animal-like protists: Flagellates

Trichomonas vaginalis*

Nutrition: parasite; causes STD

Locomotion: multiple flagellae

Protective adaptations: Anaerobic.

Other unusual characteristics: No DNA and no electron transport chain in the mitochondria. 2 equal-sized nuclei.

Kingdom or Phylum: Kingdom Protista, Phylum or Clad Diplomonadida; some put in Kingdom Archezoa since lacks true mitochondria

Animal-like protists: Flagellates

Giardia

Anaerobic; intestinal parasite; spread through fecal-oral route by drinking contaminated food or water; big concern for campers using water sources near beaver dams

Animal-like protists: Pseudopods

•amoeba-like movement•eat by phagocytosis (contain actin + myosin)

•some responsible for human disease

•foraminifera and radiolarians are “shelled” amoeba

•radiolarians comprise “chert”- sedimentary rock made of silica

Animal-like protists: Pseudopods

Pelomyxa* Nutrition: heterotroph, takes in food by phagocytosis, eat protozoa and invertebrates

Locomotion: pseudopodia

Protective adaptations: Habitat is in freshwater mud. Tolerate very low levels of oxygen almost to point of being anaerobic.

Other unusual characteristics: Contain methanogenic bacteria that live in symbiotic relationship. Provide energy in place of mitochondria. Multinucleate and nuclei all divide together.

Kingdom or Phylum: Kingdom Protista or Kingdom Archezoa (due to no mitochondria); Phylum Amoebozoa

Animal-like protists: Pseudopods

Amoeba proteus*

Nutrition: heterotroph

Locomotion: pseudopods

Protective adaptations:

Other unusual characteristics: Can sense light and tends to move away from it. Just before it reproduces, it rounds up into a ball with tiny pseudopodia extensions. Over the next 15 minuts or so, it splits and becomes 2.

Kingdom or Phylum: Kingdom Protista, Clad Amoebozoa

Animal-like protists: PseudopodsEntameoba histolytica*

Nutrition: obligate parasite

Locomotion: pseudopod

Protective adaptations: can form cysts for survival during harsh conditions

Other unusual characteristics: passed by oral-fecal route; adheres to host lumen, can bore into intestinal wall, can cause amoebic dysentery and amoebic liver, lung or brain abscess; anaerobic; lack mitochondria

Kingdom or Phylum: Kingdom Archezoa

Animal-like protists: Pseudopods

Actinosphaerium*

Animal-like protists: Pseudopods

Actinosphaerium* Nutrition: heterotrophs feeding on small flagellates and ciliates and microscopic algae

Locomotion: pseudopodia supported by axopods radiating outward from the cell body, which adhere to passing prey and allow it to roll or float about

Protective adaptations: form a cyst, which is multi-walled and covered in spikes

Other unusual characteristics: fresh water; frequent in lakes and rivers; few found in marine and soil habitats; unicellular and roughly spherical in shape; called “heliozoan” or “sun animal”

Kingdom or Phylum: Kingdom Chromista; Protist kingdom: Phylum Cercozoae

Animal-like protists: Pseudopods

Foraminifera “shelled amoeba”

shell called a “test”

some secrete calcium carbonate shells

the foraminifera shells make up the limestone used to build the pyramids in Egypt

Animal-like protists: Pseudopods

Radiolarians

“shelled amoeba”

comprise “chert”- sedimentary rock made of silica

shell called a “test”; shell has pores that pseudopodia stick out of.

Animal-like protists: Ciliates•complex sub-cellular organization, form

vacuoles•contain oral groove and pellicle (protein layer beneath plasma membrane)

•2 nuclei types: Micro (diploid; divides by meiosis, involved in reproduction, forms macro) and macro (polyploid; nucleus which carries out cell’s functions)

•reproduction is asexual (the macro nucleus divides by splitting in half) and sexual (haploid micronuclei from meiosis exchanged by conjugation)

•contain trichocysts (used as tentacles to capture prey and as an anchor to attach to a surface)

Animal-like protists: Ciliates

Paramecium*

Animal-like protists: Ciliates

Paramecium* Nutrition: heterotroph; cilia line oral groove, food moves into pharynx, egest through the anal pore, eat protists and yeast

Locomotion: thousands of cilia, cellular extensions that extend through the pellicle

Protective adaptations: trichocysts reach surface through pores in the pellicle, can be discharged into fine threads; contractile vacuoles for water balance

Other unusual characteristics: live in fresh water, covered by a stiff, flexible pellicle, rounded front and pointed end, can regenerate if small piece of the nucleus is contained in the cut piece, two types of nuclei- macro and micro; reproduce by binary fission (asexual) and conjugation (sexual)

Kingdom or Phylum: Kingdom Protista, Clad Alveolata (membrane bound sacs under plasma membrane that look like alveoli in the lungs)

Animal-like protists: Ciliates

Stentor* Nutrition: heterotroph

Locomotion: cilia and circlet of membranes; heterotrichs because they have different cilial structures on different parts of body

Protective adaptations: lengthwise contractile fibers (myonemes similar to the Vorticella) that shorten the body

Other unusual characteristics: attaches when feeding; large nucleus resembling a string of beads and many small nuclei; amazing powers to regenerate even from a small portion of the cell; primary photosensor is called stentorin

Kingdom or Phylum: Same as Paramecium

Animal-like protists: Ciliates

Blepharisma*

Nutrition: heterotrophic filter feeders; eat bacteria found in decaying vegetation

Locomotion: move by cilia just like paramecium

Protective adaptations: photophobic; contain photosensory pigments in the pellicle located in pigment granules called blepharismins

Other unusual characteristics: pale pink to bright red with pigmentation granules; have undulating membrane and a single contractile vacuole with no canals

Kingdom or Phylum: same as Paramecium

Animal-like protists: CiliatesVorticella*

Nutrition: heterotroph; feeds mainly on bacteria

Locomotion: cilia around the broad end of the bell shaped body

Protective adaptations: can release the stalk and move to another location if needed; will regenerate the stalk; inside fibers of the stalk are myonemes that contract when disturbed

Other unusual characteristics: attach to substrate by the stalk; asexual reproduction by dividing lengthwise; also sexual by conjugation

Kingdom or Phylum: same as Paramecium

Animal-like protists: Sporozoa

•Apicomplexans (named for apical structure that helps parasite enter host cell)

•spore forming•internal parasites•alternation between haploid and diploid forms

•immobile

Animal-like protists: Sporozoa

Plasmodium* Nutrition: obligate parasite

Locomotion: no known method

Protective adaptations: apex contains complex of organelles used to penetrate the host cell

Other unusual characteristics: non-photosynthetic plastid or apicoplastid believed to originate from a chloroplast so these may have once been photosynthetic; transferred by the bite of the female Anopheles mosquitos; cause malaria

Kingdom or Phylum: Kingdom Protista; Phylum or clad Diplomonadida; some put in Kingdom Archezoa since it lacks mitochondria

Animal-like protists: Sporozoa

Plasmodium*

Plant-like protists: Euglenoidea

Euglena* Nutrition: photosynthetic or mixotrophs; can absorb nutrients through the cell membrane; storage molecule is paramylon

Locomotion: pocket at one end where 2 flagella come from; has euglenoid movement

Protective adaptations: one contractile vacuole for water balance; contains an eyespot or stigma that is light sensitive (positive phototropism)

Other unusual characteristics: flagellate protozoa; all protozoa are photosynthetic flagellates; has an elastic pellicle

Kingdom or Phylum: Kingdom Protista; Clad Euglenozoa; Euglenids

Plant-like protists: Dinoflagellates

Dinoflagellates*

Plant-like protists: DinoflagellatesDinoflagellates*

Nutrition: marine and freshwater phytoplankton so they are photosynthetic (contain chlorophylls); some heterotrophs

Locomotion: 2 flagella located in a groove; protective cellulose plates cover dinoflagellates

Protective adaptations: contain carotenoids; produce toxins eaten by mollusks and then humans; some cause Red Tide

Other unusual characteristics: cause red tide (contain carotenoids); main food source for the coral reefs; bioluminescence

Kingdom or Phylum: Kingdom Protista; Phylum Alveolata; Dinoflagellates

Plant-like protists: DiatomsDiatoms

•reproduce by binary fission•produce shells or “tests”•lack flagella•produce diatomaceous earth used commercially as filtering agents or abrasives

Fungus-like protists•slime molds•live on damp soil, logs, decaying matter•saprophytes- heterotrophs that obtain food by eating detritis

•life cycle- alternation of generation between plasmodium (vegetative) stage and fruiting body (spore-forming) stage

•plasmodium stage is multinucleate and forms long hyphae; this gives high surface area to volume ratio which makes for more efficient exchange/absorption of nutrients and materials across the cell membrane

Fungus-like protists: slime molds

REVIEW

Read CH. 28 on Protists in Campbell & Reece

zoonotic infection: infectious disease that can be transmitted from animals to humans and vice versa by a vector

vector: organism that does not cause disease but transmits disease by conveying pathogens from one host to another

Terminology

Trypanosomes, obligate parasites, are pathogens in...

African sleeping sickness•transmitted by bite of tse tse fly•affects multiple organ systems finally crossing blood-brain barrier to give classic “sleeping” symptoms

South American Chagas disease•transmitted by bite of blood-sucking assassin bug•early on symptoms mild; over years leads to intestinal malformations and heart failure

Malaria•caused by protozoan obligate parasite Plasmodium (an Apicocomplexans)•transmitted by bite of female Anopheles mosquito•infects blood and liver cells in human•part of life cycle in mosquito; part in human

250 million fevers, 1 million deaths annually

Malarial pathogen: The Life Cycle of Plasmodium

Sporozoite

Red Tide: Dinoflagellates

•nutrient imbalance can lead to bloom (overpopulation) of dinoflagellates leading to Red Tide•dinoflagellates produce neurotoxin that kills fish and accumulates in filter feeders like shell fish•affects food supply as fish die and shell fish become toxic to eat

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