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Protists A Microbial Grab Bag
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On completing this chapter, you should be able to:
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Protist Characteristics
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Cilia
Flagella
Pseudopods
Protist characteristics
Reproduction
Mostly by mitosis
Some sexual reproduction occurs in some species.
Other characteristics
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Over 100,000 species identified
A mixture of characteristics across the spectrum
Believed that this was the point where plants, animals and fungi my have
branched off
Protist comes from the Greek meaning the “very first”
All protists are unicellular but some exist in colonies
Generally microscopic but some as big as a mm
Food gathering
Some phagocytize
Some absorb
Some photosynthesize
Movement
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Explain some general features of protists, including their structures and
physiological processes;
Appreciate the characteristics of four groups of protozoa, and explain how these
microbes influence society;
Name and briefly describe several protozoal diseases that affect humans;
Describe the complex patterns of reproduction displayed by various protists and
compare them to patterns observed in other microbes;
List the key features of several groups of single-celled (unicellular) algae;
Conceptualize the important roles played by unicellular algae in the oceans of the
world;
Make some generalizations about the two major types of slime molds and
understand why they are important as research tools.
Some resemble plants
Some resemble animals
Some resemble fungi
Zooplankton
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Animal-like components of aquatic food chain
Convert the algal cellular components into nutrients
Nutrients absorbed and digested by other consumers
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Protist contributions
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Many are decomposers
Recycle nutrients
Part of the aquatic food chain
 Zooplankton (a protozoa)
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Animal-like components of aquatic food chain
Feed on Algae and convert these into usable nutrients
Nutrients absorbed and digested by other consumers
The Protists
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Protozoa
Unicellular algae
Slime molds
o Eukaryotes
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Unicellular and multicellular forms
Asexual reproduction typical, but some sexual
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The Protozoa
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Characteristics
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Trophozoites
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Active feeding forms of protozoa
Transform into cysts in difficult environments
Four groups of protozoa
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Once believed to be “first animals”
No cell walls
Ingest food particles
Move freely
No spores
Ameobae
Flagellates
Ciliates
Sporozoa
Amoebae
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Pseudopodia
Sarcodines (another term for amoebae meaning fleshlike)
Not photosynthetic
Tests
Hardened shells
 Foraminifera
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elaborate chalky shells of calcium carbonate
Remains build up as dense deposits (e.g., Cliffs of Dover)
Heliozoa
 Freshwater amoebae
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Shells of silicon dioxide
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Radiolaria
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Sea-borne
Silicone dioxide shells that look like Christmas tree ornaments
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Amoeba movement
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Amoebae
o Human pathogens
 Entamoeba histolytica
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Amoebiasis
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Acanthamoeba
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Corneal infections in contact lens wearers
Home humidifiers
Allergic reaction
Humidifier fever
Flagellates
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Contaminated food and water
Intestinal ulcers
Sharp, appendicitis-like pain
Flagella used for locomotion
Endosymbiotic theory of eukaryotic evolution
Engulfing of one primordial aerobic prokaryote by primordial eukaryote
 Development of mitochondria
 Each provided benefit for the other
 Flagella perhaps also explained by endosymbiosis
 Attachment of spirochete to outside of eukaryotic cell
 Descendants evolved into flagella
Flagellates
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Trichonympha
Cellulose-digesting microbes in termites’ guts
Extensive populations in human intestines
Span the gap between unicellular and multicellular organisms
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Volvox
Gonium
Pandorina
o Human pathogens
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Trypanosoma brucei: African sleeping sickness
Trypanosoma cruzi: South American sleeping sickness
Giardia lamblia: nausea, gastric cramps, watery diarrhea
Trichomonas vaginalis: sexually transmitted disease
Leishmania tropica: leishmaniasis
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The Protozoa: Leishmaniasis
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Ciliates
o Hair-like cilia
o 10 M (0.01 mm) to 3 mm
o Synchronized motion of cilia controlled by primitive nerve network
o Macronucleus
o Micronuclei
o Paramecium
 Pellicle
 Trichocysts
 Contractile vacuoles
 Conjugation
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The Protozoa: Paramecium Conjugation
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Ciliates
o Non-motile ciliates
 Vorticella
 Stentor
 Cirri
Sporozora
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Also known as apicomplexans
Produce sporelike bodies
Almost all sporozora are parasitic
 Plasmodium: genus of sporozoa that causes malaria
 Toxoplasma gondii: cause of toxoplasmosis
 Pneumocystis carinii: pneumonia, especially AIDS patients
 Cryptosporidium coccidi: vomiting, diarrhea, etc.
 Cyclospora cayetanensis: intestinal illness
Movement of Cilia
The Protozoa: Toxoplasmosis
Anatomy of a Killer
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1993 Milwaukee, Wisconsin
Cryptosporidium coccidi outbreak in municipal water supply that was drawn from
Lake Michigan
Commonly exist in animal digestive tracts
Cause abdominal cramps, vomiting, fever, voluminous diarrhea
Temporarily solved by trucking in water, shutting off water fountains
Dinoflagellates
o Red tide
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Generate toxin
 Toxin concentrates in molluscs (e.g., mussels, clams, and scallops
 Humans eat contaminated molluscs and experience transient
neuromuscular deficiencies
Blooms of red tide can also be directly ingested by swimmers
Blooms deplete oxygen in water, leading to death of plants and animals,
generating putrid stench of decay
Unicellular Algae
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Simple, single-celled, photosynthetic microbes
Also known as phytoplankton (wandering plantlife)
Responsible for most of the molecular oxygen currently in our atmosphere.
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About half the worlds organic matter is produced by phytoplankton
Are divided into six distinct groups. We will discuss four.
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Pyrrophyta
Chrysophyta
Euglenophyta
Chlorophyta
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Pyrrophyta
o Fire-algae
o Red and orange pigments
o All are Dinoflagellates
o Have the capacity to move via flagella
o Photosynthesize
o Rigid walls of cellulose encased in silicon
o Some species are bioluminescent
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Chrysophyta
o Yellow-green algae
o Includes diatoms
o Intricate silicon dioxide shells
o Shells can be identified that are over 65 million years old.
o Diatomaceous earth
o Pseudonitzschia: potentially pathogenic
o Source of vitamins A & D for some animals
Euglenophyta
o Most in genus Euglena
o Two flagella
o Grow autotrophically in light
o Grow heterotrophically in dark
o Eyespot to detect light
Chlorophyta
o Unicellular and multicellular lifestyles
o Carotenoids and chlorophylls
o Synthesize and store starch
o Chlamydomonas
 Alternation of generations
o Snow algae
o Volvox
 Also considered a protozoan
 Community of independent cells
Other Protists: Alternation of Generations in Chlamydomonas
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Slime molds
o Microbes that exhibit animal-like and plant-like characteristics
o Have cellulose in the cell walls like plants
o At some point in their life cycle they move like animals.
o Two major groups
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Acellular slime molds (Myxomycota)
Cellular slime molds (Acrasiamycota)
 Acrasia: confusing
 Can form a slug when food is in short supply
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Slime molds
 Myxomycota
o Acellular slime molds
o Also known as plasmodial slime molds (plasmodium)
o One huge, multinucleated cell that resembles an amoeba
o A single, mutinucleate cell can become large enough to cover a log about
1mm thick.
o Saprophytic
o Fruiting bodies
 Acrasiomycota
o Cellular slime molds
o Cells retain individuality when congregated
o Slug
o Spore-producing stalk
o Sporangia
o Example: Dictyostelium discoideum
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Water molds
o Grow in damp soils
o Cause the furry growth in your fish tank
o Look like fungi
o Not fungi
o More cellulose than chitin
o Histones
o Phases of sexual reproduction
o Zoospores
 Flagellated spores
 Two flagella
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Phytophthora infestans: potato blight (Irish Potato Famine)
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In Summary
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Be sure you understand the information specified in the objectives at the beginning of this
presentation.
Know what a protist is.
Be able to describe the classes of protists
Be able to describe the different forms of motility associated with protists.
Understand their feeding form vs cysts.
Know any pathogenic effects caused by specific protozoa mentioned in this presentation
Know your vocabulary at the end of the chapter.