Kingdom Protista
KEY CONCEPTS
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Protists are a diverse group of
eukaryotic organisms, most of which are
microscopic
Protista
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Not a really valid “Kingdom”
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Few real evolutionary relationships
Contains
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Algae: “plant-like” protists
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Protozoa: “animal-like” protists
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Slime & Water molds: fungal-like
protists
What Are Protists?
“Dumping ground”
kingdom
• Eukaryotic
• Heterotrophic and/or
autotrophic
• Single or
multicellular
• Ancestors to
animals, plants,
fungi
•
Animal-like Protists
• Called Protozoans
• Unicellular
• Require water (live in
water or moist soil)
• Most heterotrophic
• Some photosynthetic
• Most are free-living
• Some parasitic
All Life Functions in Just One Cell
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Have food and waste
VACUOLES for storing
and digesting food &
wastes
Many are capable of
MOVEMENT
RESPOND to
environment – some
have light sensitive
eyespot
Amoeba
Paramecium
All Life Functions in Just One Cell
•
Maintain
HOMEOSTASIS
Contractile Vacuoles
pump out excess
water
• Form Protective Cysts
when food or water is
scarce (dormant stage
with hard covering)
•
Contractile Vacuole
Pumping
Plant-like Protists
• Photosynthetic
• No true roots, stems,
leaves
Golden Algae
Red Algae
Plant-like Protists
• Photosynthetic
• No true roots, stems, leaves
Green Algae
Brown Algae
Golden Algae
Red Algae
Fungi-like Protists
• Heterotrophic
• Decomposers
• No cell walls
Slime Molds
Water Molds
Reproduction
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Reproduction
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Asexual: fission
Sexual: produce gametes (specialized sex
cells)
• Advantage: new combinations of genes from
both parents (Red Queen Hypothesis)
Reproduction
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All reproduce
ASEXUALLY
Binary Fission divides into 2
identical
individuals
(clones)
Rapid
reproductive rate
Some Reproduce SEXUALLY
Conjugation - Opposite mating strains pair
and exchange genetic material (DNA)
Protist
Characteristics
General Characteristics
Eukaryotic
• Unicellular
• Some may live in colonies
• May be Autotrophic or
Heterotrophic or Both
• Some are motile
• Appeared about 1.5 BYA
•
Classified into Three Main Groups
Animal-like… heterotrophs
capable of locomotion
• Plant-like… photosynthetic
autotrophs
• Fungus-like… decomposers that
reproduce by spores
• Some protists may exhibit both
animal-like & plant-like
characteristics
•
Sizes of Protists
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Unicellular organisms
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Colonies
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loosely connected groups of cells
Coenocytes
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microscopic
multinucleate masses of cytoplasm
Multicellular organisms
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composed of many cells
can get very large – some brown algae (the
giant kelps) can be 100 feet in length
Locomotion
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Protozoa used to be classified according
to how they move.
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Ciliates use fine “hairs” called cilia
Flagellates use longer, whip-like hairs called
flagella
Amoebas and their relatives use pseudopodia
• Pseudopodia are also used to capture food
Sporozoans (apicomplexans) don’t have any
ability to move (non-motile)
Importance
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Importance of Protists
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Heterotrophic protists = protozoa
• Consume bacteria and other protists
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Components of aquatic and soil food webs
help with recycling nutrients
• Some cause disease
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Malaria
Dysentery
Sleeping sickness
others
Interactions
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Protists are free-living or symbiotic
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Symbiotic relationships range from
mutualism to parasitism
Classification of Selected Medically
Important Protozoa
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Four groups
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Mastigophora - flagellates
Sarcodina - amoebae
Ciliophora - ciliates
Apicomplexa – aka Sporozoans
Based on:
• Method of motility
• Mode of reproduction
• Stages in the lifecycle
Animal-like
Protists
classified by
method of
movement
Phylum Rhizopoda
(formerly Sarcodina) : ex. Amoeba
The Amoeba uses
pseudopodia for locomotion.
The Amoeba in 3D – notice
the pseudopods
Amoeba surround and engulf their
food… the process is called
phagocytosis.
An Amoeba eating a
Paramecium.
Ciliophora
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all use cilia for movement
have many specialized structures,
including mouths, anal pores,
contractile vacuoles, and two nuclei
(a large macronucleus and small
micronuclei)
Ex. – Paramecium and Stentor
Phylum Ciliophora: ex. Paramecium
3D view – taken by a
scanning
electron microscope
A closer look at the Cilia….
its means of locomotion
another Ciliate: Stentor
Phylum
Zoomastigophora
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have flagella
some species of
zooflagellates
have mutualistic
relationships
ex.- Trichonympha
digests cellulose
in the guts of
termites
Others are parasites, like
Trypanosoma, which causes
African Sleeping Sickness (coma).
Trypanosoma
Trypanosoma
Red Blood Cells
Trypanosoma
White Blood Cell
Tsetse Fly: carries Trypanosoma to
humans; in other words, it’s a Vector
Phylum Sporozoa
are parasites
• have no means of locomotion
• form spores that are dispersed
by one or more hosts
• ex. Plasmodium, which causes
malaria
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Portions of the Life Cycle of
Plasmodium vivax
Plasmodium vivax
It’s
Vector:
Anopheles
Mosquito
Red Blood Cells
Pathogenic Flagellates:
Trypanosomes
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Giardia lamblia
Trichomonas vaginalis
Genus Trypanosoma
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T. brucei causes sleeping sickness
T. cruzi causes Chagas disease
Giardia
Giardiasis
Fecal-oral route of infection
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recreational water, water, fomites, contaminated
uncooked food
• Symptoms normally begin 1 to 2 weeks (average 7
days) after becoming infected.
• Symptoms
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Diarrhea
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Gas or flatulence
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Greasy stools that tend to float
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Stomach or abdominal cramps
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Upset stomach or nausea
• May lead to weight loss and dehydration
• Symptoms of giardiasis may last 2 to 6 weeks.
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Trichomonas vaginalis
A flagellate - causes
Trichomoniasis, a sexually
transmitted disease
Trichomoniasis
STD
• Clinical Features:
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Trichomonas vaginalis infection in women is
frequently symptomatic.
Vaginitis with a purulent discharge is the
prominent symptom, and can be accompanied by
vulvar and cervical lesions, abdominal pain, dysuria
and dyspareunia.
The incubation period is 5 to 28 days.
In men, the infection is frequently asymptomatic;
occasionally, urethritis, epididymitis, and
prostatitis can occur.
Tsetse fly
Tsetse Fly
Trypanosomes
(flagellates) in blood
smear
Kissing bug
Red blood
cells
Trypanosome
with undulating
membrane
Flagellum
25 µm
T. cruzi causes
Chagas disease
Figure 5.27
African Sleeping Sickness
East Africa
West Africa
African Sleeping Sickness
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Bite reaction
Parasitemia
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CNS Stage
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attacks of fever which starts 2-3 weeks
after the bite
changes in character and personality
Terminal stage is marked by wasting and
emaciation
Death results from coma, intercurrent
infection or cardiac failure
Sarcodina (Amoebas)
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Pseudopods
Some have flagellated reproductive states
Asexual reproduction by fission
Two groups have an external shell
Mostly uninucleate
Usually encyst
Most free-living
Examples
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Entamoeba
Foraminifera
Radiolarians
Figure 5.24
Infective Amoebas: Entamoeba
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Amoebiasis caused by Entamoeba
histolytica
Fourth most common protozoan
infection in the world
Aka amoebic dysentery
Entamoeba histolytica
Figure 5.28
Entameoba histolytica
Causes amoebic
dysentery (diarrhea)
and can enter the liver,
lungs, and brain
Naegleria fowleri
Foraminifera
More support for the theory:
Living organisms that contain
endosymbiotic bacteria that carry
out vital functions in the cell.
Cyanophora paradoxa - has no
chloroplasts; contains an
endosymbiotic cyanobacterium.
Pelomyxa has no
mitochondria; this
amoeba depends on
aerobic bacterial
symbionts to carry out
respiration
Amoebae
Ciliophora (Ciliated)
Trophozoites mobile by cilia
• Some have cilia in tufts for feeding and
attachment
• Most develop cysts
• Both macronuclei and micronuclei
• Division by transverse fission
• Most have definite mouth and feeding
organelle
• Show relatively advanced behavior
• Majority are free-living and harmless
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Ciliates
Balantidium coli
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Only known ciliate that is pathogenic in
humans
Affects humans, other primates, and pigs
which are the reservoir
Lives in the large intestine and causes
diarrhea
Trophozoites can also be detected in tissue.
Collect a tissue specimen from the large
intestine, by sigmoidoscopy
Trophozoites
Cyst
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Most cases are asymptomatic.
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Clinical manifestations, when
present, include persistent
diarrhea, occasionally dysentery,
abdominal pain, and weight loss.
Symptoms can be severe in
debilitated persons.
Diagnosis is based on detection
of trophozoites in stool
specimens or in tissue collected
during endoscopy.
• Repeated stool samples
• Treatment
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Tetracycline with metronidazole
and iodoquinol as alternatives
Apicomplexa (Sporozoa)
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Most not motile except male gametes
Complex life cycles
Produce sporozoites following sexual
reproduction
Important in transmission of infections
Most form oocysts
Entire group is parasitic
Examples
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Plasmodium spp.
Toxoplasma gondii
Cryptosporidium parvum
Mosquito - transmits the
malaria parasite Plasmodium
vivax (a sporozoan)
Malaria parasite in
red blood cells
Parasites breaking
out of red blood
cells
Malaria
Toxoplasmosis
Toxoplasmosis
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Parasite causes eye and brain damage in a
baby, if untreated.
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Acute infection in older children and adults
may be without symptoms, cause flu like
illness or enlarged lymph glands.
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Latent parasite occurs very commonly in
people infecting approximately a third to a
half of all humans.
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Can cause active disease if a person becomes
immune compromised
Protozoan Identification and
Cultivation
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Shape and size of cell
Type, number, and distribution of
locomotor structures
Presence of special organelles or cysts
Number of nuclei
Can be cultivated on artificial media or
in laboratory animals
Toxoplasma gondii
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Clinical Features:
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Generally an asymptomatic or mild self-limiting
infection.
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Immunodeficient patients
• brain lesions
• pneumonitis
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Pregnant women/infant
• miscarriage; still births
• cerebral palsey; seisures
• mental retardation
• eye infections; impaired
vision
• enlarged liver and spleen
Cryptosporidium affects
humans, dogs, and cattle
Cryptosporidium can be a problem in
municipal water supplies.
Cryptosporidium
Intracellular parasite
Causes diarrhea
Affects humans, cattle,
sheep, dogs
No effective drug
treatment for
cryptosporidiosis
Antibiotics are
contraindicated;
supportive care only
Important Protozoan Pathogens
Phylum Foraminifera
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have a protective shell or TEST, usually
made of calcium carbonate
layers of tests can deposit on the ocean
floor
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these can form limestone and chalk, like
the White Cliffs of Dover
Some species of forams are good indicators
of oil deposits below
Cliffs of
Dover
Plant-like Protists
are classified by
COLOR
Plant Like Protista
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Importance of Protists
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Autotrophic protists = algae
• Photosynthetic algae are the most important
primary producers of the world’s freshwater
and marine ecosystems
• Many are microscopic
• Some are huge: kelp
• Few cause disease
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Toxic blooms of dinoflagellates cause
• Red tides
• shellfish poisoning
Diatoms
Giant Kelp
Photosynthetic Producers
Photosynthesis
6 CO2 + 6H2O
6 C6H12O6
Respiration
Lake Trophic Levels
Bluegill
2o
consumers
Zooplankton
1o
consumers
Bass
3o
consumers
Algae - producers
Osprey
Humans
4o
consumers
Phylum Chlorophyta
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have both chlorophyll a and b (so they
are green)
have cellulose cell walls
store carbohydrates as starch
have many types of sexual reproduction
exhibit many types of organization
--Are thought to be the ancestors of
plants--
Variations in Sexual
Reproduction
Isogamous= both sperm and egg
are motile and equal in size
• Anisogamous= both sperm and
egg are motile and differ in size
• Oogamous= large, nonmotile egg
and small, motile sperm
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Variations in Sexual
Reproduction
Phylum Chlorophyta
organization
1.
2.
3.
4.
Unicellular
Filamentous
Colonial
Bi-layer
Unicellular Green Algae
Chlamydomonas
Chlamydomonas
Filamentous Green Algae
Spirogyra
has spiral-shaped chloroplasts
another filamentous Green Algae
Zygnema
2 Star-shaped chloroplasts per
cells
a colonial Green Algae … Volvox
Mother colony with Daughter
colonies
Mother Colony
Daughter Colony
a bi-layered Green
Algae
Ulva (sea lettuce)
Harvesting Ulva
Phylum
Phaeophyta
brown algae
• multicellular
• flagellated sperm
cells
• Ex.: Fucus & Kelp
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Phylum Pheaophyta:
Brown Algae… Laminaria… Kelp
Air Bladders:
Used to take blades
to the surface for
photosynthesis
Phylum Rhodophyta:
Red Algae
• are
multicellular
• contain red
accessory
pigments called
phycobilins
• gametes do not
have flagella
Phylum Dinoflagellata
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formerly known as Pyrrophyta or fire
algae
have two flagella
some are bioluminescent, producing
light
others produce nerve toxins
• dinoflagellates are collected and
concentrated in filter-feeding
animals
Phylum Dinoflagellata
ex. Peridinium
Red Tide-
results from a bloom
of Peridinium
Phylum Bacillariophyta:
Diatoms… have tests (shells) that
contain silica (SiO2), or glass
Diatom Strew
Diatoms - a SEM
picture
Phylum Euglenophyta
have one to three flagella at their
leading (apical) end
• have thin protein strips called
pellicles wrapped over their
membranes
• have an eyespot that permits them
to swim toward light
• can become heterotrophic when
there is no light
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Euglena
(arrow indicates anterior
end)
The Euglena uses a flagella as
a
means of locomotion.
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Phylum
Chrysophyta
Are golden yellow
Have one or two apical
flagella
MORE
Examples of Autotrophic
Protists (Algae)
Giant Kelp Forest
Desmids – a type of
green algae
Green and golden
algae
Summer
Tabellaria - a diatom Note the sheets
of rectangular cells
Asterionella - a diatom
Dinobryon
A chrysophyte algae – Early Spring
Gonyaulax (another
flagellate) and view of
red tide
Fungal Like
Protists
Habitats
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Most protists live in
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ocean
freshwater ponds
lakes
Streams
Soil
Parasitic protists live in body fluids of
hosts
Phylum Acrasiomycota:
Cellular Slime Molds
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have both fungus and protist characteristics
spores germinate into amoebas that feed on
bacteria
When food is depleted, cyclic AMP is released,
causing amoebas to aggregate into one unit
the crowd of amoebas form a slug that migrates
cells from the slug form a stalk with a capsule,
which makes spores
spores are released, and the cycle repeats
Acrasiomycota Life Cycle
Phylum Acrasiomycota
colony &
fruiting body
aggregating
amoebas
Phylum Myxomycota: Plasmodial
Slime Molds
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grow as a single, spreading mass or plasmodium
feed on decaying vegetation
when the environment becomes unfavorable (no
food or water), they form stalks and sporeproducing capsules
haploid spores germinate into amoeboid or
flagellated cells
these cells fuse to form a new diploid plasmodium
Myxomycota Life Cycle
Myxomycota
Phylum Oomycota
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are parasitic and saprophytic
form filaments, or hyphae (like fungi)
secrete enzymes into surroundings &
absorb nutrients (like fungi)
filaments lack septa or cross walls
resulting in many nuclei in a cell, they are
coenocytic
have cell walls made of cellulose, not
chitin
Oomycota
Life Cycle
Examples:
• water molds
• downy mildews
• white rusts
Leptomitus
Powdery Mildew
Phylum Oomycota
potatoes are native to North America
• they were introduced to Europe and
became a staple of the diet
• during the summer of 1846 most of
the potato crop was destroyed by
Phytophthora (an oomycota)
• nearly 1,000,000 Irish people died, and
1,500,000 emigrated to other
countries, like the U.S.
•
Ulcers on fish caused by
Pfiesteria
Pfiesteria piscicida.
Note the long flagella
Evolutionary Considerations
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One group of flagellates, the
choanoflagellates, is thought to
have given rise to the simplest
animals, the sponges.