Eukaryotic Cells
Characteristics; Fungi; Protozoa; Helminths
I.
Characteristics of Eukaryotes
A. Flagella
1. Long, sheathed cylinder; 9+2 microtubule arrangement
2. Covered by extension of cell membrane
3. 10x thicker than prokaryotic flagella
4. function in motility
B. Cilia
1. Similar to flagella but shorter, more numerous
2. Only on a single group of protozoa; certain animal cells
3. Motility, feeding, filtering
4. In rows; oar-like strokes
C. Glycocalyx
1. Outermost boundary in contact with environment
2. Usually polysaccharides
3. Network of fibers, slime layer, or capsule
4. Functions in adherence, protection, signal reception
5. Beneath may be cell wall or cell membrane
D. Cell Wall
1. Rigid; structure, support, shape
2. Fungi- chitin or cellulose and glycans
3. Algae- varies; cellulose, pectin, mannans, silicon dioxide
E. Cell membrane
1. Bilayer of phospholipids and proteins
2. Sterols for stability
3. Selectively permeable
4. Membrane organelles – 60-80% of their volume
F. Nucleus
1. Compact sphere; most prominent organelle
2. Nuclear envelope – two membranes and pores
3. Contains chromatin and histones
4. Nucleolus – rRNA synthesis; ribosome assembly
G. Endoplasmic Reticulum
1. RER – from outer membrane of nucleus to celll membrane;
has ribosomes; proteins are synthesized and shunted into
ER for packaging and transport
2. SER- closed tubular network without ribosomes; functions
in nutrient processing, synthesis and storage of lipids, etc.
H. Golgi apparatus
1. Stack of flattened sacs called cisternae
2. Associated with ER
3. Protein modification and maturation
4. Transport proteins in vesicles
II.
I. Lysosomes
1. Vesicles containing enzymes
2. Intracellular digestion and protection
3. Removal of cell debris
J. Vacuoles
1. Membrane-bound sacs
2. In phagocytic cells
3. Storage
4. Contractile
K. Mitochondria
1. Outer membrane and inner membrane; cristae
2. Cristae hold enzymes
3. Contain own DNA and ribosomes
4. Energy production; ATP
L. Chloroplast
1. In algae and plants
2. Have photosynthetic pigments
3. Convert sunlight energy into chemical energy
M. Cytoskeleton
1. Framework of proteins, microfilaments, microtubules that
form network
2. Movement of cytoplasm, ameboid movement, transport,
structural support
N. Ribosomes
1. rRNA and proteins
2. 40S and 60S subunits form 80S ribosome
3. Larger than prokaryotic ribosomes
4. Protein synthesis
Kingdom Fungi
A. Microscopic fungi
1. Two morphologies
a. Yeast
b. Hyphae
2. Dimorphic
B. Fungal nutrition
1. Heterotrophic
2. Most are harmless saprobes
3. Some are parasites, cause mycoses
C. Organization of Microscopic Fungi
1. Colonies
2. Mycelium
D.
E.
F.
G.
H.
I.
J.
K.
3. Vegetative hyphae
4. Reproductive hyphae
Fungal Reproduction
1. Spores
a. Asexual
b. Sexual
Four Main Divisions
1. Zygomycota
2. Ascomycota
3. Basidiomycota
4. Deuteromycota
Fungal Identification
1. Isolated on special media
2. Observed macro- and microscopically
3. Asexual spore-forming structures
Roles of Fungi
1. Decomposers
2. Antibiotics
3. Foods and genetic studies
4. Adverse impact
Mushrooms
1. Toxins and hallucinogens
2. Amanita muscaria
3. Amanita phalloides
4. Amanita caesarae
Fungi as Infectious Agents
1. Humans relatively resistant
2. Fungi relatively nonpathogenic
3. Most common plant pathogens
4. Human mycoses caused by true pathogens and by
opportunistic pathogens
Mycoses
1. True pathogen grows in healthy animal host
2. Opportunists in weakened host
3. Some grow when inoculated into skin
4. Most don’t require a host and aren’t communicable
5. Dermaphytes and Candida inhabit humans; transmissible
Systemic Infections by True Pathogens
1. Restricted to endemic regions
2. Spores are inhales
3. Spores germinate in lungs into yeasts; primary pulmonary
infection
4. Infection may become systemic
5. Result in immunity
L. Histoplasmosis
1. Histoplasma capsulatum
2. Dimorphic
3. Ohio Valley; moist soils
M. Coccidioides immitis
1. Coccidioidomycosis
2. Distictive morphology
3. Endemic to southwestern U.S.
4. Arthrospores inhales, creates spherules & nodules in lungs
5. Amphotericin B treatment
N. Blastomyces dermatitidis
1. Blastomycosis
2. Dimorphic
3. 10-100 inhales conidia convert to yeasts in lungs
4. Fever, cough
5. Chronic cutaneous, bone, nervous system complications
O. Subcutaneous mycoses
1. Lymphocutaneous sprotrichosis
2. Chromoblastomycosis
3. Mycetoma
P. Sporothrix schenckii
1. Rose-gardener’s disease
2. Infects appendages and lungs
3. Penetrates skin, forms nodule, spreads to lymph nodes
Q. Mycetoma
1. Soil microbes accidentally implanted into skin
2. Progressive, tumorlike disease of hand or foot
3. Pseudallescheria, Madurella
R. Cutaneous mycoses
1. Infection of keratinized epidermis- dermatophytoses;
ringworm
2. 39 species of Trichophyton, Microsporum,
Epidermophyton
3. Communicable
4. Ringworm of scalp- hair may be lost
5. Ringworm of body
6. Ringworm of groin
7. Ringworm of foot & hand
8. Ringworm of nails
S. Candida albicans
1. Normal flora
2. 80% of nosocomial fungal infections
3. 30% deaths of nosocomial infections
4. Thrush
III.
5. Vuvuvaginal yeast infection
6. Cutaneous candidiasis
T. Crytococcus neoformans
1. Widespread around pigeon roosts
2. Causes crytococcosis
3. Common infection of AIDS, cancer, diabetes
4. Infection of lungs
5. Dissemination
U. Pneumocystis carinii
1. Causes pneumonia
2. Most prominent opportunistic infection in AIDS
3. Secretions in lungs
V. Aspergillus
1. Common soil fungus
2. Fungus balls in lungs; disease in eyes, heart, brain
Kingdom Protista
A. Protozoa
1. Unicellular
2. Locomotor structures
3. Vary in shape
4. Lack cell walls and chloroplasts
5. Exist as trophozoite or cyst
6. Heterotrophic
7. Most are free-living in moist habitat
8. Some are parasites; spread by vectors
B. Groups based on locomotion and reproduction
1. Mastigophora-flagellates
2. Sarcodina-amoebas
3. Ciliophora-ciliates
4. Apicomplexa-all parasites
C. Mastigophora
1. Hemoflagellates
a. Live in blood and tissues of human host
b. Obligate parasites
c. Zoonoses
d. Insect vectors
e. In tropical regions
f. Complicated life cycles
2. Trypanosoma
a. Trypomastigote
b. T. brucei
c. T. cruzi
3. Trypanosoma cruzi
a. Chaga’s disease; Central and South America
b. Reduviid bug (kissing) vector
c. Bug feces inoculated into wound
d. Local lesion, fever, swelling of lymph nodes,
spleen, liver
e. Heart , large intestine harbor amastigotes
f. Chronic inflammation
4. Chaga’s disease
a. Acute stage-chagomas
b. Generalized stage-fever, swollen lymph nodes
c. Chronic stage-asymptomatic
d. Symptomatic stage – congestive heart failure
5. Trypanosoma brucei
a. African sleeping sickness
b. Vector-tsetse fly
c. Mammal reservoir
d. Bite of fly inoculates skin with trypanosomes;
multiply in blood, damage spleen, lymph nodes,
brain
e. Chronic symptoms-sleep disturbances, tremors,
paralysis, coma
f. Treatment must be before neurological involvement
g. Cyclical waves of parasitemia
6. Leishmaniasis
a. Zoonosis; mammalian hosts; vector is female sand
fly
b. Infected macrophages carry pathogen into skin and
bloodstream; fever, enlarged organs, anemia
c. Cutaneous-skin ulcers around bite wound
d. Mucocutaneous-lesions enlarge
e. Visceral- spread to liver, spleen, bone marrow
f. Most cases heal without treatment and confer
immunity
7. Giardia lamblia
a. Heart shape; looks like a face
b. Cysts small, multinucleate; survive 2 months
outside host
c. Cysts enter duodenum, germinate, travel to
jejunum, multiply
d. Giardiasis-diarrhea, abdominal pain
e. Agent killed by boiling, ozone, iodine
f. Prevention – filter water
g. Water-borne infection
h. “Beaver fever”
8. Tricomonas
a. Small, pear-shaped
b. Only in trophozoite form
9. Trichomonas vaginalis
a. STD – trichomoniasis
b. Reservoir is human urogenital tract
c. 50% asymptomatic
d. Can’t survive long outside host
e. Female symptoms-foul-smelling, green-to-yellow
discharge, vulvitis, cervicitis
f. Male – urethritis, thin, milky discharge
10. Trichomonas tenax
a. Only flagellate in oral cavity
b. Not a true pathogen; opportunist
D. Sarcodina-amoebas
1. Amoebae
a. No defined shape
b. Pseudopods
c. Few cause disease
2. Entamoeba histolytica
a. Alternates between trophozoite and cyst
b. Humans primary hosts
c. Ingested
d. !0% of world population carries it
e. Cysts swallowed, go to small intestine, release 4
trophozoites
f. Trophozoites multiply, feed
g. 90% asymptomatic
h. Cause dysentery, abdominal pain
i. May cause hemorrhage, perforation; may invade
liver & lung
3. Amoebic brain infections
a. Naegleria fowleri, Acanthamoeba
b. Inhabit standing water
c. Meningoencephalitis; usually fatal
E. Ciliates
1. Balantidium coli
a. Lives in intestines
b. Ingesting cyst-containing water or food
c. Trophozoite erodes intestine
d. Healthy humans resistant
e. Rarely penetrates intestine or enters blood
F. Apicomplexan parasites
1. Sporozoans
2.
3.
4.
5.
IV.
Lack locomotor organelles
Alternate between sexual and asexual phases
Most form specialized infective bodies
Plasmodium
a. Causes malaria
b. Vectoe-female Anopheles mosquito
c. Obligate intracellular sporozoan
d. Four species
e. 300-500 M new cases each year
f. 2 million deaths each year
g. Sporozoites enter blood, penetrate liver cells,
multiply, form hundreds of merozoites, which
multiply in and lyse RBCs
h. Symptoms-chills, fever, sweating, anemia, organ
enlargement
6. Toxoplasma gondii
a. Extensive distribution
b. Lives in cats; oocysts in GI tract
c. Acquired by ingesting raw meats or substances
contaminated by cat feces
d. Most cases unnoticed except if fetus and AIDS
7. Cryptosporidium
a. Intestinal pathogen
b. Contaminated water
c. Enteric symptoms
d. AIDS patients may suffer chronic diarrhea;
indicator disease for clinical stage of AIDS
e. No real effective drug; oral rehydration
Parasitic Helminths
A. Multicellular animals
B. Mouthparts for attachment to or digestion of host tissues
C. Well-developed sex organs
D. Larval period in or out of body
E. Major Groups of helminthes
1. Flatworms-no definite body cavity, digestive tract a blind
pouch
2. Roundworms- complete digestive tract; spines and hooks
on mouth
F. Helminths
1. 50 species parasitize humans
2. Ingestion of larvae or eggs in food; from soil or water;
some carried by insect vectors
3. Affect billions of humans
G.
H.
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J.
K.
L.
M.
4. Adults live in definitive host
5. Eggs and larvae in intermediate host
6. Pathology from worms feeding on and migrating through
tissues and accumulation of worms and worm products
7. drugs paralyze their muscles or interfere with metabolism
Cestodes
1. Tapeworms lack digestive systems
2. All posses same general body plan
Tapeworms
1. Flatworms
2. Long, thin ribbonlike bodies; proglottids and scolex
3. Proglottid absorbs food , makes, releases eggs
Taenia
1. Taenia saginata –beef tapeworm
2. Taenia solium – pork tapeworm
3. Cattle, swine intermediate hosts; infected by eating
contaminated vegetation
4. Humans ingest cysticerci in raw or undercooked meat
5. Adults attach to intestinal epithelium
6. Blockage of intestine can occur
Taenia saginata
1. Beef tapeworm
2. Up to 2,000 proglottids
3. Humans definitive host
Taenia solium
1. Pork tapeworm
2. Humans ingest cysts or eggs
3. Eggs hatch in intestine, releasing tapeworm larva that
migrate to all tissues and encyst
4. Most damaging if they lodge in heart , eye, brain
5. May cause seizures, psychiatric disturbances
Echinococcus granulosus
1. Tapeworm of canines
2. Canines infected by eating cysticerci in various herbivore
hosts
3. Humans are accidental intermediate hosts
4. Infections from consuming food or water contaminated
from dog feces
5. Causes hydatid disease
6. Larvae invade blood and travel throughout body
7. Form hydatid cysts; large number can be fatal
8. Avoid fecal-oral transmission from infected pets
Trematodes or Flukes
1. Flatworms with ovoid leaflike bodies
N.
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Q.
R.
S.
2. Snails or fish usually intermediate hosts and humans
definitive hosts
Blood flukes: Schistosomes
1. Schistomiasis is 2nd most prominent parasitic disease
2. Adult flukes live in humans and release eggs into water.
Early larva develop in freshwater snail into a 2nd larva
3. This larva penetrates human skin and moves into liver to
mature; adults migrate to intestine or bladder and shed
eggs, giving rise to chronic organ enlargement
Representative Liver Flukes: Fasciola
1. Fasciola hepatica , F. gigantica
2. Humans accidental definitive hosts
3. Metacercariae ingested from vegetation
4. Parasite migrates from intestine to liver; acute disease
5. Chronic infections when flukes reside in bile ducts
Nematodes-roundworms
1. Filamentous with cuticles, circular muscles, separate sexes
2. Complete digestive tract
Ascaris lumbricoides
1. Large (up to 30mm long) intestinal roundworm
2. 1 billion cases worldwide
3. Most cases in U.S. in southeast
4. Indigenous to humans
5. Spends larval and adult stages in humans and releases
embryonic eggs in feces, which are spread to other humans
6. Ingested eggs hatch into larvae and burrow through
intestine into circulation and travel to lungs & pharynx and
swallowed. Adult worms complete cycle in intestines.
7. Retain motility; don’t attach
Trichuris trichiura
1. Whipworm
2. Humans sole host
3. Hishest incidence in tropics
4. Remains in intestine
5. Worms can pierce capillaries, cause hemorrhage & allow
bacteria to leave intestine
Enterobius vermicularis
1. Pinworm
2. Most common worm disease of children in temperate zones
3. Humans are only host
4. Eggs picked up from surroundings and swallowed
5. Hatch in small intestine, develop into adults
6. Anal itching occurs when mature females emerge from
intestine to release eggs
V.
7. Self-inoculation common
8. Tape test
T. Hookworms
1. Curved ends, hooked mouths
2. Necator americanus, Ancylostoma duodenale
3. Humans shed eggs in feces, hatch into filariform larvae and
burrow into skin of lower legs
4. Larvae travel from blood to lungs, proceed up bronchi and
throat and are swallowed
5. Worms mature & reproduce in small intestine and complete
cycle
6. May cause pneumonia, nausea, vomiting, cramps, bloody
diarrhea, anemia
U. Strongyloides stercoralis
1. Threadworm
2. Life cycle in humans or moist soil
3. Larvae penetrate skin, migrate to lungs, swallowed,
complete development in intestine
4. Pneumonitis, eosinophilia, bloody diarrhea, liver
enlargement, bowel obstruction, malabsorption
Trichinella spiralis
1. Causes trichinosis
2. Life cycle entirely within mammalian host
3. Ingesting undercooked pork or bear meat
4. Larvae migrate from intestines to blood vessels, muscle,
heart, brain, where it forms cysts
5. First symptoms-flulike, diarrhea
6. Second symptoms- muscle & joint pain, shortness of
breath, pronounced eosinophilia
7. No cure after larva have encysted
W. Filarial worms
1. Tiny larvae circulate in blood and reside in
various organs
2. Spread by biting insects
X. Wuchereria bancrofti
1. Tropical infection spread by mosquitoes
2. Vector deposits larvae which move into lymphatics and
develop
3. Lymphatic filariasis is asymptomatic for years
4. Chronic infection causes blockage of lymphatic circulation &
elephantitis; usually in lower extremities
Y. Loa Loa
1. African eye worm
2. Spread by bite of small flies
3. Temperature-sensitive worm migrates around under skin and
may enter eye
4. Treatment-pull worm from a small hole or diethylcarbamazine