The Eukaryotic Members
of the
Microbial World
Algae
Protozoa
Fungi
Molds
Arthropods and Helminths
Algae
• Eukaryotic cell structure
• Microscopic and macroscopic
sizes
• Cell walls
• Part of a group of organisms
called phytoplankton (primary
producers in the oceans)
Algal Toxicity
Red tides caused by
• G. breve now K. brevis (Karenia brevis ): Brevetoxin kills fish
feeding on phytoplankton and causes illness in ho and
animals. (Famous Florida red tides).
• Gonyaulax: neurotoxins that accumulates in shellfish
(immune to it) cause paralytic shellfish poisoning in
ho and animals. Death possible.
Protozoa
• Protozoan habitats
– Mostly free – living, some parasitic
– In marine (zooplankton) , fresh water and
terrestrial environments
• Structure of protozoa
– Microscopic, unicellular, no chlorophyll
– No cellulose cell wall (instead
silicon, Ca etc.)
– Cilia, flagella, pseudopodia  grouped acc. to
mode of locomotion
Protozoan Reproduction
• Sometimes complex life cycles
• Protozoa can
– be polymorphic
– have vegetative (feeding) form = trophozoite
or
– resting form = cyst
• Sexual or asexual reproduction
Protozoa and Human Disease
• Malaria (Plasmodium
species)
• African sleeping sickness
(Trypanosoma brucei)
• Toxoplasmosis
(Toxoplasma gondii)
• Vaginitis (Trichomonas
vaginalis)
Fungi are omnipresent
Fungi
Structure of fungi (yeasts, molds and mushrooms)
Only few fungi cause disease in animals (mostly
in immunocompromised individuals)
Economic importance
–
–
–
–
wine, beer, bread, and cheese production
Antimicrobial medicines
Biotechnology
Many plant pathogens
Fungal Disease in Humans
Four types of fungal diseases
1. Allergies
2. Toxicities
3. Mycoses
4. Starvation due to food destruction
Examples of fungal diseases
• Candida albicans (candidiasis)
• Cryptococcal meningoencephalitis
• Histoplasma capsulatum (Histoplasmosis)
• Pneumocystis carinii
Multicellular Parasites
• Arthropods and helminths medically important
• Arthropods do (most) damage as vetctors
• Helminths cause direct damage to host
Arthropods
• Arthropod borne diseases - Mechanical
vectors (flies etc.) vs. biological vectors
• Insects: Mosquitoes, fleas and lice
• Arachnids: Ticks and mites (mites cause direct
disease, e.g.: scabies)
• Example diseases
– Yellow fever – Mosquito - Flavivirus
– Rocky mountain spotted fever – tick – Rickettsia
– Other “famous” examples?
Helminths
Three groups of helminths relevant to medicine
1. Nematodes (roundworms): GI tract or blood
infections
2. Cestodes (tapeworms)
3. Trematodes (flukes)
Three modes of human invasion:
- Skin penetration
- Contaminated food
- Insect vector
Under control in developed countries, millions of deaths /
year in underdeveloped countries
Helminth Diseases
• Enterobiasis (Nematode - Enterobius vermicularis)
• Filariasis (Nematode - Wuchereria bancrofti)
• Tapeworm disease (Tania solium)
• Swimmer’s itch (Trematode - Cercaria sp.)
Enterobiasis
One of the most common
parasitic infections of humans.
Causative agent: Pinworm
(Enterobius vermicularis)
10% to 40% of children (below
age 12) are infected.
Adult pinworms are white and
are less than one half inch long,
with the diameter of a strand of
thread. The adult worms live in
the colons of human children
and feed on human fecal
matter.
Approximately 120 million people are infected. 90% are caused by Wuchereria
bancrofti. Almost 25 million men suffer from genital disease (most commonly
hydrocoele); an estimated 15 million people have lymphoedema or elephantiasis
of the leg.
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In their adult stage, filarial parasites live
in the lymph vessels
u
The worms live for several years, producing
millions of very
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small, immature larvae, microfilariae,i that circulate in the
n
peripheral blood with marked nocturnal periodicity.
Swimmer’s Itch - Cercarial Dermatitis
The schistosome cercaria (originating in
specific snail species) accidentally enters
human skin.
Swimmer’s itch cases have been reported
from nearly every state. (Most predominant
in the north). In addition, swimmer's itch
has been reported from more than 30
countries.
Disappears without treatment (after up to 7
days)