The Eukaryotic Members of the Microbial World

1
The Eukaryotic Members of the Microbial World

• Algae
• Protozoa
• Fungi
• Molds
• Arthropods and Helminths

2
Algae

• Eukaryotic cell structure
• Microscopic and macroscopic sizes
• Cell walls
• Part of a group of organisms called phytoplankton
  (primary producers in the oceans)

3
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.

4
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 (insteadsilicon, Ca etc.)
• Cilia, flagella, pseudopodia ? grouped acc. to
  mode of locomotion

5
Protozoan Reproduction

• Sometimes complex life cycles
• Protozoa can
• be polymorphic
• have vegetative (feeding) form trophozoite or
• resting form cyst
• Sexual or asexual reproduction

6
Protozoa and Human Disease

• Malaria (Plasmodium species)
• African sleeping sickness (Trypanosoma brucei)
• Toxoplasmosis (Toxoplasma gondii)
• Vaginitis (Trichomonas vaginalis)

7
Fungi

• Fungi are omnipresent
• 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

8
Fungal Disease in Humans

• Four types of fungal diseases
• Allergies
• Toxicities
• Mycoses
• Starvation due to food destruction
• Examples of fungal diseases
• Candida albicans (candidiasis)
• Cryptococcal meningoencephalitis
• Histoplasma capsulatum (Histoplasmosis)
• Pneumocystis carinii

9
Multicellular Parasites

• Arthropods and helminths medically important
• Arthropods do (most) damage as vetctors
• Helminths cause direct damage to host

10
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?

11
Allergic itchy rash
Scabies skin mite is about 0.4mm, just visible to
the human eye
Scabies skin mite is about 0.4mm, just visible to
the human eye
Sarcoptes scabei mite is about 0.4mm, just
visible to the human eye
12
Helminths

• Three groups of helminths relevant to medicine
• Nematodes (roundworms) GI tract or blood
  infections
• Cestodes (tapeworms)
• 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

13
Flat, segmented, scolex with suckers or hooks No
GI tract ? direct absorption of nutrients
14
Helminth Diseases

• Enterobiasis (Nematode - Enterobius vermicularis)
• Filariasis (Nematode - Wuchereria bancrofti)
• Tapeworm disease (Tania solium)
• Swimmers itch (Trematode - Cercaria sp.)

15
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.
16
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.
17
In their adult stage, filarial parasites live in
the lymph vessels The worms live for several
years, producing millions of very small, immature
larvae, microfilariae, that circulate in the
peripheral blood with marked nocturnal
periodicity.
18
Swimmers Itch - Cercarial Dermatitis
The schistosome cercaria (originating in specific
snail species) accidentally enters human skin.
Swimmers 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)
The End