chapter 8

eukaryotic microorganisms

• protists

  • plant-like

  • fungi-like

  • animal-like

• fungi

protist characteristics

• unicellular

• 5 um to 5 mm

• decomposers

medical significance of protists

protists can be parasitic like malaria and toxoplasmosis and can also produce toxins

plant-like protists

• they do photosynthesis

• can have deadly toxins

fungus-like protist

• decomposers

• ex

  • water mold

    • related to algae, causes disease in marine stuff

  • slime mold

    • is a parasite of alge fungi and plants

animal-like protists

• some are commensals and some are parasitic

• ex

  • giardia causes diarrhea

  • amebozoa too

fungi

• digest dead organisms

• have lysosomal enzymes that digest damages cells and help to invade host

• not obligate parasite bc the host can be dead

• produce antibiotics to inhibit growth of other organisms

• can be pathogenic

mycoses (definition and 4 types)

• definition

  • a fungal disease that infects humans

• superficial

  • affects skin, hair, and nails

• subcutaneous

  • deeper skin layers and lymph vessels

• systemic

  • internal organs

• opportunistic

  • when hosts defenses are impaired

parasitic fungi characteristics

• proximity to host

• ability to penetrate host

• ability to digest and absorb nutrients from host cells

medical significance of fungi

• takes way longer to grow than bacteria, 2 to 4 weeks compared to 24 hours

• sometimes contamination is not seen in products for injection so the patients are only diagnosed months after

eukaryotic parasite

• a eukaryotic organism that lives at the expense of the host

• harder to kill parasite once in host bc they are the same domain and sometimes kingdom so it is also harmful to host

• more parasites than not parasites in nature

parasitology

study of the impact of parasites

found that 60 mil people die every year due to parasites infections and also infects crops —> land, money, starvation

ectoparasites

Live on the surface of other organisms

endoparasites

Live within the bodies of other organisms

Obligate parasites

Must spend some of their life cycle in or on a host like viruses

Facultative parasites

Normally can get nutrients from things other than hosts, but they can obtain nutrients from a host

Permanent parasites

Remain in or on host once they have invaded it

Temporary parasites

Feed on and then leave their host

like insects that bite

Accidental parasites

Invade an organism other than their normal host

ex: ticks spreading lyme disease when it is actually lives in deer and mice

vector

An organism that transfers a parasite to a new

host

Biological vector

A vector in which the parasite goes through

part of its life cycle —> so for obligate parasites

ex: malaria —> mosquito is a host and a vector for humans

Mechanical vector

A vector in which the parasite does not go

through any parts of its life cycle

ex: Flies that carry parasites eggs, bacteria, viruses from feces to human food

Hyperparasitism vector

When parasites have parasites

ex: mosquitos which are temporary parasites harbor the malaria parasite so they are also vectors

schizogony

one way for parasites to reproduce

Multiple fission in which on cell gives rise to

many cells

Hermaphrodite

way of parasite reproduction

One organism has both female and male reproductive systems and both are functional

how parasites change over evolution

• parasites tend to become less injurious to their host

  • guaranteed a continuous supply of nutrients

ways that parasites evade host defenses

• encystment

  • The formation of an outer covering that protects against unfavorable conditions.

    • also site for division and attaching parasite to host, or transmit

• change parasite surface antigens

  • Host can’t make new antibodies fast enough so the ones they have can’t target parasites antigens

• invade the actually cells

  • out of reach of the defense mechanism

damage that parasites can cause

• nutritional deprivation —> all do it

• tissue trauma

  • open sores, destroy cell tissues, damage vessels, cause hemorrhages

• immflame host and cause immunological reactions

parasitic worms

• flatworm

  • longer (up to 10m)

  • hemaphrodites

• roundworm

  • shorter (1m)

  • have males and females

• Both in intestinal track

arthropods as vectors

Ex: ticks, spiders, mites

• can live a long time off one bite

• ectoparasites

insects as vectors

ex: lice, fleas, mosquitos, flies that transmit parasites or feed on humans

crustaceans as vectors

crabs, crayfish