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Flashcards in 3 Microbiology: Protozoa Deck (83):
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What are Protozoa/Protozoan?

are unicellular eukaryotic organisms that lack cell walls

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Name properties of protozoa

are free living and are found in soil and in a variety of freshwater and marine habitats
are motile and chemoheterotrophic
food is digested within a food vacuole
osmotic pressure is regulated by the contractile vacuole (eliminates excess water)
mostly aerobic, except intestinal can grow anaerobically

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A large number of protozoa are part of?

the normal microbiota of humans and animals

3

What do protozoa feed on? (Nutrition)

feed upon bacteria and small particulate or macromolecular materials
some ingest tissue cells of the host

4

What is a pellicle?

a protective covering on protozoa which prevents transport of nutrients across the plasma membrane

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amoebas engulf food by?

surrounding it with pseudopodia and phagocytizing it

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cilates engulf food by?

waving cilia toward a mouthlike opening

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What is a cytostome?

mouthlike opening on ciliates

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What is a food vacuole?

membrane-enclosed place where food is digested in ALL protozoa

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What are the three was Protozoa excrete waste products?

may occur directly through the plasma membrane
by means of contractile vacuoles through the cell wall
a specialized anal pore

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How do protozoa reproduce?

many protozoa are able to reproduce both sexually and asexually
in some only asexual occurs

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What is binary fission?

the most common asexual reproduction among protozoa
two daughter cells result from a "parent" cell, division occurring mostly along the longitudinal axis or ocassionally, across the transverse plane
the nucleus divides first, followed by cytoplasmic division

12

What is Budding?

is a process in which two or many daughter forms are produced by the "parent cell"
there is usually and unequal fragmentation of the nucleus and the cytoplasm, but the forms are separated off and then grow to full size.

13

What is schizogony (multiple fission)?

the nucleus undergoes multiple divisions before the cell divides.
after many nuclei are formed, each nucleus becomes associated with a portion of cytoplasm and little or nothing of the parent cell remains except the greatly expanded limiting membrane.
the single cell then separates into daughter cells

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What is a schizont?

the dividing form in schizogony

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What are merozoites?

the daughter forms in schizogony

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What is conjugation?

the form of sexual reproduction in ciliates

17

Describe what happens during conjugation

two organisms pair and the micronucleus from each organism migrates to the other organism.
the micronucleus fuses with the macronucleus within the organism,
the parent organisms separate, each now is a fertilized cell.
both organisms will later divide, producing two daughter cells with recombinant DNA.
the nucleus divides to give rise to a new macronucleus and micronucleus

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What are the two nuclei in ciliates?

macronucleus
micronucleus

19

What is syngamy?

protozoa produce gametes
during reproduction, a microgamete fuses with a macrogamete to form a diploid zygote

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What are microgamete?

male gamete

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What are macrogamete?

female gamete

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What is sporogony?

an asexual process of multiple fission
follows syngamy, and a number of sporozoites are formed within the walls of a cyst from the zygote

23

What is encystment?

the cell may assume a fairly round or oval shape and secrete a protective capsule around itself under certain adverse environmental conditions.
during this the cell may survive a lack of food or moisture, adverse temperature changes, or contact with toxic chemical agents.

24

The cyst from encystment is valuable because?

allowing parasitic forms to survive outside the host until they can enter a new host.
when favorable conditions arise, water is absorbed, and organism emerges and can resume growth

25

What are the Major groups of protozoa?

flagellates (mastigophora)
ciliates (ciliophora)
amoebas (Sarcodinas)
apicomplexa (sporozoans)

26

Describe flagellates (mastigophora)

members of this group are motile by the action of flagella
many are free-living organisms
many are parasitic in, or pathogenic for animals and humans

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flagellate characteristics

spindle shaped with flagella projecting from the front end
most have two or more flagella
flagella also serve as food-capturing organelles
mostly extracellular

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What are mucosoflagellate?

are found in the lumen of the intestine and other mucosal sites
-Giardia

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What arenhemoflagellates?

are found in blood, lymph, or tissue fluids
-Trypanosoma

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name some common flagellates

Trypanosoma
Giardia
Leishmania
Trichomona

31

What are Ciliates (Ciliophora)?

are protozoa that in some stage of their life cycle, possess cilia that are similar to but shorter than flagella

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ciliates characteristics

cilia are arranged in precise rows on the cell and are used for motility and to bring food to the mouth
have two kinds of nuclei- the micronucleus and macronucleus (unique)
few are parasitic for animals
a number of obligated anaerobic are beneficial (animal digestion i.e. cow rumen)

33

What is a micronucleus?

nucleus in ciliates which is involved in sexual production

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What is a macronucleus?

nucleus in ciliates which is only involved with protein synthesis and other ongoing cellular activities

35

Name some common ciliates

Paramecium
Balantidium

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What are Amoebas (Sarcondinas)?

are parasites to humans and other vertebrates, and their usual habitat is the oral cavity or the intestinal tract

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How do Amoebas move?

move by pseudopods- can flow from one side and the rest of the cell will flow towards the pseudopods

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What are pseudopods?

blunt, lobe-like projections of the cytoplasm

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amoebas are always this in the vegetative phase?

naked

40

What are foraminefera?

amoebas which secrete a shell during vegetative stage

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What are pseudopodia?

are the locomotor or food-capturing organelles

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Name some some common amoebas

Entamoeba
Amoeba

43

What are Apicomplexa (Sporozoans)?

comprise a large group of protozoa, ALL of which are obligate intracellular parasites and cause disease by destroying those cells

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Apicomplexa characteristics

produce sporozoites
lack of motile adult stages- gametes are motile
food is generally not ingested but instead is absorbed in soluble form through the body wall
apical complex to assist in penetrating cells

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What are sporozoites?

produced by apicomplexa and are not true resting spores but produce analogous structures

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What is an apical complex?

a complex of special organelles at the anterior ends to assist in penetrating cells

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What does the apical complex consist of?

consists of an apical conoid, rhoptries, and cortical microtubules

48

What is an apical conoid?

conical structure in the apical complex
enable the parasite to bore its way through the cell membrane

49

What are rhoptries?

sac-like orgenelles in the apical complex
secrete enzymes that penetrate the host's tissues

50

What are cortical microtubules?

extend backwards from the apical complex to support the surface of the organism (elongated form of the body)

51

Describe the Apicomplexa life cycle

complex
some species require a definite and intermediate host
some may use a paratenic host (blood sucking arthropods)

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example of a apicomlexa that requires a definite and intermediate host

Toxoplasma gondii

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example of a apicomlexa that use a paratenic host

Hemosporidian

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What is a paratenic host?

a host that is not essential for the development of a parasite but which can transmit parasite, ensuring its widespread dissemination

55

What is the site of infection for apicomplexas?

In coccidia:
in definite hosts- multiply mainly in epithelial and other cells of the intestine
in intermediate hosts- multpilication may occur in several extra-intestinal sites depending on species
In hemosporidians
intracellular organisms primarily of eurythrocytes but some multiply in leukocytes or in cells of many organs

56

Name examples of apicomplexas

Cryptosporidium
Plasmodium
Toxoplasma
Coccidia
Babesia
Sarcocystic neurona (EPM)

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infections by parasitic protozoa are?

are long lasting and chronic and individual parasites may persist in a host for long periods of time

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A factor that determines the outcome of an interaction between parasite and host is?

is the inoculum size

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What is the inoculum size?

a minimum number of organisms is required to establish infection

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Host spectrum of protozoa

infect all vertebrate hosts: dogs, cats, equine, livestock, humans, etc
some are highly host specific
others have broad host range

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Protozoan parasites are almost always acquired from?

an exogenous source

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transmission of protozoan diseases is frequently facilitated by?

environmental contamination with human and animal wastes

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What are the most common modes of entry?

oral ingestion
direct penetration through the skin or other surfaces

64

transplacental infection occurs in a number of diseases such as...

Toxoplasma gondii

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Why is route of exposure critical for most organisms?

Pathogenic strain can be unlikely to cause disease if it does not enter host through which would cause disease.
(A pathogenic strain of Entamoeba histolytica exposed through skin s unlikely to cause disease but if it is through oral ingestion may cause severe dysentery)

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Most infections are initiated by?

attachment of the organism to host tissues
followed by replication to establish colonization

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The life cycle of a protozoan is based on?

species and tissue tropisms
(determine the organs or tissues of the host in which the protozoan can survive)

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The attachment of the parasite to host cells or tissues

may be mediated by mechanical or biting mouth parts
the interaction between adhesins on the parasite surface and specific glycoprotein or glycolipid receptors on the cell membrane

69

2 ways most protozoa replicate in the host

intracellularly
extracellularly

70

the pathologic mechanisms, lesions, clinical signs, and symptoms associated with disease may be a consequence of?

both the parasite and the host reaction to it

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enzymes secreted and release on the destruction of the parasites can cause what?

host cell destruction
inflammatory responses
gross tissue pathology

72

the extent of the injury may be influenced by what.

size and number of parasites
how the parasite feed or derives its nutrients
the extent of parasite migration
etc.

73

for the disease process to be maintained the parasite must be able to?

evade the host's immune defense system

74

Describe antigenic variation

some organisms can shift antigenic expression
Rapid variation of expression of antigens in the glycocalyces of these organisms occurs each time that the host mounts a new humoral (antibody) response

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examples of antigenic variation

African trypanosomes
Plasmodium, Babesia, and Giardia species (similar seen in these)

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Describe antigen masking

some protozoan parasites acquire host molecules that conceal the antigenic site, thus preventing immune recognition

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immunosuppression is often observed during?

is often observed during the course of some protozoan infections (malaria)

78

Describe intracellular location

many protozoan parasites evade immune responses in the host here

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A variety of methods the organisms that reside in macrophages have developed to avoid intracellular killing

prevention of phagolysosome fusion
resistance to killing after exposure to lysosomal enzymes
escape of phagocytosed cells from the phagosome into the cytoplasm with subsequent replication of the organism.

80

Describe Toxoplasma gondii (mechanisms to avoid intracellular killing)

1. dead parasite in phagosome- fusion with lysosome
2 live parasite in endosome- no fusion with lysosome

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Describe Trypanosoma cruzi (mechanisms to avoid intracellular killing)

1. parasite killed in phagosome following lysosomal fusion
2. parasites escape phagosome and divide free in cytoplasm

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Describe Leishmania (mechanisms to avoid intracellular killing)

1. parasites resist lysosomal enzyme and divide inside phagosome

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