Flashcards in 3 Microbiology: Protozoa Deck (83)
What are Protozoa/Protozoan?
are unicellular eukaryotic organisms that lack cell walls
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
A large number of protozoa are part of?
the normal microbiota of humans and animals
What do protozoa feed on? (Nutrition)
feed upon bacteria and small particulate or macromolecular materials
some ingest tissue cells of the host
What is a pellicle?
a protective covering on protozoa which prevents transport of nutrients across the plasma membrane
amoebas engulf food by?
surrounding it with pseudopodia and phagocytizing it
cilates engulf food by?
waving cilia toward a mouthlike opening
What is a cytostome?
mouthlike opening on ciliates
What is a food vacuole?
membrane-enclosed place where food is digested in ALL protozoa
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
How do protozoa reproduce?
many protozoa are able to reproduce both sexually and asexually
in some only asexual occurs
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
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.
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
What is a schizont?
the dividing form in schizogony
What are merozoites?
the daughter forms in schizogony
What is conjugation?
the form of sexual reproduction in ciliates
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
What are the two nuclei in ciliates?
What is syngamy?
protozoa produce gametes
during reproduction, a microgamete fuses with a macrogamete to form a diploid zygote
What are microgamete?
What are macrogamete?
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
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.
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
What are the Major groups of protozoa?
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
spindle shaped with flagella projecting from the front end
most have two or more flagella
flagella also serve as food-capturing organelles
What are mucosoflagellate?
are found in the lumen of the intestine and other mucosal sites
are found in blood, lymph, or tissue fluids
name some common flagellates
What are Ciliates (Ciliophora)?
are protozoa that in some stage of their life cycle, possess cilia that are similar to but shorter than flagella
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)
What is a micronucleus?
nucleus in ciliates which is involved in sexual production
What is a macronucleus?
nucleus in ciliates which is only involved with protein synthesis and other ongoing cellular activities
Name some common ciliates
What are Amoebas (Sarcondinas)?
are parasites to humans and other vertebrates, and their usual habitat is the oral cavity or the intestinal tract
How do Amoebas move?
move by pseudopods- can flow from one side and the rest of the cell will flow towards the pseudopods
What are pseudopods?
blunt, lobe-like projections of the cytoplasm
amoebas are always this in the vegetative phase?
What are foraminefera?
amoebas which secrete a shell during vegetative stage
What are pseudopodia?
are the locomotor or food-capturing organelles
Name some some common amoebas
What are Apicomplexa (Sporozoans)?
comprise a large group of protozoa, ALL of which are obligate intracellular parasites and cause disease by destroying those cells
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
What are sporozoites?
produced by apicomplexa and are not true resting spores but produce analogous structures
What is an apical complex?
a complex of special organelles at the anterior ends to assist in penetrating cells
What does the apical complex consist of?
consists of an apical conoid, rhoptries, and cortical microtubules
What is an apical conoid?
conical structure in the apical complex
enable the parasite to bore its way through the cell membrane
What are rhoptries?
sac-like orgenelles in the apical complex
secrete enzymes that penetrate the host's tissues
What are cortical microtubules?
extend backwards from the apical complex to support the surface of the organism (elongated form of the body)
Describe the Apicomplexa life cycle
some species require a definite and intermediate host
some may use a paratenic host (blood sucking arthropods)
example of a apicomlexa that requires a definite and intermediate host
example of a apicomlexa that use a paratenic host
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
What is the site of infection for apicomplexas?
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
intracellular organisms primarily of eurythrocytes but some multiply in leukocytes or in cells of many organs
Name examples of apicomplexas
Sarcocystic neurona (EPM)
infections by parasitic protozoa are?
are long lasting and chronic and individual parasites may persist in a host for long periods of time
A factor that determines the outcome of an interaction between parasite and host is?
is the inoculum size
What is the inoculum size?
a minimum number of organisms is required to establish infection
Host spectrum of protozoa
infect all vertebrate hosts: dogs, cats, equine, livestock, humans, etc
some are highly host specific
others have broad host range
Protozoan parasites are almost always acquired from?
an exogenous source
transmission of protozoan diseases is frequently facilitated by?
environmental contamination with human and animal wastes
What are the most common modes of entry?
direct penetration through the skin or other surfaces
transplacental infection occurs in a number of diseases such as...
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)
Most infections are initiated by?
attachment of the organism to host tissues
followed by replication to establish colonization
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)
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
2 ways most protozoa replicate in the host
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
enzymes secreted and release on the destruction of the parasites can cause what?
host cell destruction
gross tissue pathology
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
for the disease process to be maintained the parasite must be able to?
evade the host's immune defense system
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
examples of antigenic variation
Plasmodium, Babesia, and Giardia species (similar seen in these)
Describe antigen masking
some protozoan parasites acquire host molecules that conceal the antigenic site, thus preventing immune recognition
immunosuppression is often observed during?
is often observed during the course of some protozoan infections (malaria)
Describe intracellular location
many protozoan parasites evade immune responses in the host here
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.
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
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