Flashcards
Microbes & Disease - Lecture 25
Cards in this deck (50)
- 1Give 4 factors to describe Protozoa- Unicellular
- Eukaryotic
- Heterotroph
- Motile - 2Define a parasite.An organism that grows, feeds and is sheltered on or in a different organism while contributing nothing to the survival of its host.
- 3In what 3 ways can protozoa live/ survive?- Free living
- Parasitic
- Symbiotic - 4Approx. how many species of protozoa utilise humans as a host.30
- 5What is a primary host?A host in which parasites undergo sexual reproduction i.e. mosquito (malaria)
- 6What is meant by a secondary/ intermediate host?A host in which parasites undergo part of its life cycle, but not sexual reproduction.
i.e. humans (malaria) - 7List the main differences between Protozoa & Bacteria including the following factors: Cell size Prokaryotes/ Eukaryotes Location of DNA Reproduction Cytoplasm construction Flagella? Cell wallPROTOZOA
- 10 to 150 micrometres
- Eukaroytes
- DNA in nucleus
- Binary fission/ sexual reproduction
- Cytoplasm contains highly differentiated organelles
- Flagella & cilia consist of microtubules surrounded by plasma membrane.
- No cell wall
BACTERIA
- 1 to 10 micrometres
- Prokaryotes
- DNA free in cytoplasm
- Binary fission
- Cytoplasm undifferentiated
- Simple flagella
- Cell wall - 8What is meant by parallel evolution of bacteria & protozoa?- Organisms evolved for the same reason
- Different structures - 9Why is sexual reproduction so important in protozoa?- Genetic recombination during meiosis increases ability to adapt to changing conditions within hosts (immune pressure, drugs etc).
- 10What evidence is there that protozoa utilise Sexual Reproduction?- Direct observation e.g. some ciliates
- Genetic evidence - 11Describe our understanding of sexual reproduction in ciliates in comparison to Giardia.CILIATES
- Complex
- Well understood
GIARDIA
- Remains obscure - 12Describe the structure of microtubules in flagella and cilia.- Arranged in a geometric pattern of pairs
- 9 in a ring
- 2 in the middle
- Held by a basal body in the plasma membrane of protozoa
- Outer rings held to the inner rings via radial spoke.
- Each of the 9 rings are made up of an A tubule and a B tubule.
- Cylindrical tubes made of alpha and beta tubulin. - 13What are 4 common subtypes of Protozoa (including latin name). What features link to each of these protozoa?- Flagellates (Mastigophora) = Flagella
- Amoeba (Pseudopodia) = Pseudopodia
- Sporozoans (Sporozoae) = Apical microtubule complex (host cell invasion) & Sporozoites as part of life cycle.
- Ciliates (Ciliophora) = Cilia - 14Give 2 examples of Flagellates/ Mastigophora.- Giardia
- Trypanosoma - 15Give an example of Amoeba/ Pseudopodia.Entamoeba
- 16Give 2 examples of Sporozoans/ Sporozoae.Plasmodium
Toxoplasma - 17Give an example of a Ciliate/ Ciliophora.Balantidium
- 18Give an example of a Protozoa & Disease whose vector transmits it from human to human.- Plasmodium
- Malaria - 19Give an example of a Protozoa genus & Disease whose vector transmits it from animal to human (zoonotic).- Trypansoma > Trypansomiasis
- Leishmania > Leishmanisasis - 20Give an example of a Protozoa & Disease whose transmission is either via the Faecal oral (zoonosis), uncooked meat or from mother to child.Toxoplasma (sporozoan) > Toxoplasmosis
- 21Give 2 examples of Protozoa & Disease whose transmission is via the faecal oral (zoonosis) route.- Balantidium > Diarrhoea
- Cryptosporidium > Diarrhoea - 22Give an example of a Protozoa & Disease whose transmission is via the faecal oral route in humans.Giardia lamblia > Diarrhea
Entamoeba histolytica > Colitis & invasive disease - 23Give an example of a Protozoa & Disease who is transmitted sexually.Trichomonas vaginalis > Vaginitis
- 24What are the 3 causes of Entamoeaba histolytica and their percentage?- Asymptomatic colonisation - 90% of cases.
- Colitis (amoebic dysentery) - 10%
- Hepatic/ Pulmonary abscesses - 1% - 25How is Entamoeba histolytica transmitted?Human to human faecal-oral spread
- 26What is the 2-stage life cycle of Entamoeba histolytica?- Cyst
- Trophozoite - 27Describe the cysts which form in Entamoeba histolytica.- Passed with faeces
- Non motile
- Resistant to hostile environment
- Do not multiply - 28Describe the Trophozoites produced during infection with Entamoeba histolytica.- Metabolically active in the feeding stages.
- Motile
- Multiplies by replication - 29Describe how trophozoites in E. histolytica obtain nutrients from the host.- Phagocytosis of bacteria and host cells.
- Fusion with lysosome containing enzymes
- Absorption of nutrients into cytoplasm. - 30How do trophozoites travel? (motile)Pseudopodia
- 31How do trophozoites replicate?- Binary fission
- Possibly sexual reproduction - 32Describe the movement of protozoa with pseudopodia.- Temporary projections of the cell wall through reversible assembly of microfilaments in the cytoplasm.
- Microfilaments form from contractile actin protein fibers cell contraction, gliding movements & cytokinesis. - 33Describe what Encystment involves, and when it might occur in fecal-oral pathogens.- Secretion of a protective covering
- Deactivation of metabolic & anabolic pathways
- Dissolution of organelles
- During desiccation
- During decreased oxygen concentration - 34Describe what Excystation involves, and when it might occur in fecal-oral pathogens.- Re-differentiation of organelles
- Reactivation of metabolic and anabolic pathways.
- Triggered by enzymes of pancreatic juices. - 35What is Amoebic Dysentery?Dysentery caused by infection of the intestines by the protozoan Entamoeba histolytica.
- 36Why does E. histolytica invade, but E. dispar (another Amoeba) not invade?VIRULENCE FACTORS
- 37How does E. histolytica bind to ECM?Gal/ GalNac- specific lectin.
- 38How does E. histolytica destroy the mucous layer?EhCP (E. histolytica Cystein Protease)
- 39How does E. histolytica subvert the immune response once they have destroyed the mucous layer of cells?- Degradation of reactive oxygen species by superoxide dismutase.
- Contact dependent cytolysis. - 40Once E. histolytica has degraded reactive oxygen species, how do they rid themselves of their antigens to avoid detection by the immune system?- Capping and shedding
- Cytoskeletal rearrangement to move antigens to specific area for shedding. - 41Once antigens have been shedded, how do E. histolytica activate host cell apoptosis pathway?They release an active peptide amoebapor A into the attached host cell which activates this pathway.
Contact dependent lysis. - 42What happens once E. histolytica have actively secreted Amoebapor A into host cell?Host cell death.
Phagocytosis. - 43What determines the success/ length of the E. histolytica invasion/ evasion process?- Predisposition to invasion - Host = HLA type & nutritional status, Pathogen = Certain E. histolytica genotype invading.
- Gut microenvironment may delay invasion by months. - 44What are 6 current research methods for study of E. histolytica?- Phagocytosis assay
- Migration assay
- Human colonic explant model
- Cytotoxicity assay
- Motility assay
- Host cell adhesion assay
- Host cell monolayer destruction - 45What are recent advances with the Human Nutrition Hormone Leptin?- Human population genetic polymorphism studies.
- Animal model studies.
- Genetic differences within single infected humans between hepatic and colonic amoeba.
- Trialled in baboons that by delivering a Gal-lectin subunit (vaccine) in the mucous, you protect the organism from infection. - 46What is meant by enteric?Relating to the intestines
- 47What type of protozoa is Giardia lamblia?- Flagellated
- Enteric
- Non-invasive - 48Briefly describe the life cycle of Giardia lamblia.- Cysts & trophozoites passed in stools.
- Cysts survive and pass into food/ water and contaminate.
- These cysts can then be ingested by another human and go on to infect the intestines whereby trophozoites absorb nutrients from the host & divide. - 49Describe how Giardia lamblia go about infection in the intestines.- Adhere to intestinal epithelial cells.
- Disruption of brush border in small intestine > disruption of absorption (thus, diarrhoea) > allows nutrient absorption.
- No evidence of invasion - 50What part of the Giardia lamblia adhere to the small intestine?Ventral site (belly)